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Sample records for frequency oxygen plasma

  1. Atomic Oxygen Energy in Low Frequency Hyperthermal Plasma Ashers

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Miller, Sharon K R.; Kneubel, Christian A.

    2014-01-01

    Experimental and analytical analysis of the atomic oxygen erosion of pyrolytic graphite as well as Monte Carlo computational modeling of the erosion of Kapton H (DuPont, Wilmington, DE) polyimide was performed to determine the hyperthermal energy of low frequency (30 to 35 kHz) plasma ashers operating on air. It was concluded that hyperthermal energies in the range of 0.3 to 0.9 eV are produced in the low frequency air plasmas which results in texturing similar to that in low Earth orbit (LEO). Monte Carlo computational modeling also indicated that such low energy directed ions are fully capable of producing the experimentally observed textured surfaces in low frequency plasmas.

  2. Influence of oxygen traces on an atmospheric-pressure radio-frequency capacitive argon plasma discharge

    SciTech Connect

    Li Shouzhe; Wu Qi; Yan Wen; Wang Dezhen; Uhm, Han S.

    2011-10-15

    An atmospheric-pressure capacitive discharge source driven by radio-frequency power supply at 13.56 MHz has been developed experimentally that is capable of producing a homogeneous and cold glow discharge in O{sub 2}/Ar. With respect to the influence of oxygen component when diluted into argon plasma discharge on the discharge characteristics, the measurements of the electrical parameters (impedance, phase angle, resistance, and reactance) are made systematically and the densities of the metastable and resonant state of argon are determined by means of optical emission spectroscopy (OES). It is shown that the admixture of oxygen into argon plasma not only changes the electric characteristics but also alters the optical emission spectra greatly due to strong interaction between the oxygen content and the argon in the plasma environment.

  3. Improvement of photocatalytic activity of silver nanoparticles by radio frequency oxygen plasma irradiation

    NASA Astrophysics Data System (ADS)

    Fang, Yingcui; Zhang, Bing; Hong, Liu; Yao, Damao; Xie, Zhiqiang; Jiang, Yang

    2015-07-01

    Photocatalytic activity (PA) of silver nanoparticles (AgNPs) induced by radio frequency (RF) oxygen plasma irradiation (OPI) is investigated in this paper. An improvement in PA by 365% and 181% has been achieved when 15 nm AgNPs irradiated by oxygen plasma for 2 s were used to degrade 10-5 M Rhodamine 6 G (R6G) under ultraviolet (UV) and visible lights, respectively. The PA caused by OPI is better than that induced by the localized surface plasma resonance (LSPR) of AgNPs. The mechanism for the improvement was explored by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectra. The OPI-induced formation of AgO/AgNP and Ag2O/AgNP-heterogeneous photocatalysts and electrophilic oxygen are considered to be responsible for the PA improvement. This investigation deepens our understanding of oxygen-assisted photocatalysis of AgNPs and provides a practical approach using solar light for broad spectra photocatalysis with high efficiency.

  4. Treatment of Second-Order Structures of Proteins Using Oxygen Radio Frequency Plasma

    NASA Astrophysics Data System (ADS)

    Hayashi, Nobuya; Nakahigashi, Akari; Liu, Hao; Goto, Masaaki

    2010-08-01

    Decomposition characteristics of second-order structures of proteins are determined using an oxygen radio frequency (RF) plasma sterilizer in order to prevent infectious proteins from contaminating medical equipment in hospitals. The removal of casein protein as a test protein with a concentration of 50 mg/cm2 on the plane substrate requires approximately 8 h when singlet atomic oxygen is irradiated. The peak intensity of Fourier transform infrared spectroscopy (FTIR) spectra of the β-sheet structures decreases at approximately the same rate as those of the α-helix and first-order structures of proteins. Active oxygen has a sufficient oxidation energy to dissociate hydrogen bonds within the β-sheet structure.

  5. Osteoblast behavior on polytetrafluoroethylene modified by long pulse, high frequency oxygen plasma immersion ion implantation.

    PubMed

    Wang, Huaiyu; Kwok, Dixon T K; Wang, Wei; Wu, Zhengwei; Tong, Liping; Zhang, Yumei; Chu, Paul K

    2010-01-01

    Polytetrafluoroethylene (PTFE) is a commonly used medical polymer due to its biological stability and other attractive properties such as high hardness and wear resistance. However, the low surface energy and lack of functional groups to interact with the cellular environment have severely limited its applications in bone or cartilage replacements. Plasma immersion ion implantation (PIII) is a proven effective surface modification technique. However, when conducted on polymeric substrates, conventional PIII experiments typically employ a low pulsing frequency and short pulse duration in order to avoid sample overheating, charging, and plasma sheath extension. In this paper, a long pulse, high frequency O(2) PIII process is described to modify PTFE substrates by implementing a shielded grid in the PIII equipment without these aforementioned adverse effects. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurements are carried out to reveal the surface effects of PTFE after long pulse, high frequency O(2) PIII and the results are compared to those obtained from conventional short pulse, low frequency O(2) PIII, O(2) plasma immersion, and the untreated control samples. Our results show that less oxygen-containing, rougher, and more hydrophobic surfaces are produced on PTFE after long pulse, high frequency O(2) PIII compared to the other 2 treatments. Cell viability assay, ALP activity test, and real-time PCR analysis are also performed to investigate the osteoblast behavior. It is clear that all 3 surface modification techniques promote osteoblast adhesion and proliferation on the PTFE substrates. Improvements on the ALP, OPN, and ON expression of the seeded osteoblasts are also obvious. However, among these treatments, only long pulse, high frequency O(2) PIII can promote the OCN expression of osteoblasts when the incubation time is 12 days. Our data unequivocally disclose that the long pulse, high frequency O(2) PIII

  6. Real time sensor for monitoring oxygen in radio-frequency plasma applications.

    PubMed

    Milosavljevic, Vladimir; Faulkner, R; Hopkins, M B

    2007-10-17

    Real time closed loop control of plasma assisted semiconductor manufacturing processes has received significant attention in recent years. Therefore we have developed and tested a customized optical sensor based on buffer gas (argon) actinometry which has been used to determine relative densities of atomic and molecular oxygen in an Ar/O(2) radio-frequency ICP chamber. The operation and accuracy of our optical sensor compared favorably with a high resolution commercial spectrometer but at lower cost and exhibited improved actinometric performance over a low resolution commercial spectrometer. Furthermore, threshold tests have been performed on the validity of buffer gas based actinometry in Ar/O(2) ICP plasmas where Ar is no longer a trace gas through Xe actinometry. The plasma conditions for which this customized optical sensor can be used for closed loop control have been established.

  7. Particle modelling of magnetically confined oxygen plasma in low pressure radio frequency discharge

    SciTech Connect

    Benyoucef, Djilali; Yousfi, Mohammed

    2015-01-15

    The main objective of this paper is the modelling and simulation of a radio frequency (RF) discharge in oxygen at low pressure and at room temperature, including the effect of crossed electric and magnetic fields for generation and confinement of oxygen plasma. The particle model takes into account one axial dimension along the electric field axis and three velocity components during the Monte Carlo treatment of the collisions between charged particles and background gas. The simulation by this developed code allows us not only to determine the electrodynamics characteristics of the RF discharge, but also to obtain kinetics and energetic description of reactive oxygen plasma at low pressure. These information are very important for the control of the deep reactive-ion etching technology of the silicon to manufacture capacitors with high density and for the deposition thick insulating films or thick metal to manufacture micro-coils. The simulation conditions are as follows: RF peak voltage of 200 V, frequency of 13.56 MHz, crossed magnetic field varying from 0 to 50 Gauss, and oxygen pressure of 13.8 Pa. In the presence of magnetic field, the results show an increase of the plasma density, a decrease of the electron mean energy, and also a reduction of the ratio between electron density and positive ion density. Finally in order to validate, the results are successfully compared with measurements already carried out in the literature. The conditions of comparison are from 100 to 300 V of the peak voltage at 13.56 MHz under a pressure of 13.8 Pa and a gap distance of 2.5 cm.

  8. Plasma processing of ? in a hydrogen/oxygen radio-frequency discharge

    NASA Astrophysics Data System (ADS)

    Turcicová, H.; Perina, V.; Vacík, J.; Cervená, J.; Zemek, J.; Zelezný, V.; Arend, H.

    1998-05-01

    Monocrystalline 0022-3727/31/9/004/img10 was processed in a radio-frequency (27.12 MHz) discharge in hydrogen and subsequently in oxygen and the composition of the thus produced surface layers evaluated. The hydrogen plasma treatment caused a heavy blackening of the sample due to chemical reduction. At low 0022-3727/31/9/004/img11 pressures (0022-3727/31/9/004/img12 Torr) the niobate structure on the sample surface was completely destroyed; only niobium and its oxides remained on the surface. At higher pressures (0022-3727/31/9/004/img13 Torr) the niobate structure was preserved. Hydrogenation of the surface layer was found which persisted up to 5000022-3727/31/9/004/img14C. Subsequent treatment in an oxygen plasma under similar processing conditions brought about the restoration of the transparency of the sample. The following methods were used for the modified surface structure analysis: neutron depth profiling, Rutherford backscattering, x-ray photoelectron spectroscopy and VIS and IR spectrometry.

  9. The effect of oxygen flow rate and radio frequency plasma power on cubic ZnMgO ultraviolet sensors grown by plasma-enhanced molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Casey Boutwell, R.; Wei, Ming; Schoenfeld, Winston V.

    2013-07-01

    Cubic Zn1-xMgxO thin films were produced by Plasma-Enhanced Molecular Beam Epitaxy. Oxygen flow rate and applied Radio-Frequency (RF) plasma power were varied to investigate the impact on film growth and optoelectronic device performance. Solar-blind and visible-blind detectors were fabricated with metal-semiconductor-metal interdigitated Ni/Mg/Au contacts and responsivity is compared under different growth conditions. Increasing oxygen flow rate and RF plasma power increased Zn incorporation in the film, which leads to phase segregation at relatively high Zn/Mg ratio. Responsivity as high as 61 A/W was measured in phase-segregated ZnMgO visible-blind detectors.

  10. On the E-H transition in inductively coupled radio frequency oxygen plasmas: I. Density and temperature of electrons, ground state and singlet metastable molecular oxygen

    NASA Astrophysics Data System (ADS)

    Wegner, Th; Küllig, C.; Meichsner, J.

    2017-02-01

    In this series of two papers, the E-H transition in a planar inductively coupled radio frequency discharge (13.56 MHz) in pure oxygen is studied using comprehensive plasma diagnostic methods. The electron density serves as the main plasma parameter to distinguish between the operation modes. The (effective) electron temperature, which is calculated from the electron energy distribution function and the difference between the floating and plasma potential, halves during the E-H transition. Furthermore, the pressure dependency of the RF sheath extension in the E-mode implies a collisional RF sheath for the considered total gas pressures. The gas temperature increases with the electron density during the E-H transition and doubles in the H-mode compared to the E-mode, whereas the molecular ground state density halves at the given total gas pressure. Moreover, the singlet molecular metastable density reaches 2% in the E-mode and 4% in the H-mode of the molecular ground state density. These measured plasma parameters can be used as input parameters for global rate equation calculations to analyze several elementary processes. Here, the ionization rate for the molecular oxygen ions is exemplarily determined and reveals, together with the optical excitation rate patterns, a change in electronegativity during the mode transition.

  11. Energetic electron avalanches and mode transitions in planar inductively coupled radio-frequency driven plasmas operated in oxygen

    SciTech Connect

    Zaka-ul-Islam, M.; Niemi, K.; Gans, T.; O'Connell, D.

    2011-07-25

    Space and phase resolved optical emission spectroscopic measurements reveal that in certain parameter regimes, inductively coupled radio-frequency driven plasmas exhibit three distinct operation modes. At low powers, the plasma operates as an alpha-mode capacitively coupled plasma driven through the dynamics of the plasma boundary sheath potential in front of the antenna. At high powers, the plasma operates in inductive mode sustained through induced electric fields due to the time varying currents and associated magnetic fields from the antenna. At intermediate powers, close to the often observed capacitive to inductive (E-H) transition regime, energetic electron avalanches are identified to play a significant role in plasma sustainment, similar to gamma-mode capacitively coupled plasmas. These energetic electrons traverse the whole plasma gap, potentially influencing plasma surface interactions as exploited in technological applications.

  12. Low Pressure Radio-Frequency Oxygen Plasma Induced Oxidation of Titanium – Surface Characteristics and Biological Effects

    PubMed Central

    Tseng, Wan-Yu; Hsu, Sheng-Hao; Huang, Chieh-Hsiun; Tu, Yu-Chieh; Tseng, Shao-Chin; Chen, Hsuen-Li; Chen, Min-Huey; Su, Wei-Fang; Lin, Li-Deh

    2013-01-01

    Objective This research was designed to investigate the effects of low pressure radio-frequency (RF) oxygen plasma treatment (OPT) on the surface of commercially pure titanium (CP-Ti) and Ti6Al4V. Surface topography, elemental composition, water contact angle, cell viability, and cell morphology were surveyed to evaluate the biocompatibility of titanium samples with different lengths of OP treating time. Materials and Methods CP-Ti and Ti6Al4V discs were both classified into 4 groups: untreated, treated with OP generated by using oxygen (99.98%) for 5, 10, and 30 min, respectively. After OPT on CP-Ti and Ti6Al4V samples, scanning probe microscopy, X-ray photoelectron spectrometry (XPS), and contact angle tests were conducted to determine the surface topography, elemental composition and hydrophilicity, respectively. The change of surface morphology was further studied using sputtered titanium on silicon wafers. 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and F-actin immunofluorescence stain were performed to investigate the viability and spreading behavior of cultivated MG-63 cells on the samples. Results The surface roughness was most prominent after 5 min OPT in both CP-Ti and Ti6Al4V, and the surface morphology of sputtered Ti sharpened after the 5 min treatment. From the XPS results, the intensity of Ti°, Ti2+, and Ti3+ of the samples’ surface decreased indicating the oxidation of titanium after OPT. The water contact angles of both CP-Ti and Ti6Al4V were increased after 5 min OPT. The results of MTT assay demonstrated MG-63 cells proliferated best on the 5 min OP treated titanium sample. The F-actin immunofluorescence stain revealed the cultivated cell number of 5 min treated CP-Ti/Ti6Al4V was greater than other groups and most of the cultivated cells were spindle-shaped. Conclusions Low pressure RF oxygen plasma modified both the composition and the morphology of titanium samples’ surface. The CP-Ti/Ti6Al4V treated with 5 min

  13. The Role of Helium Metastable States in Radio-Frequency Helium-Oxygen Atmospheric Pressure Plasma Jets: Measurement and Numerical Simulation

    NASA Astrophysics Data System (ADS)

    Niemi, Kari; Waskoenig, Jochen; Sadeghi, Nader; Gans, Timo; O'Connell, Deborah

    2011-10-01

    Absolute densities of metastable He atoms were measured line-of sight integrated along the plasma channel of a capacitively-coupled radio-frequency driven atmospheric pressure plasma jet operated in helium oxygen mixtures by tunable diode-laser absorption spectroscopy. Dependencies of the He metastable density with oxygen admixtures up to 1 percent were investigated. Results are compared to a 1-d numerical simulation, which includes a semi-kinetical treatment of the electron dynamics and the complex plasma chemistry (20 species, 184 reactions), and very good agreement is found. The main formation mechanisms for the helium metastables are identified and analyzed, including their pronounced spatio-temporal dynamics. Penning ionization through helium metastables is found to be significant for plasma sustainment, while it is revealed that helium metastables are not an important energy carrying species into the jet effluent and therefore will not play a direct role in remote surface treatments.

  14. Radio Frequency Plasma in Water

    NASA Astrophysics Data System (ADS)

    Maehara, Tsunehiro; Toyota, Hiromichi; Kuramoto, Makoto; Iwamae, Atsushi; Tadokoro, Atsushi; Mukasa, Shinobu; Yamashita, Hiroshi; Kawashima, Ayato; Nomura, Shinfuku

    2006-11-01

    We generate a radio frequency (RF) plasma in water at an atmospheric pressure by applying an RF power of 13.56 MHz from an electrode. The plasma is in a bubble formed in water. On the basis of hydrogen spectral lines under the assumption of thermal equilibrium, the temperature of the plasma is estimated to be 4000-4500 K. Spectroscopic measurements show that hydrogen and oxygen are excited in the plasma. The plasma is also obtained in tap water or NaCl solution with a high conductivity. In the solution, sodium spectral lines are observed. Colored water containing methylene blue is exposed to the plasma. The absorbence spectra of the colored water before and after exposure to the plasma suggest the decomposition of organic matter due to chemical reactions involving active species, such as OH-radicals.

  15. Absolute atomic oxygen and nitrogen densities in radio-frequency driven atmospheric pressure cold plasmas: Synchrotron vacuum ultra-violet high-resolution Fourier-transform absorption measurements

    SciTech Connect

    Niemi, K.; O'Connell, D.; Gans, T.; Oliveira, N. de; Joyeux, D.; Nahon, L.; Booth, J. P.

    2013-07-15

    Reactive atomic species play a key role in emerging cold atmospheric pressure plasma applications, in particular, in plasma medicine. Absolute densities of atomic oxygen and atomic nitrogen were measured in a radio-frequency driven non-equilibrium plasma operated at atmospheric pressure using vacuum ultra-violet (VUV) absorption spectroscopy. The experiment was conducted on the DESIRS synchrotron beamline using a unique VUV Fourier-transform spectrometer. Measurements were carried out in plasmas operated in helium with air-like N{sub 2}/O{sub 2} (4:1) admixtures. A maximum in the O-atom concentration of (9.1 {+-} 0.7) Multiplication-Sign 10{sup 20} m{sup -3} was found at admixtures of 0.35 vol. %, while the N-atom concentration exhibits a maximum of (5.7 {+-} 0.4) Multiplication-Sign 10{sup 19} m{sup -3} at 0.1 vol. %.

  16. The role of helium metastable states in radio-frequency driven helium-oxygen atmospheric pressure plasma jets: measurement and numerical simulation

    NASA Astrophysics Data System (ADS)

    Niemi, K.; Waskoenig, J.; Sadeghi, N.; Gans, T.; O'Connell, D.

    2011-10-01

    Absolute densities of metastable He(23S1) atoms were measured line-of-sight integrated along the discharge channel of a capacitively coupled radio-frequency driven atmospheric pressure plasma jet operated in technologically relevant helium-oxygen mixtures by tunable diode-laser absorption spectroscopy. The dependences of the He(23S1) density in the homogeneous-glow-like α-mode plasma with oxygen admixtures up to 1% were investigated. The results are compared with a one-dimensional numerical simulation, which includes a semi-kinetical treatment of the pronounced electron dynamics and the complex plasma chemistry (in total 20 species and 184 reactions). Very good agreement between measurement and simulation is found. The main formation mechanisms for metastable helium atoms are identified and analyzed, including their pronounced spatio-temporal dynamics. Penning ionization through helium metastables is found to be significant for plasma sustainment, while it is revealed that helium metastables are not an important energy carrying species into the jet effluent and therefore will not play a direct role in remote surface treatments.

  17. On the E-H transition in inductively coupled radio frequency oxygen plasmas: II. Electronegativity and the impact on particle kinetics

    NASA Astrophysics Data System (ADS)

    Wegner, Th; Küllig, C.; Meichsner, J.

    2017-02-01

    In this series of two papers we present results about the E-H transition of an inductively coupled oxygen discharge driven at radio frequency (13.56 MHz) for different total gas pressures. The mode transition from the low density E-mode to the high density H-mode is studied using comprehensive plasma diagnostics. The measured electron density can be used to distinguish between the different operation modes. This paper focuses on the determination of the negative atomic ion density and the electronegativity by two experimental methods and global rate equation calculation. As a result, the electronegativity significantly decreases over two orders of magnitude from about 25 in the E-mode to about 0.1 in the H-mode. The temporal behavior of the electronegativity in pulsed ICP shows that the negative atomic ion density reaches a steady state after 10 ms. Negative atomic ions are mainly produced by the dissociative attachment with the molecular ground state. The ion-ion recombination with the positive molecular ions and the collisional detachment with the singlet molecular metastables contribute significantly to the loss of the negative atomic ions.

  18. A New Radio Frequency Plasma Oxygen Primary Ion Source on Nano Secondary Ion Mass Spectrometry for Improved Lateral Resolution and Detection of Electropositive Elements at Single Cell Level.

    PubMed

    Malherbe, Julien; Penen, Florent; Isaure, Marie-Pierre; Frank, Julia; Hause, Gerd; Dobritzsch, Dirk; Gontier, Etienne; Horréard, François; Hillion, François; Schaumlöffel, Dirk

    2016-07-19

    An important application field of secondary ion mass spectrometry at the nanometer scale (NanoSIMS) is the detection of chemical elements and, in particular, metals at the subcellular level in biological samples. The detection of many trace metals requires an oxygen primary ion source to allow the generation of positive secondary ions with high yield in the NanoSIMS. The duoplasmatron oxygen source is commonly used in this ion microprobe but cannot achieve the same quality of images as the cesium primary ion source used to produce negative secondary ions (C(-), CN(-), S(-), P(-)) due to a larger primary ion beam size. In this paper, a new type of an oxygen ion source using a rf plasma is fitted and characterized on a NanoSIMS50L. The performances of this primary ion source in terms of current density and achievable lateral resolution have been characterized and compared to the conventional duoplasmatron and cesium sources. The new rf plasma oxygen source offered a net improvement in terms of primary beam current density compared to the commonly used duoplasmatron source, which resulted in higher ultimate lateral resolutions down to 37 nm and which provided a 5-45 times higher apparent sensitivity for electropositive elements. Other advantages include a better long-term stability and reduced maintenance. This new rf plasma oxygen primary ion source has been applied to the localization of essential macroelements and trace metals at basal levels in two biological models, cells of Chlamydomonas reinhardtii and Arabidopsis thaliana.

  19. [Study of plasma temperature measurements for oxygen discharge].

    PubMed

    Li, Liu-Cheng; Wang, Zeng-Qiang; Li, Gu-Fu; Duo, Li-Ping

    2011-10-01

    A radio-frequency discharge setup was constructed by two shell-shaped copper electrodes and a 30 cm long pyrex glass tube (i. d. = 1.65 cm) to examine the gas temperature of oxygen plasma in electric discharge oxygen iodine laser. The discharge was supplied by a 500 watt, 13.56 MHz radio-frequency power. The gas pressure in the discharge cavity was 1 330 Pa. The temperature of oxygen discharge plasma was measured by using the P branch of O2 (b, v = 0) rotational emission spectrum. Two methods were used to deduce the oxygen gas temperature. They are Boltzman plotting method and computer simulating spectrum method, respectively. Gauss fitting method was used to distinguish spectrum peaks for lower resolution spectrum. The spectrum peak area was used to characterize the optical emission intensity. The gas temperature of oxygen discharge plasma was obtained by Boltzmann plotting method. Alternatively, the optical emission spectrum was simulated by computer modeling with spectrometer slit function which was obtained by He-Ne laser. Consequently, the gas temperature of oxygen plasma was obtained by comparing the computer simulating spectrum and the experimentally observed spectrum according to the least square fitting rule. The measurement results with the two methods agree well. It was concluded that the simple optical technique can be used conveniently in the temperature diagnostics of oxygen radio-frequency discharge plasma.

  20. Chamber For Testing Polymers In Oxygen Plasma

    NASA Technical Reports Server (NTRS)

    Whitaker, Ann F.

    1990-01-01

    Apparatus holds polymer specimen at constant temperature while exposing it to oxygen plasma. Copper tube (part of cooling coil) extends into plasma chamber, supporting copper block and thermoelectric module on which specimen mounted. Copper block made small - 4.4 by 3.8 by 1.6 cm - having little effect on plasma. Used to evaluate resistances of polymer materials to plasma environments, and for analysis of gases produced by attack of plasma on polymer specimen.

  1. Cleaning Carbon Nanotubes by Use of Mild Oxygen Plasmas

    NASA Technical Reports Server (NTRS)

    Petkov, Mihail

    2006-01-01

    Experiments have shown that it is feasible to use oxygen radicals (specifically, monatomic oxygen) from mild oxygen plasmas to remove organic contaminants and chemical fabrication residues from the surfaces of carbon nanotubes (CNTs) and metal/CNT interfaces. A capability for such cleaning is essential to the manufacture of reproducible CNT-based electronic devices. The use of oxygen radicals to clean surfaces of other materials is fairly well established. However, previously, cleaning of CNTs and of graphite by use of oxygen plasmas had not been attempted because both of these forms of carbon were known to be vulnerable to destruction by oxygen plasmas. The key to success of the present technique is, apparently, to ensure that the plasma is mild . that is to say, that the kinetic and internal energies of the oxygen radicals in the plasma are as low as possible. The plasma oxygen-radical source used in the experiments was a commercial one marketed for use in removing hydrocarbons and other organic contaminants from vacuum systems and from electron microscopes and other objects placed inside vacuum systems. In use, the source is installed in a vacuum system and air is leaked into the system at such a rate as to maintain a background pressure of .0.56 torr (.75 Pa). In the source, oxygen from the air is decomposed into monatomic oxygen by radio-frequency excitation of a resonance of the O2 molecule (N2 is not affected). Hence, what is produced is a mild (non-energetic) oxygen plasma. The oxygen radicals are transported along with the air molecules in the flow created by the vacuum pump. In the experiments, exposure to the oxygen plasma in this system was shown to remove organic contaminants and chemical fabrication residues from several specimens. Many high-magnification scanning electron microscope (SEM) images of CNTs were taken before and after exposure to the oxygen plasma. As in the example shown in the figure, none of these images showed evidence of degradation

  2. Biochar activated by oxygen plasma for supercapacitors

    NASA Astrophysics Data System (ADS)

    Gupta, Rakesh Kumar; Dubey, Mukul; Kharel, Parashu; Gu, Zhengrong; Fan, Qi Hua

    2015-01-01

    Biochar, also known as black carbon, is a byproduct of biomass pyrolysis. As a low-cost, environmental-friendly material, biochar has the potential to replace more expensive synthesized carbon nanomaterials (e.g. carbon nanotubes) for use in future supercapacitors. To achieve high capacitance, biochar requires proper activation. A conventional approach involves mixing biochar with a strong base and baking at a high temperature. However, this process is time consuming and energy inefficient (requiring temperatures >900 °C). This work demonstrates a low-temperature (<150 °C) plasma treatment that efficiently activates a yellow pine biochar. Particularly, the effects of oxygen plasma on the biochar microstructure and supercapacitor characteristics are studied. Significant enhancement of the capacitance is achieved: 171.4 F g-1 for a 5-min oxygen plasma activation, in comparison to 99.5 F g-1 for a conventional chemical activation and 60.4 F g-1 for untreated biochar. This enhancement of the charge storage capacity is attributed to the creation of a broad distribution in pore size and a larger surface area. The plasma activation mechanisms in terms of the evolution of the biochar surface and microstructure are further discussed.

  3. Atomic Oxygen Durability Evaluation of Protected Polymers Using Thermal Energy Plasma Systems

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Rutledge, Sharon K.; Degroh, Kim K.; Stidham, Curtis R.; Gebauer, Linda; Lamoreaux, Cynthia M.

    1995-01-01

    The durability evaluation of protected polymers intended for use in low Earth orbit (LEO) has necessitated the use of large-area, high-fluence, atomic oxygen exposure systems. Two thermal energy atomic oxygen exposure systems which are frequently used for such evaluations are radio frequency (RF) plasma ashers and electron cyclotron resonance plasma sources. Plasma source testing practices such as ample preparation, effective fluence prediction, atomic oxygen flux determination, erosion measurement, operational considerations, and erosion yield measurements are presented. Issues which influence the prediction of in-space durability based on ground laboratory thermal energy plasma system testing are also addressed.

  4. A low-energy linear oxygen plasma source

    SciTech Connect

    Anders, Andre; Yushkov, Georgy Yu.

    2007-01-08

    A new version of a Constricted Plasma Source is described,characterized by all metal-ceramic construction, a linear slit exit of180 mm length, and cw-operation (typically 50 kHz) at an average power of1.5 kW. The plasma source is here operated with oxygen gas, producingstreaming plasma that contains mainly positive molecular and atomic ions,and to a much lesser degree, negative ions. The maximum total ion currentobtained was about 0.5 A. The fraction of atomic ions reached more than10 percent of all ions when the flow rate was less then 10 sccm O2,corresponding to a chamber pressure of about 0.5 Pa for the selectedpumping speed. The energy distribution functions of the different ionspecies were measured with a combinedmass spectrometer and energyanalyzer. The time-averaged distribution functions were broad and rangedfrom about 30eV to 90 eV at 200 kHz and higher frequencies, while theywere only several eV broad at 50 kHz and lower frequencies, with themaximum located at about 40 eV for the grounded anode case. This maximumwas shifted down to about 7 eV when the anode was floating, indicatingthe important role of the plasma potential for the ion energy for a givensubstrate potential. The source could be scaled to greater length and maybe useful for functionalization of surfaces and plasma-assisteddeposition of compound films.

  5. High Frequency Plasma Generators for Ion Thrusters

    NASA Technical Reports Server (NTRS)

    Divergilio, W. F.; Goede, H.; Fosnight, V. V.

    1981-01-01

    The results of a one year program to experimentally adapt two new types of high frequency plasma generators to Argon ion thrusters and to analytically study a third high frequency source concept are presented. Conventional 30 cm two grid ion extraction was utilized or proposed for all three sources. The two plasma generating methods selected for experimental study were a radio frequency induction (RFI) source, operating at about 1 MHz, and an electron cyclotron heated (ECH) plasma source operating at about 5 GHz. Both sources utilize multi-linecusp permanent magnet configurations for plasma confinement. The plasma characteristics, plasma loading of the rf antenna, and the rf frequency dependence of source efficiency and antenna circuit efficiency are described for the RFI Multi-cusp source. In a series of tests of this source at Lewis Research Center, minimum discharge losses of 220+/-10 eV/ion were obtained with propellant utilization of .45 at a beam current of 3 amperes. Possible improvement modifications are discussed.

  6. High-frequency underwater plasma discharge application in antibacterial activity

    NASA Astrophysics Data System (ADS)

    Ahmed, M. W.; Choi, S.; Lyakhov, K.; Shaislamov, U.; Mongre, R. K.; Jeong, D. K.; Suresh, R.; Lee, H. J.

    2017-03-01

    Plasma discharge is a novel disinfection and effectual inactivation approach to treat microorganisms in aqueous systems. Inactivation of Gram-negative Escherichia coli (E. coli) by generating high-frequency, high-voltage, oxygen (O2) injected and hydrogen peroxide (H2O2) added discharge in water was achieved. The effect of H2O2 dose and oxygen injection rate on electrical characteristics of discharge and E. coli disinfection has been reported. Microbial log reduction dependent on H2O2 addition with O2 injection was observed. The time variation of the inactivation efficiency quantified by the log reduction of the initial E. coli population on the basis of optical density measurement was reported. The analysis of emission spectrum recorded after discharge occurrence illustrated the formation of oxidant species (OH•, H, and O). Interestingly, the results demonstrated that O2 injected and H2O2 added, underwater plasma discharge had fabulous impact on the E. coli sterilization. The oxygen injection notably reduced the voltage needed for generating breakdown in flowing water and escalated the power of discharge pulses. No impact of hydrogen peroxide addition on breakdown voltage was observed. A significant role of oxidant species in bacterial inactivation also has been identified. Furthermore the E. coli survivability in plasma treated water with oxygen injection and hydrogen peroxide addition drastically reduced to zero. The time course study also showed that the retardant effect on E. coli colony multiplication in plasma treated water was favorable, observed after long time. High-frequency underwater plasma discharge based biological applications is technically relevant and would act as baseline data for the development of novel antibacterial processing strategies.

  7. High frequency plasma generator for ion thrusters

    NASA Technical Reports Server (NTRS)

    Goede, H.; Divergilio, W. F.; Fosnight, V. V.; Komatsu, G.

    1984-01-01

    The results of a program to experimentally develop two new types of plasma generators for 30 cm electrostatic argon ion thrusters are presented. The two plasma generating methods selected for this study were by radio frequency induction (RFI), operating at an input power frequency of 1 MHz, and by electron cyclotron heating (ECH) at an operating frequency of 5.0 GHz. Both of these generators utilize multiline cusp permanent magnet configurations for plasma confinement and beam profile optimization. The program goals were to develop a plasma generator possessing the characteristics of high electrical efficiency (low eV/ion) and simplicity of operation while maintaining the reliability and durability of the conventional hollow cathode plasma sources. The RFI plasma generator has achieved minimum discharge losses of 120 eV/ion while the ECH generator has obtained 145 eV/ion, assuming a 90% ion optical transparency of the electrostatic acceleration system. Details of experimental tests with a variety of magnet configurations are presented.

  8. Low-Frequency Waves in Space Plasmas

    NASA Astrophysics Data System (ADS)

    Keiling, Andreas; Lee, Dong-Hun; Nakariakov, Valery

    2016-02-01

    Low-frequency waves in space plasmas have been studied for several decades, and our knowledge gain has been incremental with several paradigm-changing leaps forward. In our solar system, such waves occur in the ionospheres and magnetospheres of planets, and around our Moon. They occur in the solar wind, and more recently, they have been confirmed in the Sun's atmosphere as well. The goal of wave research is to understand their generation, their propagation, and their interaction with the surrounding plasma. Low-frequency Waves in Space Plasmas presents a concise and authoritative up-to-date look on where wave research stands: What have we learned in the last decade? What are unanswered questions? While in the past waves in different astrophysical plasmas have been largely treated in separate books, the unique feature of this monograph is that it covers waves in many plasma regions, including: Waves in geospace, including ionosphere and magnetosphere Waves in planetary magnetospheres Waves at the Moon Waves in the solar wind Waves in the solar atmosphere Because of the breadth of topics covered, this volume should appeal to a broad community of space scientists and students, and it should also be of interest to astronomers/astrophysicists who are studying space plasmas beyond our Solar System.

  9. Replacement of hydrogen peroxide cleaning with oxygen plasma

    NASA Astrophysics Data System (ADS)

    Adams, B. E.

    1992-03-01

    Comparison between the standard peroxide cleaning method and an oxygen plasma modified version was run on thin film bond monitors. The plasma modified version substituted oxygen plasma for the peroxide cleaning step in the process and reduced the DI rinse water temperature from 75 C to 25 C. A direct surface cleanliness comparison was made between the two cleaning methods using Auger spectroscopy. A beam lead and ribbon bonding experiment was also run on plasma-cleaned networks. Results of both experiments indicate that plasma cleaning is superior to peroxide cleaning and that reliable bonding can be done on plasma-cleaned thin film networks.

  10. Time evolution of low frequency plasma modes

    NASA Astrophysics Data System (ADS)

    Gratton, Fausto T.; Gnavi, Graciela; Biernat, Helfried K.; Heyn, Martin F.; Rijnbeek, Richard P.

    The time evolution of linear, low frequency, plasma waves in the emission region is studied via theoretical properties and numerical solutions of Volterra integral equations of the second kind. Bounds for the growth rates of unstable plasmas, with arbitrary distribution functions, are established. The asymptotic value of the electric field E(infinity) is found by means of the Paley-Wiener theorem for stable plasmas. For initial perturbations of the distribution function f1(0) which are square integrable, E(infinity) = 0 (Landau damping). When f1(0) contains beams of particles (it is not square integrable) E(infinity) does not equal O. The arbitrariness of the time decay of the electric field is obtained straightforwardly. Some examples of numerical solutions for electron plasma waves and electron Bernstein modes are given.

  11. New oxygen plasma process rivals laser cutting methods

    SciTech Connect

    Fernicola, R.C. )

    1994-06-01

    For many years, oxygen plasma cutting has been looked upon as a desirable process for cutting steel but not practical in production because of very short consumable parts life. Recently, a number of technical advances in the oxygen plasma cutting process provides parts life several times that of older systems and cut quality approaching that of laser systems. This paper discusses these advances.

  12. High-frequency plasma-heating apparatus

    DOEpatents

    Brambilla, Marco; Lallia, Pascal

    1978-01-01

    An array of adjacent wave guides feed high-frequency energy into a vacuum chamber in which a toroidal plasma is confined by a magnetic field, the wave guide array being located between two toroidal current windings. Waves are excited in the wave guide at a frequency substantially equal to the lower frequency hybrid wave of the plasma and a substantially equal phase shift is provided from one guide to the next between the waves therein. For plasmas of low peripheral density gradient, the guides are excited in the TE.sub.01 mode and the output electric field is parallel to the direction of the toroidal magnetic field. For exciting waves in plasmas of high peripheral density gradient, the guides are excited in the TM.sub.01 mode and the magnetic field at the wave guide outlets is parallel to the direction of the toroidal magnetic field. The wave excited at the outlet of the wave guide array is a progressive wave propagating in the direction opposite to that of the toroidal current and is, therefore, not absorbed by so-called "runaway" electrons.

  13. Analysis of blood plasma at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Cherkasova, O. P.; Nazarov, M. M.; Angeluts, A. A.; Shkurinov, A. P.

    2016-01-01

    Terahertz time-domain spectroscopy in the 0.05-2.5 THz frequency range was employed to analyze blood plasma samples obtained from laboratory animals with experimental diabetes and from healthy controls. It was found that transmission and reflection coefficients of samples from rats with diabetes differed significantly from control values in both amplitude and phase. The cause of the detected differences is discussed with respect to variation in the terahertz response of water.

  14. How plasma induced oxidation, oxygenation, and de-oxygenation influences viability of skin cells

    NASA Astrophysics Data System (ADS)

    Oh, Jun-Seok; Strudwick, Xanthe; Short, Robert D.; Ogawa, Kotaro; Hatta, Akimitsu; Furuta, Hiroshi; Gaur, Nishtha; Hong, Sung-Ha; Cowin, Allison J.; Fukuhara, Hideo; Inoue, Keiji; Ito, Masafumi; Charles, Christine; Boswell, Roderick W.; Bradley, James W.; Graves, David B.; Szili, Endre J.

    2016-11-01

    The effect of oxidation, oxygenation, and de-oxygenation arising from He gas jet and He plasma jet treatments on the viability of skin cells cultured in vitro has been investigated. He gas jet treatment de-oxygenated cell culture medium in a process referred to as "sparging." He plasma jet treatments oxidized, as well as oxygenated or de-oxygenated cell culture medium depending on the dissolved oxygen concentration at the time of treatment. He gas and plasma jets were shown to have beneficial or deleterious effects on skin cells depending on the concentration of dissolved oxygen and other oxidative molecules at the time of treatment. Different combinations of treatments with He gas and plasma jets can be used to modulate the concentrations of dissolved oxygen and other oxidative molecules to influence cell viability. This study highlights the importance of a priori knowledge of the concentration of dissolved oxygen at the time of plasma jet treatment, given the potential for significant impact on the biological or medical outcome. Monitoring and controlling the dynamic changes in dissolved oxygen is essential in order to develop effective strategies for the use of cold atmospheric plasma jets in biology and medicine.

  15. Plasma processing of superconducting radio frequency cavities

    NASA Astrophysics Data System (ADS)

    Upadhyay, Janardan

    The development of plasma processing technology of superconducting radio frequency (SRF) cavities not only provides a chemical free and less expensive processing method, but also opens up the possibility for controlled modification of the inner surfaces of the cavity for better superconducting properties. The research was focused on the transition of plasma etching from two dimensional flat surfaces to inner surfaces of three dimensional (3D) structures. The results could be applicable to a variety of inner surfaces of 3D structures other than SRF cavities. Understanding the Ar/Cl2 plasma etching mechanism is crucial for achieving the desired modification of Nb SRF cavities. In the process of developing plasma etching technology, an apparatus was built and a method was developed to plasma etch a single cell Pill Box cavity. The plasma characterization was done with the help of optical emission spectroscopy. The Nb etch rate at various points of this cavity was measured before processing the SRF cavity. Cylindrical ring-type samples of Nb placed on the inner surface of the outer wall were used to measure the dependence of the process parameters on plasma etching. The measured etch rate dependence on the pressure, rf power, dc bias, temperature, Cl2 concentration and diameter of the inner electrode was determined. The etch rate mechanism was studied by varying the temperature of the outer wall, the dc bias on the inner electrode and gas conditions. In a coaxial plasma reactor, uniform plasma etching along the cylindrical structure is a challenging task due to depletion of the active radicals along the gas flow direction. The dependence of etch rate uniformity along the cylindrical axis was determined as a function of process parameters. The formation of dc self-biases due to surface area asymmetry in this type of plasma and its variation on the pressure, rf power and gas composition was measured. Enhancing the surface area of the inner electrode to reduce the

  16. Cold atmospheric pressure plasma jets as sources of singlet delta oxygen for biomedical applications

    SciTech Connect

    Sousa, J. S.; Niemi, K.; Cox, L. J.; Algwari, Q. Th.; Gans, T.; O'Connell, D.

    2011-06-15

    Absolute densities of singlet delta oxygen (SDO) molecules were measured using infrared optical emission spectroscopy in the flowing effluents of two different atmospheric-pressure plasma jets (APPJs): a capacitively coupled radio-frequency-driven jet (rf-APPJ) and a lower frequency kilohertz-driven dielectric barrier discharge jet. The plasma jets were operated in helium, with small admixtures of molecular oxygen (O{sub 2} < 2%). High absolute SDO densities of up to 6.2 x 10{sup 15} cm{sup -3} were measured at approximately 10 cm downstream. The rf-APPJ seems to be much more efficient in producing SDO. The influence of different parameters, such as gas flows and mixtures and power coupled to the plasmas, on the production of SDO by the two APPJs has been investigated. Despite the considerable differences between the two plasma jets (excitation frequency, electric field direction, inter-electrode distance, plasma propagation), similar dependencies on the oxygen admixture and on the dissipated power were found in both APPJs. However, opposite trends were observed for the gas flow dependence. The results presented in this paper show that the control of the external operating conditions of each APPJ enables the tailoring of the SDO composition of both plasma effluents. This provides scope to tune the plasma jets for desired applications, e.g., in biomedicine.

  17. Oxygen plasma-treatment effects on Si transfer.

    PubMed

    Langowski, Bryan A; Uhrich, Kathryn E

    2005-07-05

    Oxygen plasma-treatment is commonly used to increase the hydrophilicity of poly(dimethylsiloxane) (PDMS) stamps used for microcontact printing (muCP) aqueous-based inks. Review of the literature reveals that a wide range of plasma parameters are currently employed to modify stamp surfaces. However, little is known about the effect of these parameters (e.g., power, chamber pressure, duration) on the undesirable transfer of low-molecular-weight silicon-containing fragments from the stamps that commonly occurs during muCP. To study the effect of oxygen plasma-treatment on Si transfer, unpatterned PDMS stamps were treated with oxygen plasma under various conditions and used to stamp deionized water on plasma-activated poly(methyl methacrylate) (PMMA) substrates. Once stamped, the PMMA substrates were analyzed with X-ray photoelectron spectroscopy (XPS) to quantify and characterize silicon present on the substrate surface. In addition, used PDMS stamps were analyzed with scanning electron microscopy (SEM) to observe topographical changes that occur during oxygen plasma-treatment. XPS results show that all plasma treatments studied significantly reduced the amount of Si transfer from the treated stamps during muCP as compared to untreated PDMS stamps and that the source of transfer is residual PDMS fragments not removed by oxygen plasma. SEM results show that, although the treated stamps undergo a variety of topographical changes, no correlation exists between stamp topography and extent of Si transfer from the stamps.

  18. Growth Enhancement of Radish Sprouts Induced by Low Pressure O2 Radio Frequency Discharge Plasma Irradiation

    NASA Astrophysics Data System (ADS)

    Kitazaki, Satoshi; Koga, Kazunori; Shiratani, Masaharu; Hayashi, Nobuya

    2012-01-01

    We studied growth enhancement of radish sprouts (Raphanus sativus L.) induced by low pressure O2 radio frequency (RF) discharge plasma irradiation. The average length of radish sprouts cultivated for 7 days after O2 plasma irradiation is 30-60% greater than that without irradiation. O2 plasma irradiation does not affect seed germination. The experimental results reveal that oxygen related radicals strongly enhance growth, whereas ions and photons do not.

  19. Long-distance oxygen plasma sterilization: Effects and mechanisms

    NASA Astrophysics Data System (ADS)

    Liu, Hongxia; Chen, Jierong; Yang, Liqing; Zhou, Yuan

    2008-01-01

    The distribution of electrons, ions and oxygen radicals in long-distance oxygen plasma and the germicidal effect (GE) of Escherichia coli on the surface of medical poly(tetrafluoroethylene) (PTFE) film were studied. The quantity of protein leakage and the production of lipid peroxide in bacterial suspension as well as the state of DNA were measured after sterilization to analyse the inactivation mechanisms. The results showed that the concentration of electrons and ions decreased rapidly with increasing the distance from the center of induction coil, which approximated to 0 at 30 cm, whereas the concentration of oxygen radicals reduced slowly, i.e. decreased 30% within 40 cm. GE value reached 3.42 in the active discharge zone (0 cm) and exceeded 3.32 within 40 cm when plasma treatment parameters were set as follows: plasma rf power at 100 W, treatment time at 60 s and oxygen flux at 40 cm 3/min. Fast etching action on cell membrane by electrons, ions and attacking polyunsaturation fatty acid (PUFA) in cell membrane by oxygen radicals are primary reasons of oxygen plasma sterilization in the active discharge and the afterglow zone, respectively. The GE of UV radiation in long-distance oxygen plasma is feebleness.

  20. Radio Frequency Plasma Applications for Space Propulsion

    SciTech Connect

    Baity, F.W., Jr.; Barber, G.C.; Carter, M.D.; Chang-Diaz, F.R.; Goulding, R.H.; Ilin, A.V.; Jaeger, E.F.; Sparks, D.O.; Squire, J.P.

    1999-09-13

    Recent developments in solid-state radio frequency (RF) power technologies allow for the practical consideration of RF heated plasmas for space propulsion. These technologies permit the use of any electrical power source, de-couple the power and propellant sources, and allow for the effcient use of both the propellant mass and power. Effcient use of the propellant is obtained by expelling the rocket exhaust at the highest possible velocity, which can be orders of magnitude higher than those achieved in chemical rockets. Handling the hot plasma exhaust requires the use of magnetic nozzles, and the basic physics of ion detachment from the magnetic eld is discussed. The plasma can be generated by RF using helicon waves to heat electrons. Further direct heating of the ions helps to reduce the line radiation losses, and the magnetic geometry is tailored to allow ion cyclotron resonance heating. RF eld and ion trajectory calculations are presented to give a reasonably self-consistent picture of the ion acceleration process.

  1. FREQUENCY CONTROL OF RF HEATING OF GASEOUS PLASMA

    DOEpatents

    Herold, E.W.

    1962-09-01

    This invention relates to the heating of gaseous plasma by radiofrequency ion-cyclotron resonance heating. The cyclotron resonance frequencies are varied and this invention provides means for automatically controlling the frequency of the radiofrequency to maximize the rate of heating. To this end, a servo-loop is provided to sense the direction of plasma heating with frequency and a control signal is derived to set the center frequency of the radiofrequency energy employed to heat the plasma. (AEC)

  2. Modification of the Surface Properties of Polyimide Films using POSS Deposition and Oxygen Plasma Exposure

    NASA Technical Reports Server (NTRS)

    Wohl, Christopher J.; Belcher, Marcus A.; Ghose, Sayata; Connell, John W.

    2008-01-01

    Topographically rich surfaces were generated by spray-coating organic solutions of a polyhedral oligomeric silsesquioxane, octakis (dimethylsilyloxy) silsesquioxane (POSS), on Kapton HN films and exposing them to radio frequency generated oxygen plasma. Changes in both surface chemistry and topography were observed. High-resolution scanning electron microscopy indicated substantial modification of the POSS-coated polyimide surface topographies as a result of oxygen plasma exposure. Water contact angles varied from 104 deg for unexposed POSS-coated surfaces to approximately 5 deg, for samples exposed for 5 h. Modulation of the dispersive and polar contributions to the surface energy was determined using van Oss Good Chaudhury theory.

  3. Oxygen plasmas used to synthesize superoxides

    NASA Technical Reports Server (NTRS)

    Hollahan, J. R.; Wydeven, T.

    1972-01-01

    Production of alkali metal superoxides by interaction of molecular oxygen with alkali metals or their salts is discussed. Diagram of reactor to show components and operating principles is provided. Analysis of chemical reactions involved is developed.

  4. Atomic oxygen patterning from a biomedical needle-plasma source

    SciTech Connect

    Kelly, Seán; Turner, Miles M.

    2013-09-28

    A “plasma needle” is a cold plasma source operating at atmospheric pressure. Such sources interact strongly with living cells, but experimental studies on bacterial samples show that this interaction has a surprising pattern resulting in circular or annular killing structures. This paper presents numerical simulations showing that this pattern occurs because biologically active reactive oxygen and nitrogen species are produced dominantly where effluent from the plasma needle interacts with ambient air. A novel solution strategy is utilised coupling plasma produced neutral (uncharged) reactive species to the gas dynamics solving for steady state profiles at the treated biological surface. Numerical results are compared with experimental reports corroborating evidence for atomic oxygen as a key bactericidal species. Surface losses are considered for interaction of plasma produced reactants with reactive solid and liquid interfaces. Atomic oxygen surface reactions on a reactive solid surface with adsorption probabilities above 0.1 are shown to be limited by the flux of atomic oxygen from the plasma. Interaction of the source with an aqueous surface showed hydrogen peroxide as the dominant species at this interface.

  5. Sintering of alumina in microwave-induced oxygen plasma

    SciTech Connect

    Su, H.; Johnson, D.L.

    1996-12-01

    Small cylindrical tubes were sintered in a microwave-induced oxygen plasma, initiated and sustained inside a tunable, single-mode cavity. Temperature and shrinkage measurements of the specimens were achieved using an optical-fiber thermometer black-body sensor and a dilatometer, respectively. Sintering experiments at constant heating rate were accomplished to obtain the activation energy for sintering of alumina in the plasma and in a conventional rapid-heating furnace. Diffusion of aluminum interstitials along grain boundaries was believed to be the dominant sintering mechanism, with an estimated activation energy of 488 {+-} 20 kJ/mol for conventional sintering and an average activation energy of 468 {+-} 20 kJ/mol for plasma sintering. A comparison of specimens sintered in the plasma to those sintered in a conventional furnace under the same temperature-time excursions and oxygen pressures showed an athermal effect due to the plasma. To further explore this athermal effect, sintering experiments in plasmas of different oxygen pressure were conducted. The athermal effect was ascribed to an increase of aluminum interstitial concentration during plasma sintering. Sintering data were interpreted using the combined-stage sintering model.

  6. Material Compatibility of Medical Sterilizer Using Oxygen Plasma

    NASA Astrophysics Data System (ADS)

    Tanaka, Hiroshi; Ono, Reoto; Hayashi, Nobuya; Hanada, Yasushi; Noda, Minoru; Goto, Masaaki

    2015-09-01

    Material compatibility of oxygen plasma sterilizer is investigated comparing with hydrogen peroxide (H2O2) sterilizers and a gaseous H2O2 sterilizer. Organic materials such as ABS, PE, PP, and PET are used as sample materials, and are irradiated by active oxygen species produced in oxygen plasma. After plasma irradiation, surface of the sample materials is observed using a scanning electron microscope and FTIR spectroscopy. Strengths of the organic materials are evaluated by the tension test. Also, H2O2 plasma sterilizer and a gaseous H2O2 sterilizer those are commercially available are utilized to compare the material compatibility, especially organic compounds. The ABS resin becomes slightly soft after irradiation by both plasmas and gaseous H2O2. Also, PET material becomes soften by each sterilization treatment. Decrease of peak heights of CH around 1200 and 1730 cm-1 and increase of that of OH at 3300 cm-1 in FTIR spectra indicates the oxidation of ABS resin by both plasma and gaseous H2O2. In the case of PET material, treatment by the plasma has not modified chemical composition but changed the crystal structure. The gaseous H2O2 is completely friendly for the PET material.

  7. Electron-vibration relaxation in oxygen plasmas

    NASA Astrophysics Data System (ADS)

    Laporta, V.; Heritier, K. L.; Panesi, M.

    2016-06-01

    An ideal chemical reactor model is used to study the vibrational relaxation of oxygen molecules in their ground electronic state, X3Σg-, in presence of free electrons. The model accounts for vibrational non-equilibrium between the translational energy mode of the gas and the vibrational energy mode of individual molecules. The vibrational levels of the molecules are treated as separate species, allowing for non-Boltzmann distributions of their population. The electron and vibrational temperatures are varied in the range [0-20,000] K. Numerical results show a fast energy transfer between oxygen molecules and free electron, which causes strong deviation of the vibrational distribution function from Boltzmann distribution, both in heating and cooling conditions. Comparison with Landau-Teller model is considered showing a good agreement for electron temperature range [2000-12,000] K. Finally analytical fit of the vibrational relaxation time is given.

  8. Tailoring surface properties of polyethylene separator by low pressure 13.56 MHz RF oxygen plasma glow discharge

    NASA Astrophysics Data System (ADS)

    Li, Chun; Liang, Chia-Han; Huang, Chun

    2016-01-01

    Low-pressure plasma surface modification in a radio-frequency capacitively coupled glow discharge of oxygen gas was carried out to induce polar functional groups onto polyethylene membrane separator surfaces to enhance its hydrophilicity. The surface changes in surface free energy were monitored by static contact angle measurement. A significant increase in the surface energy of polyethylene membrane separators caused by the oxygen gas plasma modifications was observed. The static water contact angle of the plasma-modified membrane separator significantly decreased with the increase in treatment duration and plasma power. An obvious increase in the surface energy of the membrane separators owing to the oxidative effect of oxygen-gas-plasma modifications was also observed. Optical emission spectroscopy was carried out to analyze the chemical species generated by oxygen gas plasma surface modification. The variations in the surface morphology and chemical structure of the separators were confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). XPS showed significantly higher surface concentrations of oxygen functional groups in the oxygen-gas-plasma-modified polymeric separator surfaces than in the unmodified polymeric separator surface. The experimental results show the important role of chemical species in the interaction between oxygen gas plasmas and the separator surface, which can be controlled by surface modification to tailor the hydrophilicity of the separator.

  9. Oxygen impurity radiation from Tokamak-like plasmas

    NASA Technical Reports Server (NTRS)

    Rogerson, J. E.; Davis, J.; Jacobs, V. L.

    1977-01-01

    We have constructed a nonhydrodynamic coronal model for calculating radiation from impurity atoms in a heated plasma. Some recent developments in the calculation of dielectronic recombination rate coefficients and collisional excitation rate coefficients are included. The model is applied to oxygen impurity radiation during the first few milliseconds of a TFR Tokamak plasma discharge, and good agreement with experimental results is obtained. Estimates of total line and continuum radiation from the oxygen impurity are given. It is shown that impurity radiation represents a considerable energy loss.

  10. Fluorophore-based sensor for oxygen radicals in processing plasmas

    SciTech Connect

    Choudhury, Faraz A.; Shohet, J. Leon; Sabat, Grzegorz; Sussman, Michael R.; Nishi, Yoshio

    2015-11-15

    A high concentration of radicals is present in many processing plasmas, which affects the processing conditions and the properties of materials exposed to the plasma. Determining the types and concentrations of free radicals present in the plasma is critical in order to determine their effects on the materials being processed. Current methods for detecting free radicals in a plasma require multiple expensive and bulky instruments, complex setups, and often, modifications to the plasma reactor. This work presents a simple technique that detects reactive-oxygen radicals incident on a surface from a plasma. The measurements are made using a fluorophore dye that is commonly used in biological and cellular systems for assay labeling in liquids. Using fluorometric analysis, it was found that the fluorophore reacts with oxygen radicals incident from the plasma, which is indicated by degradation of its fluorescence. As plasma power was increased, the quenching of the fluorescence significantly increased. Both immobilized and nonimmobilized fluorophore dyes were used and the results indicate that both states function effectively under vacuum conditions. The reaction mechanism is very similar to that of the liquid dye.

  11. Dual radio frequency plasma source: Understanding via electrical asymmetry effect

    SciTech Connect

    Bora, B.; Bhuyan, H.; Favre, M.; Wyndham, E.; Wong, C. S.

    2013-04-21

    On the basis of the global model, the influences of driving voltage and frequency on electron heating in geometrically symmetrical dual capacitively coupled radio frequency plasma have been investigated. Consistent with the experimental and simulation results, non-monotonic behavior of dc self bias and plasma heating with increasing high frequency is observed. In addition to the local maxima of plasma parameters for the integer values of the ratio between the frequencies ({xi}), ourstudies also predict local maxima for odd integer values of 2{xi} as a consequence of the electrical asymmetry effect produced by dual frequency voltage sources.

  12. Low-frequency fluctuations in plasma magnetic fields

    NASA Astrophysics Data System (ADS)

    Cable, S.; Tajima, T.

    1992-02-01

    It is shown that even a non-magnetized plasma with temperature T sustains zero-frequency magnetic fluctuations in thermal equilibrium. Fluctuations in electric and magnetic fields, as well as in densities, are computed. Four cases are studied: a cold, gaseous, isotropic, non-magnetized plasma; a cold, gaseous plasma in a uniform magnetic field; a warm, gaseous plasma described by kinetic theory; and a degenerate electron plasma. For the simple gaseous plasma, the fluctuation strength of the magnetic field as a function of frequency and wavenumber is calculated with the aid of the fluctuation-dissipation theorem. This calculation is done for both collisional and collisionless plasmas. The magnetic field fluctuation spectrum of each plasma has a large zero-frequency peak. The peak is a Dirac delta function in the collisionless plasma and is broadened into a Lorentzian curve in the collisional plasma. The plasma causes a low frequency cutoff in the typical black-body radiation spectrum, and the energy under the discovered peak approximates the energy lost in this cutoff. When the imposed magnetic field is weak, the magnetic field wave vector fluctuation spectra of the two lowest modes are independent of the strength of the imposed field. Further, these modes contain finite energy even when the imposed field is zero. It is the energy of these modes which forms the non-magnetized zero-frequency peak of the isotropic plasma. In deriving these results, a simple relationship between the dispersion relation and the fluctuation power spectrum of electromagnetic waves if found. The warm plasma is shown, by kinetic theory, to exhibit a zero-frequency peak in its magnetic field fluctuation spectrum as well. For the degenerate plasma, we find that electric field fluctuations and number density fluctuations vanish at zero frequency; however, the magnetic field power spectrum diverges at zero frequency.

  13. Surface energy increase of oxygen-plasma-treated PET

    SciTech Connect

    Cioffi, M.O.H.; Voorwald, H.J.C.; Mota, R.P

    2003-03-15

    Prosthetic composite is a widely used biomaterial that satisfies the criteria for application as an organic implant without adverse reactions. Polyethylene therephthalate (PET) fiber-reinforced composites have been used because of the excellent cell adhesion, biodegradability and biocompatibility. The chemical inertness and low surface energy of PET in general are associated with inadequate bonds for polymer reinforcements. It is recognized that the high strength of composites, which results from the interaction between the constituents, is directly related to the interfacial condition or to the interphase. A radio frequency plasma reactor using oxygen was used to treat PET fibers for 5, 20, 30 and 100 s. The treatment conditions were 13.56 MHz, 50 W, 40 Pa and 3.33x10{sup -7} m{sup 3}/s. A Rame-Hart goniometer was used to measure the contact angle and surface energy variation of fibers treated for different times. The experimental results showed contact angle values from 47 deg. to 13 deg. and surface energies from 6.4x10{sup -6} to 8.3x10{sup -6} J for the range of 5 to 100 s, respectively. These results were confirmed by the average ultimate tensile strength of the PET fiber/ polymethylmethacrylate (PMMA) matrix composite tested in tensile mode and by scanning electron microscopy.

  14. Calculation of the Lattice Frequencies of Alpha and Beta Oxygen.

    DTIC Science & Technology

    The optically active lattice frequencies of alpha- and beta-O2 have been calculated using an atom-atom Lennard - Jones potential, with and without the...agreement is obtained between the observed librational frequency and its temperature dependence in beta-O2 and the results calculated using the Lennard - Jones potential... Lennard - Jones atom-atom interaction is a satisfactory model for the potential function in solid oxygen, provided that the packing is such that electronic overlap effects are small. (Author)

  15. Spontaneous emission near the electron plasma frequency in a plasma with a runaway electron tail

    NASA Technical Reports Server (NTRS)

    Freund, H. P.; Lee, L. C.; Wu, C. S.

    1978-01-01

    Spontaneous emission of radiation with frequencies near the electron plasma frequency is studied for a plasma which consists of both thermal and runaway electrons. It is found that a substantial enhancement of the spontaneous radiation intensity can occur in this frequency regime via a Cherenkov resonance with the runaway electrons. Numerical analysis indicates that, for reasonable estimates of densities and energies, the plasma-frequency radiation can attain levels greater than the peak thermal emission at the second gyroharmonic.

  16. Plasma effects on the generation of reactive oxygen and nitrogen species in cancer cells in-vitro exposed by atmospheric pressure pulsed plasma jets

    NASA Astrophysics Data System (ADS)

    Kim, Sun Ja; Chung, T. H.

    2015-08-01

    Atmospheric pressure pulsed helium plasma jets are utilized for plasma-cell interactions. The effect of operating parameters such as applied voltage, pulse repetition frequency, and duty ratio on the generation of specific reactive oxygen and nitrogen species in gas and liquid phases and within cells is investigated. The apoptotic changes detected by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling assay in cells caused by plasma exposure are observed to correlate well with the levels of extracellular and intracellular reactive oxygen and nitrogen species.

  17. High-frequency Probing Diagnostic for Hall Current Plasma Thrusters

    SciTech Connect

    A.A. Litvak; Y. Raitses; N.J. Fisch

    2001-10-25

    High-frequency oscillations (1-100 MHz) in Hall thrusters have apparently eluded significant experimental scrutiny. A diagnostic setup, consisting of a single Langmuir probe, a special shielded probe connector-positioner, and an electronic impedance-matching circuit, was successfully built and calibrated. Through simultaneous high-frequency probing of the Hall thruster plasma at multiple locations, high-frequency plasma waves have been identified and characterized for various thruster operating conditions.

  18. Band gap effects of hexagonal boron nitride using oxygen plasma

    SciTech Connect

    Sevak Singh, Ram; Leong Chow, Wai; Yingjie Tay, Roland; Hon Tsang, Siu; Mallick, Govind; Tong Teo, Edwin Hang

    2014-04-21

    Tuning of band gap of hexagonal boron nitride (h-BN) has been a challenging problem due to its inherent chemical stability and inertness. In this work, we report the changes in band gaps in a few layers of chemical vapor deposition processed as-grown h-BN using a simple oxygen plasma treatment. Optical absorption spectra show a trend of band gap narrowing monotonically from 6 eV of pristine h-BN to 4.31 eV when exposed to oxygen plasma for 12 s. The narrowing of band gap causes the reduction in electrical resistance by ∼100 fold. The x-ray photoelectron spectroscopy results of plasma treated hexagonal boron nitride surface show the predominant doping of oxygen for the nitrogen vacancy. Energy sub-band formations inside the band gap of h-BN, due to the incorporation of oxygen dopants, cause a red shift in absorption edge corresponding to the band gap narrowing.

  19. Experimental investigations of driving frequency effect in low-pressure capacitively coupled oxygen discharges

    SciTech Connect

    Liu, Jia; Liu, Yong-Xin; Liu, Gang-Hu; Gao, Fei; Wang, You-Nian

    2015-04-14

    The effect of driving frequency on the electron density is investigated in low-pressure capacitively coupled oxygen plasmas by utilizing a floating hairpin probe. The power absorbed by the plasma is investigated and it is found that the power lost in the matching network can reach 50% or higher under certain conditions. The effect of driving frequency on the electron density is studied from two aspects, i.e., constant absorbed power and electrode voltage. In the former case, the electron density increases with the driving frequency increasing from 13.56 to 40.68 MHz and slightly changes depending on the gas pressures with the frequency further increasing to 100 MHz. In the latter case, the electron density rapidly increases when the driving frequency increases from 13.56 to 40.68 MHz, and then decreases with the frequency further increasing to 100 MHz. The electron series resonance is observed at 40.68 MHz and can be attributed to the higher electron density. And the standing wave effect also plays an important role in increasing electron density at 100 MHz and 2.6 Pa.

  20. Measurements of the Plasma Parameters and Low Frequency Oscillations in the Fisk Plasma Source

    NASA Technical Reports Server (NTRS)

    Thomas, Edward, Jr.; Wallace, Kent; Lampkin, Gregory; Watson, Michael

    1998-01-01

    A new plasma device, the Fisk Plasma Source (FPS), has been developed at Fisk University. This plasma device is used to study the physics of low temperature plasmas and plasma-material interactions. The FPS device is a stainless steel vacuum 6-way cross vacuum vessel with at 10-inch inner diameter. Low temperature argon plasmas are generated using DC glow discharge and thermionic filament techniques. Spatial profiles of the plasma density, plasma potential, and electron temperature are measured using Langmuir probes. We present initial experimental measurements of density and temperature profiles in the FPS device. Experimental and theoretical studies of low frequency oscillations observed in the FPS device are also presented.

  1. Nonlinear frequency coupling in dual radio-frequency driven atmospheric pressure plasmas

    SciTech Connect

    Waskoenig, J.; Gans, T.

    2010-05-03

    Plasma ionization, and associated mode transitions, in dual radio-frequency driven atmospheric pressure plasmas are governed through nonlinear frequency coupling in the dynamics of the plasma boundary sheath. Ionization in low-power mode is determined by the nonlinear coupling of electron heating and the momentary local plasma density. Ionization in high-power mode is driven by electron avalanches during phases of transient high electric fields within the boundary sheath. The transition between these distinctly different modes is controlled by the total voltage of both frequency components.

  2. Electrospray on superhydrophobic nozzles treated with argon and oxygen plasma

    NASA Astrophysics Data System (ADS)

    Byun, Doyoung; Lee, Youngjong; Tran, Si Bui Quang; Nugyen, Vu Dat; Kim, Sanghoon; Park, Baeho; Lee, Sukhan; Inamdar, Niraj; Bau, Haim H.

    2008-03-01

    We report on a simple process to fabricate electrohydrodynamic spraying devices with superhydrophobic nozzles. These devices are useful, among other things, in mass spectrometry and printing technology. The superhydrophobic nozzle is created by roughening the surface of the polyfluorotetraethylene (PTFE) by argon and oxygen plasma treatment. We have developed a polymer-based electrospray device with a flat, superhydrophobic nozzle capable of maintaining a high contact angle and stable jetting.

  3. Surface modification of polymers by atomic oxygen using ECR plasma

    NASA Astrophysics Data System (ADS)

    Abdul majeed, Riyadh M. A.; Datar, A.; Bhoraskar, S. V.; Bhoraskar, V. N.

    2007-05-01

    Polyimide (PI) and fluorinated ethylene propylene (FEP) samples were exposed to atomic oxygen ions of average energy ˜12 eV and flux ˜5 × 10 13 ions cm -2 s -1, produced in an ECR plasma. The fluence of the oxygen ions was varied from sample to sample over a range from ˜5 × 10 16 to 2 × 10 17 ions cm -2. The pre- and the post-irradiated samples were characterized by the contact angle, AFM and XPS techniques. The results indicate that the surface roughness of the polyimide increased from ˜7 to ˜65 nm, that of the FEP from ˜5 to ˜28 nm and the surface regions of both polyimide and FEP changed from hydrophobic to hydrophilic after exposure to atomic oxygen ions. The XPS results reveal that the concentrations of carbon, fluorine and oxygen changed even at a fluence of ˜10 17 ions cm -2 of the atomic oxygen ions. The results of the present study reveal that significant changes have been induced in the surface morphology and adhesion properties of polyimide and FEP after exposure to atomic oxygen ions.

  4. Surface plasma source with saddle antenna radio frequency plasma generator

    SciTech Connect

    Dudnikov, V.; Johnson, R. P.; Murray, S.; Pennisi, T.; Piller, C.; Santana, M.; Stockli, M.; Welton, R.

    2012-02-15

    A prototype RF H{sup -} surface plasma source (SPS) with saddle (SA) RF antenna is developed which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with small AlN discharge chambers and different antennas and magnetic field configurations were tested in the plasma source test stand. A prototype SA SPS was installed in the Spallation Neutron Source (SNS) ion source test stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency up to 1.6 mA/kW. Control experiments with H{sup -} beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma gun has been designed. A saddle antenna SPS with water cooling is fabricated for high duty factor testing.

  5. Surface plasma source with saddle antenna radio frequency plasma generator.

    PubMed

    Dudnikov, V; Johnson, R P; Murray, S; Pennisi, T; Piller, C; Santana, M; Stockli, M; Welton, R

    2012-02-01

    A prototype RF H(-) surface plasma source (SPS) with saddle (SA) RF antenna is developed which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with small AlN discharge chambers and different antennas and magnetic field configurations were tested in the plasma source test stand. A prototype SA SPS was installed in the Spallation Neutron Source (SNS) ion source test stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency up to 1.6 mA∕kW. Control experiments with H(-) beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma gun has been designed. A saddle antenna SPS with water cooling is fabricated for high duty factor testing.

  6. Coupled microwave ECR and radio-frequency plasma source for plasma processing

    DOEpatents

    Tsai, Chin-Chi; Haselton, Halsey H.

    1994-01-01

    In a dual plasma device, the first plasma is a microwave discharge having its own means of plasma initiation and control. The microwave discharge operates at electron cyclotron resonance (ECR), and generates a uniform plasma over a large area of about 1000 cm.sup.2 at low pressures below 0.1 mtorr. The ECR microwave plasma initiates the second plasma, a radio frequency (RF) plasma maintained between parallel plates. The ECR microwave plasma acts as a source of charged particles, supplying copious amounts of a desired charged excited species in uniform manner to the RF plasma. The parallel plate portion of the apparatus includes a magnetic filter with static magnetic field structure that aids the formation of ECR zones in the two plasma regions, and also assists in the RF plasma also operating at electron cyclotron resonance.

  7. Coupled microwave ECR and radio-frequency plasma source for plasma processing

    DOEpatents

    Tsai, C.C.; Haselton, H.H.

    1994-03-08

    In a dual plasma device, the first plasma is a microwave discharge having its own means of plasma initiation and control. The microwave discharge operates at electron cyclotron resonance (ECR), and generates a uniform plasma over a large area of about 1000 cm[sup 2] at low pressures below 0.1 mtorr. The ECR microwave plasma initiates the second plasma, a radio frequency (RF) plasma maintained between parallel plates. The ECR microwave plasma acts as a source of charged particles, supplying copious amounts of a desired charged excited species in uniform manner to the RF plasma. The parallel plate portion of the apparatus includes a magnetic filter with static magnetic field structure that aids the formation of ECR zones in the two plasma regions, and also assists in the RF plasma also operating at electron cyclotron resonance. 4 figures.

  8. Effects of driving frequency on properties of inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Godyak, Valery; Kolobov, Vladimir

    2016-10-01

    Inductively coupled plasma (ICP) can be maintained over a wide range of driving frequencies from 50 Hz up to GHz. In this paper, we analyze how the properties of ICP depend on driving frequency ω. With respect to the time of ion transport to the walls, τd and the electron energy relaxation time τɛ three operating regimes are distinguished. The quasi-static regime, ωτd << 1 , the high-frequency regime, ωτɛ >> 1 and the intermediate dynamic regime, 1 /τd < ω <1 /τɛ. In the quasi-static regime, plasma density oscillates significantly over the field period. In the high-frequency regime, the plasma density and the electron energy distribution function (EEDF) are constant. In the dynamic regime, the plasma density is constant, while the EEDF varies over the field period. Depending on ICP configuration, the induced by the coil magnetic fields inside ICP, Bc can be zero or not. For example, in ICP maintained by a long helical coil with the plasma current flowing outside the coil, Bc = 0 , while when the plasma current flows inside the coil, Bc ≠ 0 . We show that in the latter case, in the quasi-static regimes, electrons become magnetized over a significant part of the period that may strongly affect the plasma properties. Examples of ICP simulations in different frequency regimes will be demonstrated in this paper.

  9. Oxygen Plasma Modification of Poss-Coated Kapton(Registered TradeMark) HN Films

    NASA Technical Reports Server (NTRS)

    Wohl, C. J.; Belcher, M. A.; Ghose, S.; Connell, J. W.

    2008-01-01

    The surface energy of a material depends on both surface composition and topographic features. In an effort to modify the surface topography of Kapton(Registered TradeMark) HN film, organic solutions of a polyhedral oligomeric silsesquioxane, octakis(dimethylsilyloxy)silsesquioxane (POSS), were spray-coated onto the Kapton(Registered TradeMark) HN surface. Prior to POSS application, the Kapton(Registered TradeMark) HN film was activated by exposure to radio frequency (RF)-generated oxygen plasma. After POSS deposition and solvent evaporation, the films were exposed to various durations of RF-generated oxygen plasma to create a topographically rich surface. The modified films were characterized using optical microscopy, attenuated total reflection infrared (ATR-IR) spectroscopy, and high-resolution scanning electron microscopy (HRSEM). The physical properties of the modified films will be presented.

  10. Reactive oxygen species controllable non-thermal helium plasmas for evaluation of plasmid DNA strand breaks

    NASA Astrophysics Data System (ADS)

    Young Kim, Jae; Lee, Dong-Hoon; Ballato, John; Cao, Weiguo; Kim, Sung-O.

    2012-11-01

    Non-thermal, oxygen-rich helium plasmas were investigated to achieve an enhanced reactive oxygen species concentration at low voltage driving conditions. A non-thermal plasma device was fabricated based on a theta-shaped tube, and its potential was investigated for use in topological alteration of plasmid DNA. The optical emission spectra of the plasma showed that the oxygen flow affected the plasma properties, even though an oxygen plasma was not produced. The plasmid DNA strand breaks became more significant with the addition of oxygen flow to the helium in a single hollow, theta-shaped tube with other experimental conditions being unchanged.

  11. Optical Frequency Domain Visualization of Electron Beam Driven Plasma Wakefields

    NASA Astrophysics Data System (ADS)

    Zgadzaj, Rafal; Downer, M. C.; Muggli, Patric; Yakimenko, Vitaly; Babzien, Marcus; Kusche, Karl; Fedurin, Mikhail

    2010-11-01

    Beam-driven plasma wakefield accelerators (PWFA), such as the ``plasma afterburner,'' are a promising approach for significantly increasing the particle energies of conventional accelerators. The study and optimization of PWFA would benefit from an experimental correlation between the parameters of the drive bunch, the accelerated bunch and the corresponding, accelerating plasma wave structure. However, the plasma wave structure has not yet been observed directly in PWFA. We will report our current work on noninvasive optical Frequency Domain Interferometric (FDI) and Holographic (FDH) visualization of beam-driven plasma waves. Both techniques employ two laser pulses (probe and reference) co-propagating with the particle drive-beam and its plasma wake. The reference pulse precedes the drive bunch, while the probe overlaps the plasma wave and maps its longitudinal and transverse structure. The experiment is being developed at the BNL/ATF Linac to visualize wakes generated by two and multi-bunch drive beams.

  12. Operating a radio-frequency plasma source on water vapor.

    PubMed

    Nguyen, Sonca V T; Foster, John E; Gallimore, Alec D

    2009-08-01

    A magnetically enhanced radio-frequency (rf) plasma source operating on water vapor has an extensive list of potential applications. In this work, the use of a rf plasma source to dissociate water vapor for hydrogen production is investigated. This paper describes a rf plasma source operated on water vapor and characterizes its plasma properties using a Langmuir probe, a residual gas analyzer, and a spectrometer. The plasma source operated first on argon and then on water vapor at operating pressures just over 300 mtorr. Argon and water vapor plasma number densities differ significantly. In the electropositive argon plasma, quasineutrality requires n(i) approximately = n(e), where n(i) is the positive ion density. But in the electronegative water plasma, quasineutrality requires n(i+) = n(i-) + n(e). The positive ion density and electron density of the water vapor plasma are approximately one and two orders of magnitude lower, respectively, than those of argon plasma. These results suggest that attachment and dissociative attachment are present in electronegative water vapor plasma. The electron temperature for this water vapor plasma source is between 1.5 and 4 eV. Without an applied axial magnetic field, hydrogen production increases linearly with rf power. With an axial magnetic field, hydrogen production jumps to a maximum value at 500 W and then saturates with rf power. The presence of the applied axial magnetic field is therefore shown to enhance hydrogen production.

  13. Role of the ion plasma frequency in RF sheaths

    NASA Astrophysics Data System (ADS)

    Waelbroeck, F. L.; Hazeltine, R. D.; Xiang, N.

    1999-11-01

    Semiconductor etching relies on rf biasing of the substrate to produce a suitable distribution of energetic ions. The properties of the resulting oscillating sheath depend on two parameters: the ratio of the bias amplitude to the electron temperature, and the ratio of the ion plasma frequency to the rf frequency. In industrial applications, V_rf>> T_e, and nonlinear effects are important. For such large bias the dynamics of the oscillating sheath can be divided into three regimes according to the ratio of the rf frequency to the plasma frequency at the entrance of the sheath and that at the surface of the substrate. Liebermann has given an analytic solution in the high frequency regime. With the increase in plasma density, however, the ion plasma frequency often exceeds the standard rf frequency of 13.56 KHz. We present an analytic solution for the sheath dynamics in the opposite, low-frequency regime. We compare the two regimes, giving particular attention to the distribution of ion energy at the substrate.

  14. Measuring ionospheric electron density using the plasma frequency probe

    SciTech Connect

    Jensen, M.D.; Baker, K.D. )

    1992-02-01

    During the past decade, the plasma frequency probe (PFP) has evolved into an accurate, proven method of measuring electron density in the ionosphere above about 90 km. The instrument uses an electrically short antenna mounted on a sounding rocket that is immersed in the plasma and notes the frequency where the antenna impedance is large and nonreactive. This frequency is closely related to the plasma frequency, which is a direct function of free electron concentration. The probe uses phase-locked loop technology to follow a changing electron density. Several sections of the plasma frequency probe circuitry are unique, especially the voltage-controlled oscillator that uses both an electronically tuned capacitor and inductor to give the wide tuning range needed for electron density measurements. The results from two recent sounding rocket flights (Thunderstorm II and CRIT II) under vastly different plasma conditions demonstrate the capabilities of the PFP and show the importance of in situ electron density measurements of understanding plasma processes. 9 refs.

  15. Treatment Characteristics of Polysaccharides and Endotoxin Using Oxygen Plasma Produced by RF Discharge

    NASA Astrophysics Data System (ADS)

    Kitazaki, Satoshi; Hayashi, Nobuya; Goto, Masaaki

    2010-10-01

    Treatment of polysaccharides and endotoxin were attempted using oxygen plasma produced by RF discharge. Oxygen radicals observed by optical light emission spectra are factors of decomposition of polysaccharides and endotoxin. Fourier transform infrared spectra indicate that most of chemical bonds in the polysaccharides are dissociated after irradiation of the oxygen plasma. Also, the decomposition rate of endotoxin was approximately 90% after irradiation of the oxygen plasma for 180 min.

  16. Treatment Characteristics of Polysaccharides and Endotoxin Using Oxygen Plasma Produced by RF Discharge

    SciTech Connect

    Kitazaki, Satoshi; Hayashi, Nobuya; Goto, Masaaki

    2010-10-13

    Treatment of polysaccharides and endotoxin were attempted using oxygen plasma produced by RF discharge. Oxygen radicals observed by optical light emission spectra are factors of decomposition of polysaccharides and endotoxin. Fourier transform infrared spectra indicate that most of chemical bonds in the polysaccharides are dissociated after irradiation of the oxygen plasma. Also, the decomposition rate of endotoxin was approximately 90% after irradiation of the oxygen plasma for 180 min.

  17. Electromagnetic radiation trapped in the magnetosphere above the plasma frequency

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Shaw, R. R.

    1973-01-01

    An electromagnetic noise band is frequently observed in the outer magnetosphere by the Imp 6 spacecraft at frequencies from about 5 to 20 kHz. This noise band generally extends throughout the region from near the plasmapause boundary to near the magnetopause boundary. The noise typically has a broadband field strength of about 5 microvolts/meter. The noise band often has a sharp lower cutoff frequency at about 5 to 10 kHz, and this cutoff has been identified as the local electron plasma frequency. Since the plasma frequency in the plasmasphere and solar wind is usually above 20 kHz, it is concluded that this noise must be trapped in the low-density region between the plasmapause and magnetopause boundaries. The noise bands often contain a harmonic frequency structure which suggests that the radiation is associated with harmonics of the electron cyclotron frequency.

  18. The kinetics of energetic O‑ ions in oxygen discharge plasmas

    NASA Astrophysics Data System (ADS)

    Ponomarev, A. A.; Aleksandrov, N. L.

    2017-04-01

    Monte Carlo simulation was used to study the translational relaxation of energetic O‑ ions produced by dissociative electron attachment to O2 molecules in oxygen plasmas in a strong electric field. Initial O‑ ions have rather high energies and are more reactive than the ions reaching equilibrium with the electric field. Therefore, there is a noticeable probability that the energetic O‑ ions participate in endothermic reactions prior to energy relaxation of these ions. The probabilities of charge exchange, electron detachment and ion impact vibrational excitation of O2 molecules were calculated versus the reduced electric field. It was shown that up to 6% of energetic O‑ ions produced in oxygen by dissociative electron attachment to O2 molecules are rapidly transformed to {{{{O}}}2}- ions due to charge exchange collisions. The probability of electron detachment from energetic O‑ ions and the probability of vibrational excitation were smaller that the probability of charge exchange. Estimates showed that the increase in the effective rates of the ion–molecule reactions due to high reactivity of energetic O‑ ions can be important in oxygen plasmas for reduced electric fields of 50–100 Td.

  19. Variable dual-frequency electrostatic wave launcher for plasma applications.

    PubMed

    Jorns, Benjamin; Sorenson, Robert; Choueiri, Edgar

    2011-12-01

    A variable tuning system is presented for launching two electrostatic waves concurrently in a magnetized plasma. The purpose of this system is to satisfy the wave launching requirements for plasma applications where maximal power must be coupled into two carefully tuned electrostatic waves while minimizing erosion to the launching antenna. Two parallel LC traps with fixed inductors and variable capacitors are used to provide an impedance match between a two-wave source and a loop antenna placed outside the plasma. Equivalent circuit analysis is then employed to derive an analytical expression for the normalized, average magnetic flux density produced by the antenna in this system as a function of capacitance and frequency. It is found with this metric that the wave launcher can couple to electrostatic modes at two variable frequencies concurrently while attenuating noise from the source signal at undesired frequencies. An example based on an experiment for plasma heating with two electrostatic waves is used to demonstrate a procedure for tailoring the wave launcher to accommodate the frequency range and flux densities of a specific two-wave application. This example is also used to illustrate a method based on averaging over wave frequencies for evaluating the overall efficacy of the system. The wave launcher is shown to be particularly effective for the illustrative example--generating magnetic flux densities in excess of 50% of the ideal case at two variable frequencies concurrently--with a high adaptability to a number of plasma dynamics and heating applications.

  20. Variable dual-frequency electrostatic wave launcher for plasma applications

    NASA Astrophysics Data System (ADS)

    Jorns, Benjamin; Sorenson, Robert; Choueiri, Edgar

    2011-12-01

    A variable tuning system is presented for launching two electrostatic waves concurrently in a magnetized plasma. The purpose of this system is to satisfy the wave launching requirements for plasma applications where maximal power must be coupled into two carefully tuned electrostatic waves while minimizing erosion to the launching antenna. Two parallel LC traps with fixed inductors and variable capacitors are used to provide an impedance match between a two-wave source and a loop antenna placed outside the plasma. Equivalent circuit analysis is then employed to derive an analytical expression for the normalized, average magnetic flux density produced by the antenna in this system as a function of capacitance and frequency. It is found with this metric that the wave launcher can couple to electrostatic modes at two variable frequencies concurrently while attenuating noise from the source signal at undesired frequencies. An example based on an experiment for plasma heating with two electrostatic waves is used to demonstrate a procedure for tailoring the wave launcher to accommodate the frequency range and flux densities of a specific two-wave application. This example is also used to illustrate a method based on averaging over wave frequencies for evaluating the overall efficacy of the system. The wave launcher is shown to be particularly effective for the illustrative example—generating magnetic flux densities in excess of 50% of the ideal case at two variable frequencies concurrently—with a high adaptability to a number of plasma dynamics and heating applications.

  1. Surface modification of argon/oxygen plasma treated vulcanized ethylene propylene diene polymethylene surfaces for improved adhesion with natural rubber

    NASA Astrophysics Data System (ADS)

    Basak, Ganesh C.; Bandyopadhyay, Abhijit; Neogi, Sudarsan; Bhowmick, Anil K.

    2011-01-01

    Vulcanized ethylene propylene diene polymethylene (EPDM) rubber surface was treated in a radio frequency capacitatively coupled low pressure argon/oxygen plasma to improve adhesion with compounded natural rubber (NR) during co-vulcanization. The plasma modified surfaces were analyzed by means of contact angle measurement, surface energy, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray sulfur mapping and atomic force microscopy. Several experimental variables such as plasma power, length of exposure time and composition of the argon-oxygen gas mixture were considered. It was delineated that plasma treatment changed both surface composition and roughness, and consequently increased peel strength. The change in surface composition was mainly ascribed to the formation of C-O and -Cdbnd O functional groups on the vulcanized surfaces. A maximum of 98% improvement in peel strength was observed after plasma treatment.

  2. Transient electromagnetic behaviour in inductive oxygen and argon-oxygen plasmas

    NASA Astrophysics Data System (ADS)

    Chadwick, A. R.; Herdrich, G.; Kim, M.; Dally, B.

    2016-12-01

    In order to develop inductive electric propulsion as a flexible, throttleable technology for future space operations, a greater understanding of discharge transitions within the inductive plasma generator discharge chamber is required. This paper presents a non-intrusive method to determine the conditions under which transitions between the capacitive, low inductive, and high inductive regimes occur with greater accuracy, as well as determining the proportion of a single discharge cycle the plasma spends in either capacitive or inductive regime. Such a method allows a more robust method of classification of inductive discharges than previously available and can be applied to numerous gases. This approach presents an advantage over previous methods which relied on strongly radiating or thermally reactive gases to exhibit certain behaviour (due to the restriction of classical diagnostics on such high power sources) before a transition could be confirmed. This paper presents results from the proposed method applied to a pure oxygen plasma as well as two combinations of argon and oxygen (at 1:1 and 3:2 Ar:O2 volumetric ratios) in order to assess the tunability of electromagnetic regime transitions through modifications of gas composition rather than mechanical alterations. Transitions to the higher inductive mode were observed for much lower input powers for the argon-oxygen blends, as was expected, allowing final discharge conditions to occupy the inductive regime for 94% and 85% of a single discharge cycle for the 3:2 and 1:1 Ar:O2 mixtures, respectively. Pure oxygen achieved a maximum inductive proportion of 71% by comparison.

  3. Ignition and monitoring technique for plasma processing of multicell superconducting radio-frequency cavities

    SciTech Connect

    Doleans, Marc

    2016-12-27

    In this study, an in-situ plasma processing technique has been developed at the Spallation Neutron Source (SNS) to improve the performance of the superconducting radio-frequency (SRF) cavities in operation. The technique uses a low-density reactive neon-oxygen plasma at room-temperature to improve the surface work function, to help remove adsorbed gases on the RF surface and to reduce its secondary emission yield. SNS SRF cavities are six-cell elliptical cavities and the plasma typically ignites in the cell where the electric field is the highest. This article will detail a technique that was developed to ignite and monitor the plasma in each cell of the SNS cavities.

  4. Ignition and monitoring technique for plasma processing of multicell superconducting radio-frequency cavities

    DOE PAGES

    Doleans, Marc

    2016-12-27

    In this study, an in-situ plasma processing technique has been developed at the Spallation Neutron Source (SNS) to improve the performance of the superconducting radio-frequency (SRF) cavities in operation. The technique uses a low-density reactive neon-oxygen plasma at room-temperature to improve the surface work function, to help remove adsorbed gases on the RF surface and to reduce its secondary emission yield. SNS SRF cavities are six-cell elliptical cavities and the plasma typically ignites in the cell where the electric field is the highest. This article will detail a technique that was developed to ignite and monitor the plasma in eachmore » cell of the SNS cavities.« less

  5. A Single-Probe-Beam, Dual-Frequency Plasma Polarimeter

    NASA Astrophysics Data System (ADS)

    Munro, Blair; Hicks, Nathaniel

    2016-10-01

    A plasma polarimeter instrument is conceived that comprises a single microwave probe beam alternating between two discrete frequencies. The method is similar to a double-heterodyne approach proposed earlier, but reduces system complexity and cost by avoiding a frequency-swept source. The instrument uses a single detector per beamline. Initial synthetic diagnostic testing of the instrument design is presented, and the prospects for further cost and space saving by way of additive manufacturing of instrument quasi-optical components are considered. A test bench setup for initial testing of the dual-frequency source and optical path is described, as is the plan for magnetized plasma measurements in a new plasma laboratory facility at the University of Alaska Anchorage. Supported by UAA Elizabeth Tower Endowment and Complex Systems Group.

  6. Interaction of non-equilibrium oxygen plasma with sintered graphite

    NASA Astrophysics Data System (ADS)

    Cvelbar, Uroš

    2013-03-01

    Samples made from sintered graphite with grain size of about 10 μm were exposed to highly non-equilibrium oxygen plasma created in a borosilicate glass tube by an electrodeless RF discharge. The density of charged particles was about 7 × 1015 m-3 and the neutral oxygen atom density 6 × 1021 m-3. The sample temperature was determined by a calibrated IR detector while the surface modifications were quantified by XPS and water drop techniques. The sample surface was rapidly saturated with carbonyl groups. Prolonged treatment of samples caused a decrease in concentration of the groups what was explained by thermal destruction. Therefore, the created functional groups were temperature dependent. The heating of samples resulted in extensive chemical interaction between the O atoms and samples what was best monitored by decreasing of the O atom density with increasing sample temperature. The saturation with functional groups could be restored only after cooling down of the samples and repeated short plasma treatment at low temperature.

  7. Low-frequency instabilities and plasma turbulence

    NASA Technical Reports Server (NTRS)

    Ilic, D. B.

    1973-01-01

    A theoretical and experimental study is reported of steady-state and time-dependent characteristics of the positive column and the hollow cathode discharge (HCD). The steady state of a non-isothermal, cylindrical positive column in an axial magnetic field is described by three moment equations in the plasma approximation. Volume generation of electron-ion pairs by single-stage ionization, the presence of axial current, and collisions with neutrals are considered. The theory covers the range from the low pressure, collisionless regime to the intermediate pressure, collisional regime. It yields radial profiles of the charged particle velocities, density, potential, electron and ion temperatures, and demonstrates similarity laws for the positive column. The results are compared with two moment theories and with experimental data on He, Ar and Hg found in the literature for a wide range of pressures. A simple generalization of the isothermal theory for an infinitely long cylinder in an axial magnetic field to the case of a finite column with axial current flow is also demonstrated.

  8. High frequency plasma generators for ion thruster applications

    NASA Technical Reports Server (NTRS)

    Divergilio, W. F.; Goede, H.; Komatsu, G. K.; Christensen, T.

    1981-01-01

    Two concepts for high frequency discharge ion thrusters are described. Both sources are designed for use with 30 cm grid sets and argon propellant and utilize multi-cusp permanent magnet geometries for plasma confinement. The RF induction source is a conventional design representing a synthesis of the RIT and multi-cusp concepts. The preliminary data (without system optimization) indicate a discharge efficiency comparable to that obtained in 30 cm hollow cathode multi-cusp argon thrusters. The electron cyclotron heating source is electrodeless and exhibits plasma characteristics which should lead to greatly reduced discharge chamber and screen sputter rates with the optimization of the magnetic fields, microwave frequency, and feed configuration.

  9. Frequency Domain Tomography Of Evolving Laser-Plasma Accelerator Structures

    SciTech Connect

    Dong Peng; Reed, Stephen; Kalmykov, Serguei; Shvets, Gennady; Downer, Mike

    2009-01-22

    Frequency Domain Holography (FDH), a technique for visualizing quasistatic objects propagating near the speed of light, has produced 'snapshots' of laser wakefields, but they are averaged over structural variations that occur during propagation through the plasma medium. Here we explore via simulations a generalization of FDH--that we call Frequency Domain Tomography (FDT)--that can potentially record a time sequence of quasistatic snapshots, like the frames of a movie, of the wake structure as it propagates through the plasma. FDT utilizes a several probe-reference pulse pairs that propagate obliquely to the drive pulse and wakefield, along with tomographic reconstruction algorithms similar to those used in medical CAT scans.

  10. Low-frequency flute instabilities of a bounded plasma column.

    NASA Technical Reports Server (NTRS)

    Rognlien, T. D.

    1973-01-01

    Derivation of exact solutions for unstable waves (called flute waves) which occur in a radially bounded plasma column at frequencies below the ion cyclotron frequency. Both analytical and numerical solutions are presented for the m = 1 and m = 2 azimuthal modes for a variety of radial electric field profiles. It is shown that the behavior of the flute waves can depend sensitively on the radial extent of the plasma column. Moreover, it is found that the m = 1 mode and the m = 2 mode do not respond in the same way to changes in the radial boundary position or in the electric field profile.

  11. Cross-Frequency Coupling of Plasma Waves in the Magnetosphere

    NASA Astrophysics Data System (ADS)

    Khazanov, G. V.

    2014-12-01

    Wave-particle and wave-wave interactions are crucial elements of magnetosphere and ionosphere plasma dynamics. Such interactions provide a channel of energy redistribution between different plasma populations, and lead to connections between physical processes developing on different spatial and temporal scales. The lower hybrid waves (LHWs) are particularly interesting for plasma dynamics, because they couple well with both electrons and ions. The excitation of LHWs is a widely discussed mechanism of interaction between plasma species in space and is one of the unresolved questions of magnetospheric multi-ion plasmas. It is demonstrated that large-amplitude Alfven and/or EMIC waves, in particular those associated with lower frequency (LF) turbulence, may generate LHWs in the auroral zone and ring current region and in some cases this serves as the Alfven and/or EMIC waves saturation mechanism. We believe that this described scenario, as well as some other cross-frequency coupling of plasma waves processes that will be discussed in this presentation, can play a vital role in various parts of the magnetospheric plasma, especially in the places under investigation by the NASA THEMIS and Van Allen Probes (formerly known as the Radiation Belt Storm Probes (RBSP)) missions.

  12. Very high frequency plasma reactant for atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Oh, Il-Kwon; Yoo, Gilsang; Yoon, Chang Mo; Kim, Tae Hyung; Yeom, Geun Young; Kim, Kangsik; Lee, Zonghoon; Jung, Hanearl; Lee, Chang Wan; Kim, Hyungjun; Lee, Han-Bo-Ram

    2016-11-01

    Although plasma-enhanced atomic layer deposition (PE-ALD) results in several benefits in the formation of high-k dielectrics, including a low processing temperature and improved film properties compared to conventional thermal ALD, energetic radicals and ions in the plasma cause damage to layer stacks, leading to the deterioration of electrical properties. In this study, the growth characteristics and film properties of PE-ALD Al2O3 were investigated using a very-high-frequency (VHF) plasma reactant. Because VHF plasma features a lower electron temperature and higher plasma density than conventional radio frequency (RF) plasma, it has a larger number of less energetic reaction species, such as radicals and ions. VHF PE-ALD Al2O3 shows superior physical and electrical properties over RF PE-ALD Al2O3, including high growth per cycle, excellent conformality, low roughness, high dielectric constant, low leakage current, and low interface trap density. In addition, interlayer-free Al2O3 on Si was achieved in VHF PE-ALD via a significant reduction in plasma damage. VHF PE-ALD will be an essential process to realize nanoscale devices that require precise control of interfaces and electrical properties.

  13. Wettability interpretation of oxygen plasma modified poly(methyl methacrylate).

    PubMed

    Chai, Jinan; Lu, Fuzhi; Li, Baoming; Kwok, Daniel Y

    2004-12-07

    Poly(methyl methacrylate) (PMMA) has been modified via a dc pulsed oxygen plasma for different treatment times. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS), optical profilometer, zeta potential, and advancing contact angle measurements. The measured advancing contact angles of water decreased considerably as a function of discharge. Several oxygen-based functionalities (carbonyl, carboxyl, carbonate, etc.) were detected by XPS, while zeta potential measurements confirmed an increase in negative charge for the treated PMMA surface. Evaluating the correlation between the concentration of polar chemical species and zeta potential, we found that increase in surface hydrophilicity results from the coeffect due to incorporation of oxygen functional groups and creation of charge states. The electrical double layer (EDL) effect was also considered in contact angle interpretation by introducing an additional surface tension term into Young's equation. We also found that EDL contribution to the solid-liquid interfacial tension is negligible and can be safely ignored for the systems considered here.

  14. Afterglow chemistry of atmospheric-pressure helium-oxygen plasmas with humid air impurity

    NASA Astrophysics Data System (ADS)

    Murakami, Tomoyuki; Niemi, Kari; Gans, Timo; O'Connell, Deborah; Graham, William G.

    2014-04-01

    The formation of reactive species in the afterglow of a radio-frequency-driven atmospheric-pressure plasma in a fixed helium-oxygen feed gas mixture (He+0.5%O2) with humid air impurity (a few hundred ppm) is investigated by means of an extensive global plasma chemical kinetics model. As an original objective, we explore the effects of humid air impurity on the biologically relevant reactive species in an oxygen-dependent system. After a few milliseconds in the afterglow environment, the densities of atomic oxygen (O) decreases from 1015 to 1013 cm-3 and singlet delta molecular oxygen (O2(1D)) of the order of 1015 cm-3 decreases by a factor of two, while the ozone (O3) density increases from 1014 to 1015 cm-3. Electrons and oxygen ionic species, initially of the order of 1011 cm-3, recombine much faster on the time scale of some microseconds. The formation of atomic hydrogen (H), hydroxyl radical (OH), hydroperoxyl (HO2), hydrogen peroxide (H2O2), nitric oxide (NO) and nitric acid (HNO3) resulting from the humid air impurity as well as the influence on the afterglow chemistry is clarified with particular emphasis on the formation of dominant reactive oxygen species (ROS). The model suggests that the reactive species predominantly formed in the afterglow are major ROS O2(1D) and O3 (of the order of 1015 cm-3) and rather minor hydrogen- and nitrogen-based reactive species OH, H2O2, HNO3 and NO2/NO3, of which densities are comparable to the O-atom density (of the order of 1013 cm-3). Furthermore, the model quantitatively reproduces the experimental results of independent O and O3 density measurements.

  15. Dynamics of a pulsed inductively coupled oxygen plasma

    NASA Astrophysics Data System (ADS)

    Zaka-ul-Islam, Mujahid

    2016-11-01

    Inductively coupled plasma system (ICPs) is extensively used for a wide range of nanofabrication applications. The ICPs operated in a pulsed or power modulated mode has shown several advantages compared to the continuous discharge. In this work, the plasma dynamics in a planar coil pulsed inductively coupled plasma system (ICPs) operated in oxygen has been investigated, using phase and space resolved optical emission spectroscopy. It is well-known that the ICPs operates in two distinct operational modes as a function of power known as E and H modes, generated dominantly by capacitive and inductive couplings, respectively. The measurements show that the discharge ignites due a capacitive coupling (in the E-mode) and later transits to the H-mode as a function of time. The inductive coupling, however, starts during the E-mode along with capacitive coupling. The relative contribution of inductive coupling increases until the discharge reaches the E-H transition where the growth rate of inductive coupling becomes much faster. It is found that the time to reach E-H transition decreases with the pressure. At the E-H transition, the total emission has a spike-like feature (i.e., it first achieves a peak emission which later decreases and finally settles to a lower value). The 2D images of the discharge show that at the time of peak total-emission, the discharge structure is sharp and bright, which later decreases in brightness and becomes diffusive.

  16. Effect of resonance in external radio-frequency circuit on very high frequency plasma discharge

    SciTech Connect

    Rauf, Shahid; Chen Zhigang; Collins, Ken

    2010-05-15

    A fully electromagnetic plasma model for an asymmetric capacitively coupled plasma discharge is used to understand the interaction between the external radio-frequency (rf) distributed circuit and the plasma. The plasma is excited using a 150 MHz rf source connected to the top electrode, the bottom electrode is connected to a shorted transmission line, and the electrodes are separated from the chamber walls through dielectric rings. Under typical conditions, the electron density peaks in the center of the plasma chamber due to the standing electromagnetic wave and the rf current from the top electrode primarily returns through the bottom electrode. When the electrical length of the bottom transmission line is adjusted such that it presents a large (open-circuit) impedance at the plasma chamber interface, the rf return current shifts from the bottom electrode to the chamber wall. As a consequence, the peak in electron density also moves from the center of the chamber toward its outer periphery.

  17. Optical Frequency Domain Visualization of Electron Beam Driven Plasma Wakefields

    SciTech Connect

    Zgadzaj, Rafal; Downer, Michael C.; Muggli, Patric; Yakimenko, Vitaly; Kusche, Karl; Fedurin, Michhail; Babzien, Marcus

    2010-11-04

    Bunch driven plasma wakefield accelerators (PWFA), such as the 'plasma afterburner', are a promising emerging method for significantly increasing the energy output of conventional particle accelerators. The study and optimization of this method would benefit from an experimental correlation of the drive bunch parameters and the accelerated particle parameters with the corresponding plasma wave structure. However, the plasma wave structure has not been observed directly so far. We will report ongoing development of a noninvasive optical Frequency Domain Interferometric (FDI) and Holographic (FDH) diagnostics of bunch driven plasma wakes. Both FDI and FDH have been previously demonstrated in the case of laser driven wakes. These techniques employ two laser pulses co-propagating with the drive particle bunch and the trailing plasma wave. One pulse propagates ahead of the drive bunch and serves as a reference, while the second is overlapped with the plasma wave and probes its structure. The multi-shot FDI and single-shot FDH diagnostics permit direct noninvasive observation of longitudinal and transverse structure of the plasma wakes. The experiment is being developed at the 70 MeV Linac in the Accelerator Test Facility at Brookhaven National Laboratory to visualize wakes generated by two and multi-bunch drive beams.

  18. Optical Frequency Domain Visualization of Electron Beam Driven Plasma Wakefields

    NASA Astrophysics Data System (ADS)

    Zgadzaj, Rafal; Downer, Michael C.; Muggli, Patric; Yakimenko, Vitaly; Kusche, Karl; Fedurin, Michhail; Babzien, Marcus

    2010-11-01

    Bunch driven plasma wakefield accelerators (PWFA), such as the "plasma afterburner," are a promising emerging method for significantly increasing the energy output of conventional particle accelerators [1]. The study and optimization of this method would benefit from an experimental correlation of the drive bunch parameters and the accelerated particle parameters with the corresponding plasma wave structure. However, the plasma wave structure has not been observed directly so far. We will report ongoing development of a noninvasive optical Frequency Domain Interferometric (FDI) [2] and Holographic (FDH) [3] diagnostics of bunch driven plasma wakes. Both FDI and FDH have been previously demonstrated in the case of laser driven wakes. These techniques employ two laser pulses co-propagating with the drive particle bunch and the trailing plasma wave. One pulse propagates ahead of the drive bunch and serves as a reference, while the second is overlapped with the plasma wave and probes its structure. The multi-shot FDI and single-shot FDH diagnostics permit direct noninvasive observation of longitudinal and transverse structure of the plasma wakes. The experiment is being developed at the 70 MeV Linac in the Accelerator Test Facility at Brookhaven National Laboratory to visualize wakes generated by two [4] and multi-bunch [5] drive beams.

  19. Sterilization Effect of Wet Oxygen Plasma in the Bubbling Method.

    PubMed

    Tamazawa, Kaoru; Shintani, Hideharu; Tamazawa, Yoshinori; Shimauchi, Hidetoshi

    2015-01-01

    A new low-temperature sterilization method to replace the ethylene oxide gas sterilization is needed. Strong bactericidal effects of OH and O2H radicals are well known. The purpose of this study was to evaluate the sterilization effect of wet oxygen ("O2+H2O") plasma in the bubbling method, confirming the effect of humidity. Sterility assurance was confirmed by using a biological indicator (Geobacillus stearothermophilus ATCC7953, Namsa, USA). One hundred and eight samples (10(5) spores/carrier) were divided into three groups of 36 in each for treatment with a different type of gas (O2, O2+H2O, Air+H2O). Plasma processing was conducted using a plasma ashing apparatus (13.56 MHz, PACK-3(®), Y. A. C., Japan) under various gas pressures (13, 25, 50 Pa) and gas flows (50, 100, 200 sccm). Fixed plasma treatment parameters were power at 150 W, temperature of 60 ℃, treatment time of 10 min. The samples after treatment were incubated in trypticase soy broth at 58 ℃ for 72 h. The negative culture rate in the "O2+H2O" group was significantly (Mantel-Haenszel procedure, p<0.001) higher than in the other gas groups. It is suggested that the significant sterilization effect of the "O2+H2O" group depends on the bubbling method which is the method of introducing vapor into the chamber. The bubbling method seems able to generate OH and O2H radicals in a stable way.

  20. External control of ion waves in a plasma by high frequency fields

    DOEpatents

    Kaw, P.K.; Dawson, J.M.

    1973-12-18

    An apparatus and method are described for stabilizing plasma instabilities, in a magnetically confined plasma column by transmitting into the plasma high frequency electromagnetic waves at a frequency close to the electron plasma frequency. The said frequencies, e.g., are between the plasma frequency and 1.5 times the plasma frequency at a power level below the level for producing parametric instabilities in a plasma having temperatures from below 10 eV to about 10 keV or more, at densities from below 10/sup 13/ to above 10/sup 18/ particles/cm/sup 3/. (Official Gazette)

  1. Excitation and Ionisation dynamics in high-frequency plasmas

    NASA Astrophysics Data System (ADS)

    O'Connell, D.

    2008-07-01

    Non-thermal low temperature plasmas are widely used for technological applications. Increased demands on plasma technology have resulted in the development of various discharge concepts based on different power coupling mechanisms. Despite this, power dissipation mechanisms in these discharges are not yet fully understood. Of particular interest are low pressure radio-frequency (rf) discharges. The limited understanding of these discharges is predominantly due to the complexity of the underlying mechanisms and difficult diagnostic access to important parameters. Optical measurements are a powerful diagnostic tool offering high spatial and temporal resolution. Optical emission spectroscopy (OES) provides non-intrusive access, to the physics of the plasma, with comparatively simple experimental requirements. Improved advances in technology and modern diagnostics now allow deeper insight into fundamental mechanisms. In low pressure rf discharges insight into the electron dynamics within the rf cycle can yield vital information. This requires high temporal resolution on a nano-second time scale. The optical emission from rf discharges exhibits temporal variations within the rf cycle. These variations are particularly strong, in for example capacitively coupled plasmas (CCPs), but also easily observable in inductively coupled plasmas (ICPs), and can be exploited for insight into power dissipation. Interesting kinetic and non-linear coupling effects are revealed in capacitive systems. The electron dynamics exhibits a complex spatio-temporal structure. Excitation and ionisation, and, therefore, plasma sustainment is dominated through directed energetic electrons created through the dynamics of the plasma boundary sheath. In the relatively simple case of an asymmetric capacitively coupled rf plasma the complexity of the power dissipation is exposed and various mode transitions can be clearly observed and investigated. At higher pressure secondary electrons dominate the

  2. Exponential frequency spectrum and Lorentzian pulses in magnetized plasmas

    SciTech Connect

    Pace, D. C.; Shi, M.; Maggs, J. E.; Morales, G. J.; Carter, T. A.

    2008-12-15

    Two different experiments involving pressure gradients across the confinement magnetic field in a large plasma column are found to exhibit a broadband turbulence that displays an exponential frequency spectrum for frequencies below the ion cyclotron frequency. The exponential feature has been traced to the presence of solitary pulses having a Lorentzian temporal signature. These pulses arise from nonlinear interactions of drift-Alfven waves driven by the pressure gradients. In both experiments the width of the pulses is narrowly distributed resulting in exponential spectra with a single characteristic time scale. The temporal width of the pulses is measured to be a fraction of a period of the drift-Alfven waves. The experiments are performed in the Large Plasma Device (LAPD-U) [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] operated by the Basic Plasma Science Facility at the University of California, Los Angeles. One experiment involves a controlled, pure electron temperature gradient associated with a microscopic (6 mm gradient length) hot electron temperature filament created by the injection a small electron beam embedded in the center of a large, cold magnetized plasma. The other experiment is a macroscopic (3.5 cm gradient length) limiter-edge experiment in which a density gradient is established by inserting a metallic plate at the edge of the nominal plasma column of the LAPD-U. The temperature filament experiment permits a detailed study of the transition from coherent to turbulent behavior and the concomitant change from classical to anomalous transport. In the limiter experiment the turbulence sampled is always fully developed. The similarity of the results in the two experiments strongly suggests a universal feature of pressure-gradient driven turbulence in magnetized plasmas that results in nondiffusive cross-field transport. This may explain previous observations in helical confinement devices, research tokamaks, and arc plasmas.

  3. Mechanisms of polymer degradation using an oxygen plasma generator

    NASA Technical Reports Server (NTRS)

    Colony, Joe A.; Sanford, Edward L.

    1987-01-01

    An RF oxygen plasma generator was used to produce polymer degradation which appears to be similar to that which has been observed in low Earth orbit. Mechanisms of this type of degradation were studied by collecting the reaction products in a cryogenic trap and identifying the molecular species using infrared, mass spectral, and X-ray diffraction techniques. No structurally dependent species were found from Kapton, Teflon, or Saran polymers. However, very reactive free radical entities are produced during the polymer degradation, as well as carbon dioxide and water. Reactions of the free radicals with the glass reaction vessel, with copper metal in the cold trap, and with a triphenyl phosphate scavenger in the cold trap, demonstrated the reactivity of the primary products.

  4. The effect of intermediate frequency on sheath dynamics in collisionless current driven triple frequency capacitive plasmas

    NASA Astrophysics Data System (ADS)

    Sharma, S.; Mishra, S. K.; Kaw, P. K.; Turner, M. M.

    2017-01-01

    The Capacitively Coupled Plasma discharge featuring operation in current driven triple frequency configuration has analytically been investigated, and the outcome is verified by utilising the 1D3V particle-in-cell (PIC) simulation code. In this analysis, the role of middle frequency component of the applied signal has precisely been explored. The discharge parameters are seen to be sensitive to the ratio of the chosen middle frequency to lower and higher frequencies for fixed amplitudes of the three frequency components. On the basis of analysis and PIC simulation results, the middle frequency component is demonstrated to act as additional control over sheath potential, electron sheath heating, and ion energy distribution function (iedf) of the plasma discharge. For the electron sheath heating, effect of the middle frequency is seen to be pronounced as it approaches to the lower frequency component. On the other hand, for the iedf, the control is more sensitive as the middle frequency approaches towards the higher frequency. The PIC estimate for the electron sheath heating is found to be in reasonably good agreement with the analytical prediction based on the Kaganovich formulation.

  5. PIC simulation of reactive radio-frequency plasma

    NASA Astrophysics Data System (ADS)

    Matthias, Paul; Kahnfeld, Daniel; Lueskow, Karl; Bandelow, Gunnar; Schneider, Ralf; Kemnitz, Stefan; Duras, Julia

    2016-10-01

    Reactive plasmas are important for industrial applications. For sputter processes and plasma etching especially asymmetric capacitively coupled plasmas with a radio-frequency modulated voltage are used. The latest experimental results show an unexpected high-energy peak of negative ions at the grounded anode, depending on the cathode material. Here the Particle-in-Cell (PIC) method was used to simulate this experiment. The main mechanism for the effect is identified as the production of negative ions near the surface of the cathode. In a one dimensional simulation the negative ions are trapped inside the plasma because of the symmetric potential. Thus it was shown that these high-energy peaks of negative ions at the anode only appear in asymmetric discharges, due to the self-bias voltage. To reproduce the asymmetry a two dimensional model will be used in the future. German Space Agency DLR Project 50 RS 1510.

  6. Low frequency nonlinear waves in electron depleted magnetized nonthermal plasmas

    NASA Astrophysics Data System (ADS)

    Mobarak Hossen, Md.; Sahadat Alam, Md.; Sultana, Sharmin; Mamun, A. A.

    2016-11-01

    A theoretical study on the ultra-low frequency small but finite amplitude solitary waves has been carried out in an electron depleted magnetized nonthermal dusty plasma consisting of both polarity (positively charged as well as negatively charged) inertial massive dust particles and nonextensive q distributed ions. The reductive perturbation technique is employed to derive the ZakharovKuznetsov (ZK) equation. The basic features of low frequency solitary wave are analyzed via the solution of ZK equation. It is observed that the intrinsic properties (e.g., polarity, amplitude, width, etc.) of dust-acoustic (DA) solitary waves (SWs) are significantly influenced by the effects external magnetic field, obliqueness, nonextensivity of ions, and the ratio of ion number density to the product of electron and negative dust number density. The findings of our results may be useful to explain the low frequency nonlinear wave propagation in some plasma environments like cometary tails, the earth polar mesosphere, Jupiter's magnetosphere, etc.

  7. In situ oxygen plasma cleaning of microswitch surfaces—comparison of Ti and graphite electrodes

    NASA Astrophysics Data System (ADS)

    Oh, Changho; Streller, Frank; Ashurst, W. Robert; Carpick, Robert W.; de Boer, Maarten P.

    2016-11-01

    Ohmic micro- and nanoswitches are of interest for a wide variety of applications including radio frequency communications and as low power complements to transistors. In these switches, it is of paramount importance to maintain surface cleanliness in order to prevent frequent failure by tribopolymer growth. To prepare surfaces, an oxygen plasma clean is expected to be beneficial compared to a high temperature vacuum bakeout because of shorter cleaning time (<5 min compared to ~24 h) and active removal of organic contaminants. We demonstrate that sputtering of the electrode material during oxygen plasma cleaning is a critical consideration for effective cleaning of switch surfaces. With Ti electrodes, a TiO x layer forms that increases electrical contact resistance. When plasma-cleaned using graphite electrodes, the resistance of Pt-coated microswitches exhibit a long lifetime with consistently low resistance (<0.5 Ω variation over 300 million cycles) if the test chamber is refilled with ultra-high purity nitrogen and if the devices are not exposed to laboratory air. Their current-voltage characteristic is also linear at the millivolt level. This is important for nanoswitches which will be operated in that range.

  8. Electron scattering cross sections for the modelling of oxygen-containing plasmas*

    NASA Astrophysics Data System (ADS)

    Alves, Luís Lemos; Coche, Philippe; Ridenti, Marco Antonio; Guerra, Vasco

    2016-06-01

    This work proposes a set of electron scattering cross sections for molecular and atomic oxygen, with interest for the modelling of oxygen-containing plasmas. These cross sections, compiled for kinetic energies up to 1 keV, are part of the IST-LISBON database with LXCat, being used as input data to the LoKI (LisbOn KInetics) numerical code. The cross sections for ground-state molecular oxygen describe elastic and inelastic collision mechanisms, the latter including rotational excitations/de-excitations (treated using either a discrete or a continuous approach), vibrational and electronic excitations (including dissociation), dissociative attachment and ionisation. This set yields calculated swarm parameters that reproduce measurements within 5-20% (transport parameters) and within a factor of 2 difference (Townsend coefficients), for reduced electric fields in the range 10-3-103 Td. The cross sections describing the kinetics of atomic oxygen by electron-impact comprise elastic mechanisms, electronic excitation and ionisation from O(3P) ground-state, dissociation of O2(X,a,b) (including dissociative ionisation and attachment) and of O3, and detachment. These cross sections are indirectly validated, together with other elementary data for oxygen, by comparing the densities of O((4S0)3 p 5P) obtained from the self-consistent modelling and from calibrated optical emission spectroscopy diagnostics of microwave-sustained micro-plasmas in dry air (80% N2: 20% O2), produced using a surface-wave excitation (2.45 GHz frequency) within a small radius capillary ( R = 345 μm) at low pressure ( p = 300 Pa). The calculated densities are in good qualitative agreement with measurements, overestimating them by a factor ˜1.5.

  9. Electron scattering cross sections for the modelling of oxygen-containing plasmas

    NASA Astrophysics Data System (ADS)

    Lemos Alves, Luís; Coche, Philippe; Ridenti, Marco Antonio; Guerra, Vasco

    2016-05-01

    This work proposes a set of electron scattering cross sections for molecular and atomic oxygen, with interest for the modelling of oxygen-containing plasmas. These cross sections, compiled for kinetic energies up to 1 keV, are part of the IST-LISBON database with LXCat, being used as input data to the LoKI (LisbOn KInetics) numerical code. The cross sections for ground-state molecular oxygen describe elastic and inelastic collision mechanisms, the latter including rotational excitations/de-excitations (treated using either a discrete or a continuous approach), vibrational and electronic excitations (including dissociation), dissociative attachment and ionisation. This set yields calculated swarm parameters that reproduce measurements within 5-20% (transport parameters) and within a factor of 2 difference (Townsend coefficients), for reduced electric fields in the range 10-3-103 Td. The cross sections describing the kinetics of atomic oxygen by electron-impact comprise elastic mechanisms, electronic excitation and ionisation from O(3P) ground-state, dissociation of O2(X,a,b) (including dissociative ionisation and attachment) and of O3, and detachment. These cross sections are indirectly validated, together with other elementary data for oxygen, by comparing the densities of O((4S0)3p 5P) obtained from the self-consistent modelling and from calibrated optical emission spectroscopy diagnostics of microwave-sustained micro-plasmas in dry air (80% N2: 20% O2), produced using a surface-wave excitation (2.45 GHz frequency) within a small radius capillary (R = 345 μm) at low pressure (p = 300 Pa). The calculated densities are in good qualitative agreement with measurements, overestimating them by a factor ˜1.5. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  10. Tunable optical absorption and interactions in graphene via oxygen plasma

    NASA Astrophysics Data System (ADS)

    Santoso, Iman; Singh, Ram Sevak; Gogoi, Pranjal Kumar; Asmara, Teguh Citra; Wei, Dacheng; Chen, Wei; Wee, Andrew T. S.; Pereira, Vitor M.; Rusydi, Andrivo

    2014-02-01

    We report significant changes of optical conductivity (σ1) in single-layer graphene induced by mild oxygen plasma exposure and explore the interplay between carrier doping, disorder, and many-body interactions from their signatures in the absorption spectrum. The first distinctive effect is the reduction of the excitonic binding energy that can be extracted from the renormalized saddle point resonance at 4.64 eV. Secondly, σ1 is nearly completely suppressed (σ1≪σ0) below an exposure-dependent threshold in the near-infrared range. The clear steplike suppression follows the Pauli blocking behavior expected for doped monolayer graphene. The nearly zero residual conductivity below ω ˜ 2EF can be interpreted as arising from the weakening of the electronic self-energy. Our data shows that mild oxygen exposure can be used to controllably dope graphene without introducing the strong physical and chemical changes that are common in other approaches to oxidized graphene, allowing a controllable manipulation of the optical properties of graphene.

  11. Low Frequency Waves in the Plasma Environment Around the Shuttle

    NASA Technical Reports Server (NTRS)

    Vayner, Boris V.; Ferguson, Dale C.

    1996-01-01

    As a part of the SAMPIE (The Solar Array Module Plasma Interaction Experiment) program, the Langmuir probe (LP) was employed to measure plasma characteristics during the flight of STS-62. The whole set of data could be divided into two parts: (1) low frequency sweeps to determine voltage-current characteristics and to find the electron temperature and number density; (2) high frequency turbulence (HFT) data caused by electromagnetic noise around the Shuttle. Broadband noise was observed at 250-20,000 Hz frequencies. Measurements were performed in ram conditions; thus, it seems reasonable to believe that the influence of spacecraft operations on plasma parameters was minimized. It is shown that ion acoustic waves were observed, and two kinds of instabilities are suggested for explanation of the origin of these waves. According to the purposes of SAMPIE, samples of solar cells were placed in the cargo bay of the Shuttle, and high negative bias voltages were applied to them to initiate arcing between these cells and the surrounding plasma. The arcing onset was registered by special counters, and data were obtained that included the amplitudes of current, duration of each arc, and the number of arcs per one experiment. The LP data were analyzed for two different situations: with arcing and without arcing. Electrostatic noise spectra for both situations and a theoretical explanation of the observed features are presented in this paper.

  12. Extraction of ions and electrons from audio frequency plasma source

    NASA Astrophysics Data System (ADS)

    Haleem, N. A.; Abdelrahman, M. M.; Ragheb, M. S.

    2016-09-01

    Herein, the extraction of high ion / electron current from an audio frequency (AF) nitrogen gas discharge (10 - 100 kHz) is studied and investigated. This system is featured by its small size (L= 20 cm and inner diameter = 3.4 cm) and its capacitive discharge electrodes inside the tube and its high discharge pressure ˜ 0.3 Torr, without the need of high vacuum system or magnetic fields. The extraction system of ion/electron current from the plasma is a very simple electrode that allows self-beam focusing by adjusting its position from the source exit. The working discharge conditions were applied at a frequency from 10 to 100 kHz, power from 50 - 500 W and the gap distance between the plasma meniscus surface and the extractor electrode extending from 3 to 13 mm. The extracted ion/ electron current is found mainly dependent on the discharge power, the extraction gap width and the frequency of the audio supply. SIMION 3D program version 7.0 package is used to generate a simulation of ion trajectories as a reference to compare and to optimize the experimental extraction beam from the present audio frequency plasma source using identical operational conditions. The focal point as well the beam diameter at the collector area is deduced. The simulations showed a respectable agreement with the experimental results all together provide the optimizing basis of the extraction electrode construction and its parameters for beam production.

  13. Effect of oxygen plasma on the properties of tantalum oxide films

    SciTech Connect

    Kalygina, V. M. Zarubin, A. N.; Novikov, V. A.; Petrova, Yu. S.; Skakunov, M. S.; Tolbanov, O. P.; Tyazhev, A. V.; Yaskevich, T. M.

    2010-09-15

    The effect of oxygen plasma on the leakage current, permittivity, and the dielectric loss tangent of Ta{sub 2}O{sub 5} thin layers (300-400 nm) is studied. It is suggested to treat tantalum oxide films in oxygen plasma to control their electrical and dielectric characteristics.

  14. Surface Evaluation by X-Ray Photoelectron Spectroscopy of High Performance Polyimide Foams After Exposure to Oxygen Plasma

    NASA Technical Reports Server (NTRS)

    Melendez, Orlando; Hampton, Michael D.; Williams, Martha K.; Brown, Sylvia F.; Nelson, Gordon L.; Weiser, Erik S.

    2002-01-01

    Aromatic polyimides have been attractive in the aerospace and electronics industries for applications such as cryogenic insulation, flame retardant panels and structural subcomponents. Newer to the arena of polyimides is the synthesis of polyimide foams and their applications. In the present work, three different, closely related, polyimide foams developed by NASA Langley Research Center (LaRC) are studied by X-ray Photoelectron Spectroscopy (XPS) after exposure to radio frequency generated Oxygen Plasma. Although polyimide films exposure to atomic oxygen and plasma have been studied previously and reported, the data relate to films and not foams. Foams have much more surface area and thus present new information to be explored. Understanding degradation mechanisms and properties versus structure, foam versus solid is of interest and fundamental to the application and protection of foams exposed to atomic oxygen in Low Earth Orbit (LEO).

  15. Low-Frequency Waves in Cold Three-Component Plasmas

    NASA Astrophysics Data System (ADS)

    Fu, Qiang; Tang, Ying; Zhao, Jinsong; Lu, Jianyong

    2016-09-01

    The dispersion relation and electromagnetic polarization of the plasma waves are comprehensively studied in cold electron, proton, and heavy charged particle plasmas. Three modes are classified as the fast, intermediate, and slow mode waves according to different phase velocities. When plasmas contain positively-charged particles, the fast and intermediate modes can interact at the small propagating angles, whereas the two modes are separate at the large propagating angles. The near-parallel intermediate and slow waves experience the linear polarization, circular polarization, and linear polarization again, with the increasing wave number. The wave number regime corresponding to the above circular polarization shrinks as the propagating angle increases. Moreover, the fast and intermediate modes cause the reverse change of the electromagnetic polarization at the special wave number. While the heavy particles carry the negative charges, the dispersion relations of the fast and intermediate modes are always separate, being independent of the propagating angles. Furthermore, this study gives new expressions of the three resonance frequencies corresponding to the highly-oblique propagation waves in the general three-component plasmas, and shows the dependence of the resonance frequencies on the propagating angle, the concentration of the heavy particle, and the mass ratio among different kinds of particles. supported by National Natural Science Foundation of China (Nos. 11303099, 41531071 and 41574158), and the Youth Innovation Promotion Association CAS

  16. Variation of antioxidative activity and growth enhancement of Brassicaceae induced by low-pressure oxygen plasma

    NASA Astrophysics Data System (ADS)

    Ono, Reoto; Hayashi, Nobuya

    2015-06-01

    The mechanism of growth enhancement induced by active oxygen species generated in an oxygen plasma is investigated. The plant growth enhancement induced by the active oxygen species would relate to an antioxidative activity, which is one of the biological responses. The amount of generated active oxygen species is varied by the oxygen gas pressure in a low-pressure RF glow discharge plasma. The antioxidative activity of sprouts of Brassicaceae induced by the oxygen plasma is maximized at pressures between 30 and 40 Pa, whereas the antioxidative activity becomes small at around 60 and 80 Pa. The pressure dependence of the antioxidative activity of sprout stems is opposite to that of the stem length of the sprouts. The growth enhancement would be induced by the increase in the concentration of active oxygen species in plants owing to the decrease in the amount of antioxidative substances.

  17. Ion energy distributions in dual frequency RF plasmas

    NASA Astrophysics Data System (ADS)

    Hatton, Peter; Rees, John; Bort, Sam; Seymour, Dave

    2015-09-01

    For many surface-processing applications involving plasmas operated at RF frequencies it has been found helpful to combine two sources of power operating at different frequencies. By choosing suitable input powers at the two frequencies and varying the phase relationship set between the two inputs, the energy distributions (IEDs) for the ions arriving at the target surface can be optimised. There have been, however, only a limited number of published reports of measured or modelled distributions. In the present work IEDs for both positive and negative ions formed in plasmas in argon and nitrous oxide have been measured for mass-identified ions in two different reactors, one of which is a parallel-plate, capacitatively-coupled, system and the other is an inductively-coupled system. Typical data for 13.56 and 27.1 MHz inputs are presented for a range of phase relationships. The IEDs show clearly significant differences between the data for different species of ions which result in part from the ion-molecule collisions occurring, particularly in the plasma/surface sheath regions.

  18. Transient plasma potential in pulsed dual frequency inductively coupled plasmas and effect of substrate biasing

    NASA Astrophysics Data System (ADS)

    Mishra, Anurag; Yeom, Geun Young

    2016-09-01

    An electron emitting probe in saturated floating potential mode has been used to investigate the temporal evolution of plasma potential and the effect of substrate RF biasing on it for pulsed dual frequency (2 MHz/13.56 MHz) inductively coupled plasma (ICP) source. The low frequency power (P2MHz) has been pulsed at 1 KHz and a duty ratio of 50%, while high frequency power (P13.56MHz) has been used in continuous mode. The substrate has been biased with a separate bias power at (P12.56MHz) Argon has been used as a discharge gas. During the ICP power pulsing, three distinct regions in a typical plasma potential profile, have been identified as `initial overshoot', pulse `on-phase' and pulse `off-phase'. It has been found out that the RF biasing of the substrate significantly modulates the temporal evolution of the plasma potential. During the initial overshoot, plasma potential decreases with increasing RF biasing of the substrate, however it increases with increasing substrate biasing for pulse `on-phase' and `off-phase'. An interesting structure in plasma potential profile has also been observed when the substrate bias is applied and its evolution depends upon the magnitude of bias power. The reason of the evolution of this structure may be the ambipolar diffusion of electron and its dependence on bias power.

  19. Electron ranaway and ion-ion plasma formation in afterglow low-pressure plasma of oxygen-containing gas mixtures

    NASA Astrophysics Data System (ADS)

    Kudryavtsev, Anatoly; Bogdanov, Eugene; Kosykh, Nikolay; Gutsev, Sergey

    2012-10-01

    Experimental investigation of temporal evolution of charged plasma species in afterglow plasma of oxygen-containing mixtures have been investigated. The probe VAC and the time dependence of the saturation positive and negative particles currents to a probe in a fixed bias voltage were performed. The decay of afterglow low-pressure electronegative gas plasmas take place in two distinct stages (the electron-ion stage, and the ion-ion stage) as it was shown in [1] for pure oxygen. In the first stage, the negative ions are locked within a discharge volume and plasma is depleted of electrons and positive ions. The electron density decay is faster, than exponential, and practically all electrons leave plasma volume during finite time followed by the ion--ion (electron-free) plasma formation. The decay of the ion-ion plasma depends on the presence of detachment. With a large content of electronegative gas (oxygen) in a mixture, when there is a ``detachment particles,'' a small fraction of the electrons appearing as a result of the detachment continue to hold all negative ions in the discharge volume. In this case, the densities of all charged plasma components decay according to the same exponential law with a characteristic detachment time. At a low oxygen content in the gas mixture there is no detachment and plasma decays by an ion--ion ambipolar diffusion mechanism.[4pt][1]. S.A.Gutsev, A.A.Kudryavtsev, V.A.Romanenko. Tech.Phys. 40, 1131, (1995).

  20. Spectroscopic Measurements of Radio Frequency Plasmas in Supercritical Fluids

    SciTech Connect

    Maehara, Tsunehiro; Iwamae, Atsushi; Kawashima, Ayato

    2010-10-29

    Spectroscopic measurements of radio frequency (rf) plasma were performed under high pressure CO{sub 2} conditions (5 and 7 MPa) and supercritical (sc)CO{sub 2} conditions (8-20 MPa). The temperatures evaluated from C{sub 2} Swan bands increased from 3600 K to 4600 K with increasing pressure. The broadening and shifting of the O I line profile ({approx}777 nm) of rf plasma was observed under scCO{sub 2} conditions. The width of the line profile increased with increasing pressure. The reason for the broadening and shifting is still unclear because the present theory used to explain them is not valid for such high pressure conditions. Further, the broadening of the Ar I line profile ({approx}811.5 nm) in rf plasmas was observed under atmospheric Ar (0.1 MPa), high pressure Ar conditions (1-4 MPa), and scAr condition (5 MPa); the observation of the O I line profile in CO{sub 2} plasmas is difficult in this pressure range owing to its weak intensity therein. Similar to the case of the O I line in CO{sub 2} plasmas, the reason for the broadening of the Ar I line profile at 5 MPa is unclear.

  1. Effect of radio frequency discharge power on dusty plasma parameters

    SciTech Connect

    Sheridan, T. E.

    2009-08-01

    The parameters of a two-dimensional dusty plasma consisting of six, 9 mum diameter particles trapped inside a radio frequency (rf) plasma sheath have been measured as a function of rf power in a 13.5 mtorr (1.8 Pa) argon discharge. The center-of-mass and breathing frequencies are found by projecting the cluster's Brownian motion onto the associated normal mode. The center-of-mass frequency (i.e., radial confinement) is insensitive to rf power. The Debye shielding parameter kappa, as found from the breathing frequency, increases from approx =0.5 to 2 as the square root of rf power. The Debye length decreases from approx =2.7 to 0.7 mm as the inverse of the square root of rf power. The average particle charge qapprox =-17 000e is effectively independent of rf power. These results are consistent with an electron temperature that is independent of rf power and an ion density that is directly proportional to rf power, where the Debye length is determined by the ion density in combination with the electron temperature.

  2. Determination of the neutral oxygen atom density in a plasma reactor loaded with metal samples

    NASA Astrophysics Data System (ADS)

    Mozetic, Miran; Cvelbar, Uros

    2009-08-01

    The density of neutral oxygen atoms was determined during processing of metal samples in a plasma reactor. The reactor was a Pyrex tube with an inner diameter of 11 cm and a length of 30 cm. Plasma was created by an inductively coupled radiofrequency generator operating at a frequency of 27.12 MHz and output power up to 500 W. The O density was measured at the edge of the glass tube with a copper fiber optics catalytic probe. The O atom density in the empty tube depended on pressure and was between 4 and 7 × 1021 m-3. The maximum O density was at a pressure of about 150 Pa, while the dissociation fraction of O2 molecules was maximal at the lowest pressure and decreased with increasing pressure. At about 300 Pa it dropped below 10%. The measurements were repeated in the chamber loaded with different metallic samples. In these cases, the density of oxygen atoms was lower than that in the empty chamber. The results were explained by a drain of O atoms caused by heterogeneous recombination on the samples.

  3. LiNbO 3 exposed to radio-frequency plasma

    NASA Astrophysics Data System (ADS)

    Turcicova, H.; Vacik, J.; Cervena, J.; Perina, V.; Polcarova, M.; Bradler, J.; Zelezny, V.; Zemek, J.

    1998-05-01

    Radio-frequency (27.12 MHz) glow discharge in H 2 and O, have been used for surface modification of LiNbO 3 wafers. The properties of plasma modified surface layers were dependent on the gas pressure and radio frequency (RF) input power. At pressures below 1 Torr of H 2 and input powers of 1-10 W/cm 3 , a low-resistance layer was created with a sheet resistivity of 2.6 mΩ cm. At pressures of several Torrs, an Li density drop up to a depth of 1 μm appeared, accompanied by OH - radical formation. The sample processing in oxygen plasma was aimed at restoring light transparency of the samples, which was lost during hydrogen processing. The restoration is attainable in a short time and at much lower sample temperature than under thermal bleaching. Processing under certain plasma parameters decreased the density of point defects in the material. The methods used for characterizing the plasma-modified layers were neutron depth profiling (NDP) and Rutherford backscattering (RBS), X-ray induced photoelectron spectroscopy (XPS), X-ray diffraction, visible and infrared transmission and reflection spectroscopy. The paper summarizes the results of a four year study and suggests possible applications of the findings.

  4. Low Frequency Turbulence as the Source of High Frequency Waves in Multi-Component Space Plasmas

    NASA Technical Reports Server (NTRS)

    Khazanov, George V.; Krivorutsky, Emmanuel N.; Uritsky, Vadim M.

    2011-01-01

    Space plasmas support a wide variety of waves, and wave-particle interactions as well as wavewave interactions are of crucial importance to magnetospheric and ionospheric plasma behavior. High frequency wave turbulence generation by the low frequency (LF) turbulence is restricted by two interconnected requirements: the turbulence should be strong enough and/or the coherent wave trains should have the appropriate length. These requirements are strongly relaxed in the multi-component plasmas, due to the heavy ions large drift velocity in the field of LF wave. The excitation of lower hybrid waves (LHWs), in particular, is a widely discussed mechanism of interaction between plasma species in space and is one of the unresolved questions of magnetospheric multi-ion plasmas. It is demonstrated that large-amplitude Alfven waves, in particular those associated with LF turbulence, may generate LHW s in the auroral zone and ring current region and in some cases (particularly in the inner magnetosphere) this serves as the Alfven wave saturation mechanism. We also argue that the described scenario can playa vital role in various parts of the outer magnetosphere featuring strong LF turbulence accompanied by LHW activity. Using the data from THEMIS spacecraft, we validate the conditions for such cross-scale coupling in the near-Earth "flow-braking" magnetotail region during the passage of sharp injection/dipolarization fronts, as well as in the turbulent outflow region of the midtail reconnection site.

  5. Improved fluid simulations of radio-frequency plasmas using energy dependent ion mobilities

    SciTech Connect

    Greb, Arthur; Niemi, Kari; O'Connell, Deborah; Gans, Timo; Ennis, Gerard J.; MacGearailt, Niall

    2013-05-15

    Symmetric and asymmetric capacitively coupled radio-frequency plasmas in oxygen at 40 Pa, 300 V voltage amplitude and a discharge gap of 40 mm are investigated by means of one-dimensional numerical semi-kinetic fluid modeling on the basis of a simplified reaction scheme including the dominant positive and negative ions, background gas, and electrons. An improved treatment, by accounting for the dependence of ion mobilities on E/N, is compared to the standard approach, based on using zero-field mobility values only. The charged particle dynamics as a result of direct electron impact ionization of oxygen, secondary electron release from the electrodes, the spatial distribution of all involved particles as well as impact of geometry and model modification on ion energies is analyzed and compared to independent simulations and experiments.

  6. Characterizing low frequency plasma waves at Mars with MAVEN

    NASA Astrophysics Data System (ADS)

    Ruhunusiri, Suranga; Halekas, Jasper; Connerney, Jack; Espley, Jared; Larson, Davin; Mitchell, David L.

    2015-04-01

    We use the measurements from the Solar Wind Ion Analyzer (SWIA) and the magnetometer (MAG) instruments aboard the MAVEN spacecraft to characterize plasma waves in the Martian magnetosphere. SWIA is a toroidal energy analyzer that measures 3-d ion velocity distributions, and we use it for measuring ion moment fluctuations. MAG instrument, on the other hand, is a fluxgate magnetometer, and we use it for measuring magnetic field fluctuations. Mars is unique in the solar system because of two characteristics: it only has an induced magnetosphere with strong crustal fields at low altitudes, and it has an extended atmosphere due to its lower gravity. Due to these two characteristics, Mars presents a unique environment to study the interaction of a planetary magnetosphere and an exosphere with the solar wind. One consequence of this interaction is the excitation of low frequency plasma waves which have highest power near and below the proton gyrofrequency. Studying these waves is of interest because they can play a vital role in the mass and energy transport in the Martian magnetosphere. In this investigation, we use both ion moment fluctuations (density and velocity) and the magnetic field fluctuations to characterize these low frequency plasma waves.

  7. Surface Josephson plasma waves in layered superconductors above the plasma frequency: evidence for a negative index of refraction.

    PubMed

    Golick, V A; Kadygrob, D V; Yampol'skii, V A; Rakhmanov, A L; Ivanov, B A; Nori, Franco

    2010-05-07

    We predict a new branch of surface Josephson plasma waves (SJPWs) in layered superconductors for frequencies higher than the Josephson plasma frequency. In this frequency range, the permittivity tensor components along and transverse to the layers have different signs, which is usually associated with negative refraction. However, for these frequencies, the bulk Josephson plasma waves cannot be matched with the incident and reflected waves in the vacuum, and, instead of the negative-refractive properties, abnormal surface modes appear within the frequency band expected for bulk modes. We also discuss the excitation of high-frequency SJPWs by means of the attenuated-total-reflection method.

  8. Treatment Characteristics of Second Order Structure of Proteins Using Low-Pressure Oxygen RF Plasma

    NASA Astrophysics Data System (ADS)

    Hayashi, Nobuya; Nakahigashi, Akari; Kawaguchi, Ryutaro; Goto, Masaaki

    2010-10-01

    Removal of proteins from the surface of medical equipments is attempted using oxygen plasma produced by RF discharge. FTIR spectra indicate that the bonding of C-H and N-H in the casein protein is reduced after irradiation of oxygen plasma. Also, the second order structure of a protein such as α-helix and β-sheet are modified by the oxygen plasma. Complete removal of casein protein with the concentration of 0.016 mg/cm2 that is equivalent to remnants on the medical equipment requires two hours avoiding the damage to medical equipments.

  9. Ionospheric nf sub H resonances: Frequency shifts versus plasma conditions

    NASA Technical Reports Server (NTRS)

    Benson, R. F.

    1971-01-01

    The Alouette 2 resonances observed near the harmonics of the electron cyclotron frequency f sub H reveal frequency shifts (relative to the n(f sub H) values derived from model field calculations) which can be interpreted in terms of plasma wave dispersion effects. These effects are observed on the 2(f sub H) resonance when it is near the resonance observed close to the upper hybrid frequency f sub T. The observations suggest that an oblique echo model may be required to give a proper interpretation of the 2(f sub H) resonance. Cyclotron damping can be ignored only when the angle between the propagation vector and the direction perpendicular to the earth's magnetic field B is less than a few degrees for the 2(f sub H) wave, and less than a few tenths of a degree for the n(f sub H) waves with n 2. The negative offset of the absolute value of B inferred from the plasma resonance observations is consistent with expectations based on recent OGO 3 and OGO 5 rubidium magnetometer observations at higher altitudes in the equatorial regions.

  10. Spectroscopic measurements of high frequency plasma in supercritical carbon dioxide

    SciTech Connect

    Maehara, T.; Mukasa, S.; Takemori, T.; Watanabe, T.; Kurokawa, K.; Toyota, H.; Nomura, S.; Kawashima, A.; Iwamae, A.

    2009-03-15

    Spectroscopic measurements of high frequency (hf) plasma were performed under high pressure conditions (5 and 7 MPa) and supercritical (sc) CO{sub 2} conditions (8-20 MPa). Temperature evaluated from C{sub 2} Swan bands (d {sup 3}{pi}{sub g}{yields}a {sup 3}{pi}{sub u}) increased from 3600 to 4600 K with an increase in pressure. The first observation of broadening and shifting of the O I line profile (3p {sup 5} P{sub 3,2,1}{yields}3s {sup 5} S{sub 2}{sup 0}) of hf plasma under sc CO{sub 2} conditions was carried out. However, the origin of broadening and the shifting cannot be understood because the present theory explaining them is not valid for such high pressure conditions.

  11. Low frequency turbulence in space plasmas with dust impurities

    NASA Astrophysics Data System (ADS)

    Atamaniuk, Barbara; Volokitin, Alexander S.; Rothkaehl, Hanna

    2013-04-01

    In order to enhance our understanding of the rich plasma physical processes that drive the solar-terrestrial space environment and to create the adequate and rich services for Space Weather Program, we need to increase our ability to perform multi-point measurements by means of different sensors. Moon as the natural spacecraft can be a target for localisation the radio receiver dedicated to monitoring Earth's space environment and obtain a much more complete picture of electromagnetic plasma turbulence in different space regions than those available hitherto. Moreover this diagnostic can give the information about the localisation and property of the plasmopause, magnetosheet, magnetopause, bow shock, solar wind and radio burst and CME. It is well known that even systems with a finite number of interacting waves can be realized in the turbulent state of the active media. At the same time the essential role of dissipation of the waves suggests that, at low threshold of instability, a typical perturbed state of the plasma can be described as a finite set of interacting waves, some of which are unstable and others are strongly damped. In such cases, the number of waves remains finite, but because of competition between the instability and damping of the waves when they interact, the dynamics of the amplitudes of the waves becomes stochastic in nature and the so-called few-mode turbulence. In analyzing the conditions of the various modes of instability of nonlinear low-frequency waves and discussed the transition from quasi-periodic regime to a few-mode turbulence, and then to the fully developed turbulence, depending on the density and composition of the dust component of the plasma. An important topic for lunar missions is understanding how the charged dust behaves, roles of dust transport, levitated dust and electrodynamics around the lunar surface . It could be essential for ensuring the continued safe operation of equipment and long-term exploration. Lunar dust is

  12. Scattering of radio frequency waves by turbulence in fusion plasmas

    NASA Astrophysics Data System (ADS)

    Ram, Abhay K.

    2016-10-01

    In tokamak fusion plasmas, coherent fluctuations in the form of blobs or filaments and incoherent fluctuations due to turbulence are routinely observed in the scrape-off layer. Radio frequency (RF) electromagnetic waves, excited by antenna structures placed near the wall of a tokamak, have to propagate through the scrape-off layer before reaching the core of the plasma. While the effect of fluctuations on RF waves has not been quantified experimentally, there are telltale signs, arising from differences between results from simulations and from experiments, that fluctuations can modify the spectrum of RF waves. Any effect on RF waves in the scrape-off layer can have important experimental consequences. For example, electron cyclotron waves are expected to stabilize the deleterious neoclassical tearing mode (NTM) in ITER. Spectral and polarization changes due to scattering will modify the spatial location and profile of the current driven by the RF waves, thereby affecting the control of NTMs. Pioneering theoretical studies and complementary computer simulations have been pursued to elucidate the impact of fluctuations on RF waves. From the full complement of Maxwell's equations for cold, magnetized plasmas, it is shown that the Poynting flux in the wake of filaments develops spatial structure due to diffraction and shadowing. The uniformity of power flow into the plasma is affected by side-scattering, modifications to the wave spectrum, and coupling to plasma waves other than the incident RF wave. The Snell's law and the Fresnel equations have been reformulated within the context of magnetized plasmas. They are distinctly different from their counterparts in scalar dielectric media, and reveal new and important physical insight into the scattering of RF waves. The Snell's law and Fresnel equations are the basis for the Kirchhoff approximation necessary to determine properties of the scattered waves. Furthermore, this theory is also relevant for studying back

  13. Collisionless expansion of pulsed radio frequency plasmas. I. Front formation

    NASA Astrophysics Data System (ADS)

    Schröder, T.; Grulke, O.; Klinger, T.; Boswell, R. W.; Charles, C.

    2016-01-01

    The dynamics during plasma expansion are studied with the use of a versatile particle-in-cell simulation with a variable neutral gas density profile. The simulation is tailored to a radio frequency plasma expansion experiment [Schröder et al., J. Phys. D: Appl. Phys. 47(5), 055207 (2014)]. The experiment has shown the existence of a propagating ion front. The ion front features a strong electric field and features a sharp plasma potential drop similar to a double layer. However, the presented results of a first principle simulation show that, in general, the ion front does not have to be entangled with an electric field. The propagating electric field reflects the downstream ions, which stream with velocities up to twice as high as that of the ion front propagation. The observed ion density peak forms due to the accumulation of the reflected ions. The simulation shows that the ion front formation strongly depends on the initial ion density profile and is subject to a wave-breaking phenomenon. Virtual diagnostics in the code allow for a direct comparison with experimental results. Using this technique, the plateau forming in the wake of the plasma front could be indirectly verified in the expansion experiment. Although the simulation considers profiles only in one spatial dimensional, its results are qualitatively in a very good agreement with the laboratory experiment. It can successfully reproduce findings obtained by independent numerical models and simulations. This indicates that the effects of magnetic field structures and tangential inhomogeneities are not essential for the general expansion dynamic. The presented simulation will be used for a detailed parameter study dealt with in Paper II [Schröder et al., Phys. Plasma 23, 013512 (2016)] of this series.

  14. Scattering of radio frequency waves by blobs in tokamak plasmas

    SciTech Connect

    Ram, Abhay K.; Hizanidis, Kyriakos; Kominis, Yannis

    2013-05-15

    The density fluctuations and blobs present in the edge region of magnetic fusion devices can scatter radio frequency (RF) waves through refraction, reflection, diffraction, and coupling to other plasma waves. This, in turn, affects the spectrum of the RF waves and the electromagnetic power that reaches the core of the plasma. The usual geometric optics analysis of RF scattering by density blobs accounts for only refractive effects. It is valid when the amplitude of the fluctuations is small, of the order of 10%, compared to the background density. In experiments, density fluctuations with much larger amplitudes are routinely observed, so that a more general treatment of the scattering process is needed. In this paper, a full-wave model for the scattering of RF waves by a blob is developed. The full-wave approach extends the range of validity well beyond that of geometric optics; however, it is theoretically and computationally much more challenging. The theoretical procedure, although similar to that followed for the Mie solution of Maxwell's equations, is generalized to plasmas in a magnetic field. Besides diffraction and reflection, the model includes coupling to a different plasma wave than the one imposed by the external antenna structure. In the model, it is assumed that the RF waves interact with a spherical blob. The plasma inside and around the blob is cold, homogeneous, and imbedded in a uniform magnetic field. After formulating the complete analytical theory, the effect of the blob on short wavelength electron cyclotron waves and longer wavelength lower hybrid waves is studied numerically.

  15. Radio Frequency Field Calculations for Plasma Heating Simulations in VASIMR

    NASA Astrophysics Data System (ADS)

    Ilin, A. V.; Díaz, F. R. Chang; Squire, J. P.; Carter, M. D.

    2002-01-01

    (VASIMR)1 is plasma heating by ion-cyclotron RF heating (ICRF). Mathematical simulation helps to design an ICRF antenna, i.e. make maximal absorption of RF power into the plasma in the resonance area. Another goal of a particle simulation is design of a magnetic nozzle and optimize the performance of VASIMR2. field in the plasma, 2) ion density and velocity, 3) ion-cyclotron radio-frequency electromagnetic field. The assumptions of quasineutral and collisionless plasma are based on the range of operating VASIMR parameters. Carlo simulations for systems of million of particles in a reasonable time and without the need for a powerful supercomputer. The particle to grid weighting method is used for calculating the ion density, which is used for recalculation of the electric potential and RF field. dimensional problem to a weighted sum over two-dimensional solutions. Absorption is introduced in the cold plasma model by adding an imaginary collision frequency to the RF driven frequency, which is equivalent to adding an imaginary particle mass in the dielectric tensor elements. static and RF fields using the VASIMR code2. The VASIMR and EMIR codes are then iterated to estimate the ICRF effects on the plasma density. The iteration is performed by calculating the RF fields with the EMIR code, and using these fields to follow nonlinear ion trajectories with the VASIMR code on the gyro-frequency time scale. The ion trajectories are used to generate RF power absorption values and a density input for the next EMIR calculation. The codes are iterated until the density profile becomes reasonably stable, then the collisional absorption parameter in the EMIR code is adjusted and the iteration is continued until the power deposited by the RF system matches the power absorbed by the ion trajectories in a global sense. electric field. The solved algebraic system of equations is represented by ill-conditioned 18-diagonal matrix with complex elements. Since early development of the

  16. The role of thermal energy accommodation and atomic recombination probabilities in low pressure oxygen plasmas

    NASA Astrophysics Data System (ADS)

    Gibson, Andrew Robert; Foucher, Mickaël; Marinov, Daniil; Chabert, Pascal; Gans, Timo; Kushner, Mark J.; Booth, Jean-Paul

    2017-02-01

    Surface interaction probabilities are critical parameters that determine the behaviour of low pressure plasmas and so are crucial input parameters for plasma simulations that play a key role in determining their accuracy. However, these parameters are difficult to estimate without in situ measurements. In this work, the role of two prominent surface interaction probabilities, the atomic oxygen recombination coefficient γ O and the thermal energy accommodation coefficient α E in determining the plasma properties of low pressure inductively coupled oxygen plasmas are investigated using two-dimensional fluid-kinetic simulations. These plasmas are the type used for semiconductor processing. It was found that α E plays a crucial role in determining the neutral gas temperature and neutral gas density. Through this dependency, the value of α E also determines a range of other plasma properties such as the atomic oxygen density, the plasma potential, the electron temperature, and ion bombardment energy and neutral-to-ion flux ratio at the wafer holder. The main role of γ O is in determining the atomic oxygen density and flux to the wafer holder along with the neutral-to-ion flux ratio. It was found that the plasma properties are most sensitive to each coefficient when the value of the coefficient is small causing the losses of atomic oxygen and thermal energy to be surface interaction limited rather than transport limited.

  17. Plasma-Based Tunable High Frequency Power Limiter

    NASA Astrophysics Data System (ADS)

    Semnani, Abbas; Macheret, Sergey; Peroulis, Dimitrios

    2016-09-01

    Power limiters are often employed to protect sensitive receivers from being damaged or saturated by high-power incoming waves. Although wideband low-power limiters based on semiconductor technology are widely available, the options for high-power frequency-selective ones are very few. In this work, we study the application of a gas discharge tube (GDT) integrated in an evanescent-mode (EVA) cavity resonator as a plasma-based power limiter. Plasmas can inherently handle higher power in comparison with semiconductor diodes. Also, using a resonant structure provides the ability of having both lower threshold power and frequency-selective limiting, which are important if only a narrowband high-power signal is targeted. Higher input RF power results in stronger discharge in the GDT and consequently higher electron density which results in larger reflection. It is also possible to tune the threshold power by pre-ionizing the GDT with a DC bias voltage. As a proof of concept, a 2-GHz EVA resonator loaded by a 90-V GDT was fabricated and measured. With reasonable amount of insertion loss, the limiting threshold power was successfully tuned from 8.3 W to 590 mW when the external DC bias was varied from 0 to 80 V. The limiter performed well up to 100 W of maximum available input power.

  18. Radio frequency (rf) plasma spheroidized HA powders: powder characterization and spark plasma sintering behavior.

    PubMed

    Xu, J L; Khor, K A; Gu, Y W; Kumar, R; Cheang, P

    2005-05-01

    The present study describes the synthesis of spheroidized hydroxyapatite (HA) powders using a radio frequency (rf) inductively coupled plasma (ICP) torch. The spheroidized powders were consolidated through a spark plasma sintering (SPS) system. The microstructure and crystallographic phases in the synthesized powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Raman spectrometry. Results showed that the HA feedstock decomposed after rf plasma processing. Crystalline HA, alpha-tri-calcium phosphate (alpha-TCP), tetra-calcium phosphate (TTCP) and calcium oxide (CaO) were detected in the plasma-spheroidized powders. Raman spectra results indicated strong presence of amorphous calcium phosphate (ACP) in the spheroidized powders. The particle size distribution and specific surface area were influenced through the rf plasma working plate power levels. The sintering behavior of the rf plasma synthesized powders was analyzed through the SPS process and the results indicated that the spheroidized powders commence sintering at approximately 900 degrees C and through to 1150 degrees C. After sintering above 1100 degrees C for 3min, the relative densities of the SPS compacts reached 96% of the theoretical value. The SPS compacts were immersed in simulated body fluids (SBF) for different durations and the results confirmed their bioactivities.

  19. Control of reactive oxygen and nitrogen species production in liquid by nonthermal plasma jet with controlled surrounding gas

    NASA Astrophysics Data System (ADS)

    Ito, Taiki; Uchida, Giichiro; Nakajima, Atsushi; Takenaka, Kosuke; Setsuhara, Yuichi

    2017-01-01

    We present the development of a low-frequency nonthermal plasma-jet system, where the surrounding-gas condition of the plasma jet is precisely controlled in open air. By restricting the mixing of the ambient air into the plasma jet, the plasma jet can be selectively changed from a N2 main discharge to an O2 main discharge even in open air. In the plasma-jet system with the controlled surrounding gas, the production of reactive oxygen and nitrogen species is successfully controlled in deionized water: the concentration ratio of NO2 - to H2O2 is tuned from 0 to 0.18, and a high NO2 - concentration ratio is obtained at a N2 gas ratio of 0.80 relative to the total N2/O2 gas mixture in the main discharge gas. We also find that the NO2 - concentration is much higher in the plasma-activated medium than in the plasma-activated deionized water, which is mainly explained by the contribution of amino acids to NO2 - generation in the medium.

  20. Analytic model and frequency characteristics of plasma synthetic jet actuator

    NASA Astrophysics Data System (ADS)

    Zong, Hao-hua; Wu, Yun; Li, Ying-hong; Song, Hui-min; Zhang, Zhi-bo; Jia, Min

    2015-02-01

    This paper reports a novel analytic model of a plasma synthetic jet actuator (PSJA), considering both the heat transfer effect and the inertia of the throat gas. Both the whole cycle characteristics and the repetitive working process of PSJA can be predicted with this model. The frequency characteristics of a PSJA with 87 mm3 volume and different orifice diameters are investigated based on the analytic model combined with experiments. In the repetitive working mode, the actuator works initially in the transitional stage with 20 cycles and then in the dynamic balanced stage. During the transitional stage, major performance parameters of PSJA experience stepped growth, while during the dynamic balanced stage, these parameters are characterized by periodic variation. With a constant discharge energy of 6.9 mJ, there exists a saturated frequency of 4 kHz/6 kHz for an orifice diameter of 1 mm/1.5 mm, at which the time-averaged total pressure of the pulsed jet reaches a maximum. Between 0.5 mm and 1.5 mm, a larger orifice diameter leads to a higher saturated frequency due to the reduced jet duration time. As the actuation frequency increases, both the time-averaged cavity temperature and the peak jet velocity initially increase and then remain almost unchanged at 1600 K and 280 m/s, respectively. Besides, with increasing frequency, the mechanical energy incorporated in single pulsed jet, the expelled mass per pulse, and the time-averaged density in the cavity, decline in a stair stepping way, which is caused by the intermittent decrease of refresh stage duration in one period.

  1. Cerebral and muscle oxygen saturation measurement by a frequency-domain near-infrared spectroscopic technique

    NASA Astrophysics Data System (ADS)

    Ferrari, Marco; De Blasi, Roberto A.; Fantini, Sergio; Franceschini, Maria-Angela; Barbieri, Beniamino B.; Quaresima, Valentina; Gratton, Enrico

    1995-05-01

    Absorption and reduced scattering coefficients at 715 and 825 nm as well as hemoglobin saturation and content of the forehead and the forearm were measured by a 110 MHz frequency-domain multisource instrument. The absolute data obtained by the frequency- domain spectrometer were compared with oxygenation changes measured by a continuous wave instrument during quadriceps ischemia and postural changes. These preliminary results indicate that portable frequency-domain instruments could be very helpful to investigate brain and muscle pathophysiology.

  2. A linear radio frequency plasma reactor for potential and current mapping in a magnetized plasma

    SciTech Connect

    Faudot, E.; Devaux, S.; Moritz, J.; Heuraux, S.; Molina Cabrera, P.; Brochard, F.

    2015-06-15

    Langmuir probe measurements in front of high power ion cyclotron resonant frequency antennas are not possible or simply too noisy to be analyzed properly. A linear experiment is a radio frequency (RF) magnetized plasma discharge reactor designed to probe the rectified potential in front of such antennas but at low power level (1 kW) to next improve antenna design and mitigate sheath effects. The maximum magnetic field is 0.1 T, and the RF amplifier can work between 10 kHz and 250 MHz allowing ion cyclotron resonances for argon or helium. The first measurements with no magnetic field are presented here, especially 2D potential maps extracted from the RF compensated probe measurements yield ni ≈ 10{sup 15} m{sup −3} and Te ≈ 2 eV for RF power lower than 100 W. Series resonances in the chamber are highlighted and allow to deduce the plasma parameters from a simple equivalent impedance model of the plasma in helium gas. Next studies will be focused on magnetized plasmas and especially magnetized RF sheaths.

  3. Inactivation of Bacteria using Combined Effects of Magnetic Field, Low Pressure and Ultra Low Frequency Plasma Discharges (ULFP)

    NASA Astrophysics Data System (ADS)

    Galaly, A. R.; Zahran, H. H.

    2013-04-01

    Inactivating viable cells at very short application times has been studied using Ultra Low Frequency Plasma (ULFP) at one Kilo Hertz, using an RF source. The targeted fashion is to inactivate Escherichia coli (E. coli) in the absence and in the presence of magnetic field. Adding oxygen (O2) to argon (Ar) in the discharge leads to a complete bacterial inactivation, where the inactivation rate increased as the concentration of O2 increases. Analyses of the experimental data of the initial and final densities of viable cells, using survival curves, showed a dramatic inhibitory effect of plasma discharge to the residual survival of microbial ratio due to the influence of the magnetic field.

  4. Oxygen post-treatment of plastic surface coated with plasma polymerized silicon-containing monomers

    NASA Technical Reports Server (NTRS)

    Wydeven, T. J.; Hollanhan, J. R., Jr. (Inventor)

    1979-01-01

    The abrasion resistance of plastic surfaces coated with polymerized organosilanes can be significantly improved by post-treatment of the polymerized silane in an oxygen plasma. For optical purposes, the advantages of this post-treatment are developed with a transparent polycarbonate resin substrate coated with plasma polymerized vinyltrimethoxysilane.

  5. A mechanism for plasma waves at the harmonics of the plasma frequency foreshock boundary

    NASA Technical Reports Server (NTRS)

    Klimas, A. J.

    1982-01-01

    A bump-on-tail unstable reduced velocity distribution, constructed from data obtained at the upstream boundary of the electron foreshock by the GSFC electron spectrometer experiment on the ISEE-1 satellite, is used as the initial plasma state for a numerical integration of the 1D-Vlasov-Maxwell system of equations. The integration is carried through the growth of the instability, beyond its saturation, and well into the stabilized plasma regime. A power spectrum computed for the electric field of the stabilized plasma is dominated by a narrow peak at the Bohm-Gross frequency of the unstable field mode but also contains significant power at the harmonics of the Bohm-Gross frequency. The harmonic power is in sharp peaks which are split into closely spaced doublets. The fundamental peak at the Bohm-Gross frequency is split into a closely spaced triplet. The mechanism for excitation of the second harmonic is shown to be second order wave-wave coupling.

  6. Comparison of plasma excitation, ionization, and energy influx in single and dual frequency capacitive discharges

    NASA Astrophysics Data System (ADS)

    Sahu, B. B.; Han, Jeon G.

    2016-12-01

    Argon (Ar) plasma characteristics in a single and dual-frequency (DF), capacitively coupled plasma processing system are compared for drive frequencies 13.56 MHz, 320 MHz and their mixture as dual frequencies (DF). We present frequency dependent changes that occur in discharges in terms of plasma parameters such as plasma density, electron temperature, electron energy distribution function, optical emission, gas temperature, and metastable Ar density in a pressure range of 10-150 mTorr. Additionally, this work also presents the formulation and characterization of energy fluxes from plasma to a substrate/probe during the plasma generation. By variation of the operating pressure and plasma excitation frequency, the different contributions originating from the kinetic energy, the recombination of charge carriers such as electrons and ions at the surface along with the contributions from the neutral and excited species are determined. Data reveals that Ar metastable density in low-frequency radio frequency (RF) plasma is not a strong function of operating pressure even though plasma ionization increases with pressure. However, in the case of high-frequency and DF, the excitation of Ar metastable decreases and ionization increases due to enhanced collisions and efficient electron-neutral momentum/energy transfer. Also, data reveals that energy flux in the low-frequency RF plasmas is very high compared to that of high-frequency and DF operations.

  7. Relationship between the discharge mode and the spatial oxygen plasma distribution in a large size ferrite inductively coupled plasmas

    SciTech Connect

    Kim, Hyun Jun; Hwang, Hye Ju; Cho, Jeong Hee; Chae, Hee Sun; Kim, Dong Hwan; Chung, Chin-Wook

    2015-04-15

    The electrical characteristics and the spatial distribution of oxygen plasma according to the number of turns in ferrite inductively coupled plasmas (ferrite ICPs) are investigated. Through a new ICP model, which includes the capacitive coupling and the power loss of the ferrite material with the conventional ICP model, the variation of the oxygen discharge characteristics depending on the number of turns is simply understood by the electrical measurement, such as the antenna voltages and the currents. As the number of the turns increases, the capacitive coupling dominantly affects the spatial plasma distribution. This capacitive coupling results in a center focused density profile along the radial direction. In spite of the same discharge conditions (discharge chamber, neutral gas, and pressure), the spatial plasma distribution over 450 mm has drastic changes by increasing number of the turns. In addition, the effect of the negative species to the density profile is compared with the argon discharge characteristics at the same discharge configuration.

  8. Plasma Etching of superconducting radio frequency cavity by Ar/Cl2 capacitively coupled Plasma

    NASA Astrophysics Data System (ADS)

    Upadhyay, Janardan; Popovic, Svetozar; Valente-Feliciano, Anne-Marie; Phillips, Larry; Vuskovic, Lepsha

    2016-09-01

    We are developing plasma processing technology of superconducting radio frequency (SRF) cavities. The formation of dc self-biases due to surface area asymmetry in this type of plasma and its variation on the pressure, rf power and gas composition was measured. Enhancing the surface area of the inner electrode to reduce the asymmetry was studied by changing the contour of the inner electrode. The optimized contour of the electrode based on these measurements was chosen for SRF cavity processing. To test the effect of the plasma etching on the cavity rf performance, a 1497 MHz single cell SRF cavity is used, which previously mechanically polished, buffer chemically etched afterwards and rf tested at cryogenic temperatures for a baseline test. Plasma processing was accomplished by moving axially the inner electrode and the gas flow inlet in a step-wise manner to establish segmented plasma processing. The cavity is rf tested afterwards at cryogenic temperatures. The rf test and surface condition results are presented.

  9. Oxygen plasma ashing effects on aluminum and titanium space protective coatings

    NASA Technical Reports Server (NTRS)

    Synowicki, R.; Kubik, R. D.; Hale, J. S.; Peterkin, Jane; Nafis, S.; Woollam, John A.; Zaat, S.

    1991-01-01

    Using variable angle spectroscopic ellipsometry and atomic force microscopy (AFM), the surface roughness and oxidation of aluminum and titanium thin films have been studied as a function of substrate deposition temperature and oxygen plasma exposure. Increasing substrate deposition temperatures affect film microstructure by greatly increasing grain size. Short exposures to an oxygen plasma environment produce sharp spikes rising rapidly above the surface as seen by AFM. Ellipsometric measurements were made over a wide range of plasma exposure times, and results at longer exposure times suggest that the surface is greater than 30% void. This is qualitatively verified by the AFM images.

  10. Observation of upper drift modes in radio frequency produced magnetized plasmas with frequency above ion cyclotron frequency

    SciTech Connect

    Ghosh, Abhijit; Saha, S. K.; Chowdhury, S.; Janaki, M. S.

    2015-12-15

    In a RF produced magnetized argon plasma expanding into a larger expansion chamber, electrostatic modes propagating azimuthally in the direction of the electron diamagnetic drift and frequency greater than the ion cyclotron frequency are observed. In the radial direction, the mode amplitude peaks at a location where the radial density gradient is maximum. The modes are detected at axial locations up to 16 cm away from the entrance aperture. For fixed values of the neutral pressure and magnetic field, the mode frequency is found to be independent of the location at which it is measured. The modes exhibit drift wave characteristics revealing a radial structure with the azimuthal mode number m = 1 at the lower radial locations (r ∼ 3.0 cm) while the m = 2 mode is located in the outer region. Theoretical modeling using a local dispersion relation based on the fluid equations predicts destabilization of the modes with frequency greater than the ion-cyclotron frequency by electron-neutral collisions and exhibiting other drift wave features.

  11. Low-frequency ultrasound induces oxygen vacancies formation and visible light absorption in TiO2 P-25 nanoparticles.

    PubMed

    Osorio-Vargas, Paula A; Pulgarin, Cesar; Sienkiewicz, Andrzej; Pizzio, Luis R; Blanco, Mirta N; Torres-Palma, Ricardo A; Pétrier, Christian; Rengifo-Herrera, Julián A

    2012-05-01

    Low-frequency ultrasound (LFUS) irradiation induces morphological, optical and surface changes in the commercial nano-TiO(2)-based photocatalyst, Evonik-Degussa P-25. Low-temperature electron spin resonance (ESR) measurements performed on this material provided the first experimental evidence for the formation of oxygen vacancies (V(o)), which were also found responsible for the visible-light absorption. The V(o) surface defects might result from high-speed inter-particle collisions and shock waves generated by LFUS sonication impacting the TiO(2) particles. This is in contrast to a number of well-established technologies, where the formation of oxygen vacancies on the TiO(2) surface often requires harsh technological conditions and complicated procedures, such as annealing at high temperatures, radio-frequency-induced plasma or ion sputtering. Thus, this study reports for the first time the preparation of visible-light responsive TiO(2)-based photocatalysts by using a simple LFUS-based approach to induce oxygen vacancies at the nano-TiO(2) surface. These findings might open new avenues for synthesis of novel nano-TiO(2)-based photocatalysts capable of destroying water or airborne pollutants and microorganisms under visible light illumination.

  12. Plasma corticosteroid dynamics in channel catfish, Ictalurus punctatus (Rafinesque), during and after oxygen depletion

    USGS Publications Warehouse

    Tomasso J.R., Davis; Parker, N.C.

    1981-01-01

    Plasma corticosteroid concentrations in channel catfish, Ictalurus punctatus, (normally 1.0 ± 0.3 μg/100 ml) increased significantly (to 5.9 ± 1.2μg/100 ml) in response to acute oxygen depletion and then returned to control levels within 30 min after the dissolved oxygen concentration was increased; however, a secondary increase in plasma corticosteroid levels was observed 6 h after exposure. Corticosteroid levels also increased in fish exposed to dissolved oxygen concentration of <0.2 mg/1 for three days. Methylene blue was not effective in preventing interrenal response to low dissolved oxygen. No diurnal plasma corticosteroid rhythm was observed in fish exposed to diurnal chemical rhythms of culture ponds.

  13. Theoretical studies on kinetics of singlet oxygen in nonthermal plasma

    NASA Astrophysics Data System (ADS)

    Frolov, Mikhail P.; Ionin, Andrei A.; Kotkov, Andrei A.; Kochetov, Igor V.; Napartovich, Anatolii P.; Podmarkov, Yurii P.; Seleznev, Leonid V.; Sinitsyn, Dmitrii V.; Vagin, Nikolai P.; Yuryshev, Nikolay N.

    2004-09-01

    An idea to replace singlet delta oxygen (SDO) generator working with wet chemistry by electric discharge generator has got much attention last years. Different kinds of discharge were examined for this purpose, but without a great success. The existing theoretical models are not validated by well-characterized experimental data. To describe complicated kinetics in gas discharge with oxygen one needs to know in detail processes involving numerous electronic excited oxygen molecules and atoms. To gain new knowledge about these processes experimental studies were made on electric discharge properties in gas mixture flow with independent control of inlet SDO concentration. The theoretical model extended to include minor additives like oxygen atoms, water molecules, ozone was developed. Comparison with careful experimental measurements of electric characteristics along with gas composition allows us to verify the model and make theoretical predictions more reliable. Results of numerical simulations using this model for an electron-beam sustained discharge are reported and compared with the experimental data.

  14. Radio-Frequency Plasma Cleaning of a Penning Malmberg Trap

    NASA Technical Reports Server (NTRS)

    Sims, William Herbert, III; Martin, James; Pearson, J. Boise; Lewis, Raymond

    2005-01-01

    Radio-frequency-generated plasma has been demonstrated to be a promising means of cleaning the interior surfaces of a Penning-Malmberg trap that is used in experiments on the confinement of antimatter. {Such a trap was reported in Modified Penning-Malmberg Trap for Storing Antiprotons (MFS-31780), NASA Tech Briefs, Vol. 29, No. 3 (March 2005), page 66.} Cleaning of the interior surfaces is necessary to minimize numbers of contaminant atoms and molecules, which reduce confinement times by engaging in matter/antimatter-annihilation reactions with confined antimatter particles. A modified Penning-Malmberg trap like the one described in the cited prior article includes several collinear ring electrodes (some of which are segmented) inside a tubular vacuum chamber, as illustrated in Figure 1. During operation of the trap, a small cloud of charged antiparticles (e.g., antiprotons or positrons) is confined to a spheroidal central region by means of a magnetic field in combination with DC and radiofrequency (RF) electric fields applied via the electrodes. In the present developmental method of cleaning by use of RF-generated plasma, one evacuates the vacuum chamber, backfills the chamber with hydrogen at a suitable low pressure, and uses an RF-signal generator and baluns to apply RF voltages to the ring electrodes. Each ring is excited in the polarity opposite that of the adjacent ring. The electric field generated by the RF signal creates a discharge in the low-pressure gas. The RF power and gas pressure are adjusted so that the plasma generated in the discharge (see Figure 2) physically and chemically attacks any solid, liquid, and gaseous contaminant layers on the electrode surfaces. The products of the physical and chemical cleaning reactions are gaseous and are removed by the vacuum pumps.

  15. Enhancing surface functionality of reduced graphene oxide biosensors by oxygen plasma treatment for Alzheimer's disease diagnosis.

    PubMed

    Chae, Myung-Sic; Kim, Jinsik; Jeong, Dahye; Kim, YoungSoo; Roh, Jee Hoon; Lee, Sung Min; Heo, Youhee; Kang, Ji Yoon; Lee, Jeong Hoon; Yoon, Dae Sung; Kim, Tae Geun; Chang, Suk Tai; Hwang, Kyo Seon

    2017-06-15

    We performed oxygen plasma treatment on reduced graphene oxide (rGO) to improve its surface reactivity with respect to biomolecular interactions. Oxygen-plasma-treated rGO surfaces were employed as reactive interfaces for the detection of amyloid-beta (Aβ) peptides, the pathological hallmarks of Alzheimer's disease (AD), as the target analytes. By measuring the changes in electrical characteristics and confirmation through topographic analysis, the oxygen-plasma-treated rGO sensors had enhanced surface functionality for better antibody immobilization and sensing performance, with a 3.33-fold steeper slope for the electrical responses versus analyte concentration curve (logarithmic scale) compared to the untreated. The elicited biomolecular reactivity of the rGO surfaces with the oxygen plasma treatment remained at 46-51% of the initial value even after aging for 6h in ambient conditions. This phenomenon was also confirmed by pretreating the rGO surfaces with a blocking agent and subsequently subjecting them to antibody immobilization. Finally, the feasibility of the oxygen-plasma-treated rGO sensors as a diagnostic tool was evaluated with clinical samples of neural-derived exosomal Aβ peptides extracted from apparent AD patients and normal controls (NC). In contrast to the untreated sensors (p=0.0460), the oxygen-plasma-treated rGO sensors showed a significant p-value in the identification of clinical samples of AD and NC subjects (p<0.001). These results suggest that oxygen plasma treatment improves sensor performance without complicated fabrication procedures and should aid in the development of novel diagnostic tools based on carbon nanomaterials.

  16. Modification of polypropylene foils by low pressure oxygen plasma and its influence on the formation of titanium dioxide films

    NASA Astrophysics Data System (ADS)

    Sadowski, Rafal; Macyk, Wojciech

    2014-10-01

    Commercially available polypropylene foils were pre-treated with low pressure, room temperature radio frequency (RF) oxygen plasma at constant power and pressure. Various durations of pre-treatment process were applied. Afterwards the samples were covered with titanium dioxide thin film by dip-coating technique and photosensitized by titanium(IV) surface complexes formed upon impregnation with catechol-like ligands. Optical emission spectroscopy (OES) measurements were used for determining plasma species. The surface properties before and after plasma treatment were characterized by contact angle measurements, FTIR-ATR, UV-Vis, and X-ray photoelectron spectroscopy (XPS). Titanium dioxide thin films were characterized by scanning electron microscopy (SEM) and UV-Vis spectroscopy. The photoactivity of TiO2 films was tested by photocurrent measurements. It was shown that plasma pre-treatment is essential for oxygen groups formation which contribute to titanium dioxide binding to polymer surface. The support from National Science Centre within the DEC-2012/05/N/ST5/01497 grant is highly acknowledged.

  17. Treatment of enterococcus faecalis bacteria by a helium atmospheric cold plasma brush with oxygen addition

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Huang, Jun; Du, Ning; Liu, Xiao-Di; Wang, Xing-Quan; Lv, Guo-Hua; Zhang, Guo-Ping; Guo, Li-Hong; Yang, Si-Ze

    2012-07-01

    An atmospheric cold plasma brush suitable for large area and low-temperature plasma-based sterilization is designed. Results demonstrate that the He/O2 plasma more effectively kills Enterococcus faecalis than the pure He plasma. In addition, the sterilization efficiency values of the He/O2 plasma depend on the oxygen fraction in Helium gas. The atmospheric cold plasma brush using a proper ratio of He/O2 (2.5%) reaches the optimum sterilization efficiency. After plasma treatment, the cell structure and morphology changes can be observed by the scanning electron microscopy. Optical emission measurements indicate that reactive species such as O and OH play a significant role in the sterilization process.

  18. Treatment of enterococcus faecalis bacteria by a helium atmospheric cold plasma brush with oxygen addition

    SciTech Connect

    Chen Wei; Huang Jun; Wang Xingquan; Lv Guohua; Zhang Guoping; Du Ning; Liu Xiaodi; Guo Lihong; Yang Size

    2012-07-01

    An atmospheric cold plasma brush suitable for large area and low-temperature plasma-based sterilization is designed. Results demonstrate that the He/O{sub 2} plasma more effectively kills Enterococcus faecalis than the pure He plasma. In addition, the sterilization efficiency values of the He/O{sub 2} plasma depend on the oxygen fraction in Helium gas. The atmospheric cold plasma brush using a proper ratio of He/O{sub 2} (2.5%) reaches the optimum sterilization efficiency. After plasma treatment, the cell structure and morphology changes can be observed by the scanning electron microscopy. Optical emission measurements indicate that reactive species such as O and OH play a significant role in the sterilization process.

  19. Real-time frequency-domain fiber optic sensor for intra-arterial blood oxygen measurements

    NASA Astrophysics Data System (ADS)

    Alcala, J. R.; Scott, Ian L.; Parker, Jennifer W.; Atwater, Beauford W.; Yu, Clement; Fischer, Russell; Bellingrath, K.

    1993-05-01

    A real time frequency domain phosphorimeter capable of measuring precise and accurate excited state lifetimes for determining oxygen is described. This frequency domain instrument does not make use of cross correlation techniques traditionally used in frequency domain fluorometers. Instead, the electrical signal from the detector is filtered to contain only the first several harmonics. This filtered signal is then sampled and averaged over a few thousand cycles. The absolute phase and absolute modulation of each sampled harmonic of the excitation and of the luminescence is computed by employing fast Fourier transform algorithms. The phase delay and the modulation ratio is then calculated at each harmonic frequency. A least squares fit is performed in the frequency domain to obtain the lifetimes of discrete exponentials. Oxygen concentrations are computed from these lifetimes. Prototypes based on these techniques were built employing commercially available components. Results from measurements in saline solution and in the arterial blood of dogs show that oxygen concentrations can be determined reproducibly. The system drift is less than 1% in over 100 hours of continuous operation. The performance of fiber optic sensors was evaluated in dogs over a period of 10 hours. The sensors tracked changes in arterial oxygen tension over the course of the experiment without instabilities. The overall response of the system was about 90 seconds. The update time was 3 seconds.

  20. Microbicidal activities of low frequency atmospheric pressure plasma jets on oral pathogens.

    PubMed

    Yamazaki, Hiromitsu; Ohshima, Tomoko; Tsubota, Yuji; Yamaguchi, Hiroyasu; Jayawardena, Jayanetti Asiri; Nishimura, Yasushi

    2011-01-01

    Research using low frequency atmospheric pressure plasma jets (LF jet) is becoming increasingly more common. We carried out experiments to evaluate the sterilizing effects of this technology on oral pathogenic microorganisms (S.mutans, C.albicans and E. faecalis) and to determine its potential for clinical application. We performed the direct exposure test on a solid surface, indirect exposure test on a liquid phase, and ROS (reactive oxygen species) inhibitory test. The results showed the LF jet had microbicidal effects on oral pathogens, and that the ROS influenced this sterilization effect. The experiments of this study revealed that LF jet had a sterilizing effect on oral pathogenic microorganisms present in both the solid and liquid phases. The sterilizing mechanism was considered to be related to the effect of superoxide anion radicals. These results indicate that LF jets may represent a novel technology that can be applied to the field of clinical dentistry.

  1. Influence of oxygen in atmospheric-pressure argon plasma jet on sterilization of Bacillus atrophaeous spores

    NASA Astrophysics Data System (ADS)

    Lim, Jin-Pyo; Uhm, Han S.; Li, Shou-Zhe

    2007-09-01

    A nonequilibrium Ar /O2 plasma discharge at atmospheric pressure was carried out in a coaxial cylindrical reactor with a stepped electrode configuration powered by a 13.56MHz rf power supplier. The argon glow discharge with high electron density produces oxygen reactive species in large quantities. Argon plasma jets penetrate deep into ambient air and create a path for oxygen radicals to sterilize microbes. A sterilization experiment with bacterial endospores indicates that an argon-oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby demonstrating its capability to clean surfaces and its usefulness for reinstating contaminated equipment as free from toxic biological warfare agents. The decimal reduction time (D values) of the Ar /O2 plasma jet at an exposure distance of 0.5-1.5cm ranges from 5 to 57s. An actinometric comparison of the sterilization data shows that atomic oxygen radicals play a significant role in plasma sterilization. When observed under a scanning electron microscope, the average size of the spores appears to be greatly reduced due to chemical reactions with the oxygen radicals.

  2. Influence of oxygen in atmospheric-pressure argon plasma jet on sterilization of Bacillus atrophaeous spores

    SciTech Connect

    Lim, Jin-Pyo; Uhm, Han S.; Li, Shou-Zhe

    2007-09-15

    A nonequilibrium Ar/O{sub 2} plasma discharge at atmospheric pressure was carried out in a coaxial cylindrical reactor with a stepped electrode configuration powered by a 13.56 MHz rf power supplier. The argon glow discharge with high electron density produces oxygen reactive species in large quantities. Argon plasma jets penetrate deep into ambient air and create a path for oxygen radicals to sterilize microbes. A sterilization experiment with bacterial endospores indicates that an argon-oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby demonstrating its capability to clean surfaces and its usefulness for reinstating contaminated equipment as free from toxic biological warfare agents. The decimal reduction time (D values) of the Ar/O{sub 2} plasma jet at an exposure distance of 0.5-1.5 cm ranges from 5 to 57 s. An actinometric comparison of the sterilization data shows that atomic oxygen radicals play a significant role in plasma sterilization. When observed under a scanning electron microscope, the average size of the spores appears to be greatly reduced due to chemical reactions with the oxygen radicals.

  3. Oxygen transport in the internal xenon plasma of a dispenser hollow cathode

    SciTech Connect

    Capece, Angela M. Shepherd, Joseph E.; Polk, James E.; Mikellides, Ioannis G.

    2014-04-21

    Reactive gases such as oxygen and water vapor modify the surface morphology of BaO dispenser cathodes and degrade the electron emission properties. For vacuum cathodes operating at fixed temperature, the emission current drops rapidly when oxygen adsorbs on top of the low work function surface. Previous experiments have shown that plasma cathodes are more resistant to oxygen poisoning and can operate with O{sub 2} partial pressures one to two orders of magnitude higher than vacuum cathodes before the onset of poisoning occurs. Plasma cathodes used for electric thrusters are typically operated with xenon; however, gas phase barium, oxygen, and tungsten species may be found in small concentrations. The densities of these minor species are small compared with the plasma density, and thus, their presence in the discharge does not significantly alter the xenon plasma parameters. It is important, however, to consider the transport of these minor species as they may deposit on the emitter surface and affect the electron emission properties. In this work, we present the results of a material transport model used to predict oxygen fluxes to the cathode surface by solving the species conservation equations in a cathode with a 2.25 mm diameter orifice operated at a discharge current of 15 A, a Xe flow rate of 3.7 sccm, and 100 ppm of O{sub 2}. The dominant ionization process for O{sub 2} is resonant charge exchange with xenon ions. Ba is effectively recycled in the plasma; however, BaO and O{sub 2} are not. The model shows that the oxygen flux to the surface is not diffusion-limited; therefore, the high resistance to oxygen poisoning observed in plasma cathodes likely results from surface processes not considered here.

  4. Measuring atomic oxygen densities and electron properties in an Inductively Coupled Plasma for thin film deposition

    NASA Astrophysics Data System (ADS)

    Meehan, David; Gibson, Andrew; Booth, Jean-Paul; Wagenaars, Erik

    2016-09-01

    Plasma Enhanced Pulsed Laser Deposition (PE-PLD) is an advanced way of depositing thin films of oxide materials by using a laser to ablate a target, and passing the resulting plasma plume through a background Inductively-Coupled Plasma (ICP), instead of a background gas as is done in traditional PLD. The main advantage of PE-PLD is the control of film stoichiometry via the direct control of the reactive oxygen species in the ICP instead of relying on a neutral gas background. The aim is to deposit zinc oxide films from a zinc metal target and an oxygen ICP. In this work, we characterise the range of compositions of the reactive oxygen species achievable in ICPs; in particular the atomic oxygen density. The density of atomic oxygen has been determined within two ICPs of two different geometries over a range of plasma powers and pressures with the use of Energy Resolved Actinometry (ERA). ERA is a robust diagnostic technique with determines both the dissociation degree and average electron energy by comparing the excitation ratios of two oxygen and one argon transition. Alongside this the electron densities have been determined with the use of a hairpin probe. This work received financial support from the EPSRC, and York-Paris CIRC.

  5. Ion cyclotron range of frequencies heating of plasma with small impurity production

    DOEpatents

    Ohkawa, Tihiro

    1987-01-01

    Plasma including plasma ions is magnetically confined by a magnetic field. The plasma has a defined outer surface and is intersected by resonance surfaces of respective common ion cyclotron frequency of a predetermined species of plasma ions moving in the magnetic field. A radio frequency source provides radio frequency power at a radio frequency corresponding to the ion cyclotron frequency of the predetermined species of plasma ions moving in the field at a respective said resonance surface. RF launchers coupled to the radio frequency source radiate radio frequency energy at the resonance frequency onto the respective resonance surface within the plasma from a plurality of locations located outside the plasma at such respective distances from the intersections of the respective resonance surface and the defined outer surface and at such relative phases that the resulting interference pattern provides substantially null net radio frequency energy over regions near and including substantial portions of the intersections relative to the radio frequency energy provided thereby at other portions of the respective resonance surface within the plasma.

  6. Assessment of plasma impedance probe for measuring electron density and collision frequency in a plasma with spatial and temporal gradients

    SciTech Connect

    Hopkins, Mark A. King, Lyon B.

    2014-05-15

    Numerical simulations and experimental measurements were combined to determine the ability of a plasma impedance probe (PIP) to measure plasma density and electron collision frequency in a plasma containing spatial gradients as well as time-varying oscillations in the plasma density. A PIP is sensitive to collision frequency through the width of the parallel resonance in the Re[Z]-vs.-frequency characteristic, while also being sensitive to electron density through the zero-crossing of the Im[Z]-vs.-frequency characteristic at parallel resonance. Simulations of the probe characteristic in a linear plasma gradient indicated that the broadening of Re[Z] due to the spatial gradient obscured the broadening due to electron collision frequency, preventing a quantitative measurement of the absolute collision frequency for gradients considered in this study. Simulation results also showed that the PIP is sensitive to relative changes in electron collision frequency in a spatial density gradient, but a second broadening effect due to time-varying oscillations made collision frequency measurements impossible. The time-varying oscillations had the effect of causing multiple zero-crossings in Im[Z] at parallel resonance. Results of experiments and simulations indicated that the lowest-frequency zero-crossing represented the lowest plasma density in the oscillations and the highest-frequency zero-crossing represented the highest plasma density in the oscillations, thus the PIP probe was found to be an effective tool to measure both the average plasma density as well as the maximum and minimum densities due to temporal oscillations.

  7. Synergistic effect of EUV from the laser-sustained detonation plasma in a ground-based atomic oxygen simulation on fluorinated polymers

    SciTech Connect

    Tagawa, Masahito; Abe, Shingo; Kishida, Kazuhiro; Yokota, Kumiko; Okamoto, Akio

    2009-01-05

    The contribution of extreme ultraviolet (EUV) from a laser-sustained plasma on the mass loss phenomenon of fluorinated polymer in a ground-based laser-detonation atomic oxygen beam source was evaluated. The atomic oxygen beam and EUV from the oxygen plasma were separated by the high-speed chopper wheel installed in the beam source. The mass changes of the fluorinated polymer and polyimide were measured from the frequency shift of the quartz crystal microbalance during the beam exposures. It has been made clear that the fluorinated polymer erodes by EUV exposure alone. In contrast, no erosion was detected for polyimide by EUV alone. The atomic oxygen-induced erosion was measured for both materials even without EUV exposure. However, no strong synergistic effect was observed for a fluorinated polymer even under the simultaneous exposure condition of atomic oxygen and EUV. Similar results were observed even in simultaneous exposure of atomic oxygen (without EUV) and 172 nm vacuum ultraviolet (VUV) from an excimer lamp. These experiments suggest that the primary origin of the accelerated erosion of fluorinated polymer observed in a laser detonation atomic oxygen source is not the EUV from the laser-sustained plasma.

  8. Computational study of sheath structure in oxygen containing plasmas at medium pressures

    NASA Astrophysics Data System (ADS)

    Hrach, Rudolf; Novak, Stanislav; Ibehej, Tomas; Hrachova, Vera

    2016-09-01

    Plasma mixtures containing active species are used in many plasma-assisted material treatment technologies. The analysis of such systems is rather difficult, as both physical and chemical processes affect plasma properties. A combination of experimental and computational approaches is the best suited, especially at higher pressures and/or in chemically active plasmas. The first part of our study of argon-oxygen mixtures was based on experimental results obtained in the positive column of DC glow discharge. The plasma was analysed by the macroscopic kinetic approach which is based on the set of chemical reactions in the discharge. The result of this model is a time evolution of the number densities of each species. In the second part of contribution the detailed analysis of processes taking place during the interaction of oxygen containing plasma with immersed substrates was performed, the results of the first model being the input parameters. The used method was the particle simulation technique applied to multicomponent plasma. The sheath structure and fluxes of charged particles to substrates were analysed in the dependence on plasma pressure, plasma composition and surface geometry.

  9. Differentiating the role of lithium and oxygen in retaining deuterium on lithiated plasma-facing components

    NASA Astrophysics Data System (ADS)

    Taylor, Chase

    2013-10-01

    Lithium wall conditioning has been implemented in nearly a dozen fusion devices, resulting in significantly improved plasma performance. Improvements are manifest as a reduction and eventual elimination of edge localized modes, reduced edge neutral density, reduced deuterium recycling, and some reduction in impurities. Initially, researchers assumed that lithium, via a direct lithium-deuterium bond, was directly responsible for these improvements. Our experiments and atomistic simulations have revealed that lithium coatings play a much more indirect role in improving plasma performance. The presence of oxygen in tokamaks is ubiquitously viewed as unfavorable. However, recent results show that lithium reduces oxygen impurities and surprisingly uses the oxygen to retain deuterium. Experiments using X-ray photoelectron spectroscopy identify that oxygen immediately begins to accumulate on lithium conditioned surfaces. Tight-binding density functional theory simulations tested various carbon matrices with and without lithium, oxygen, and hydrogen, and identified that oxygen plays the key role in retaining deuterium. In fact, a simulated PFC with 20% oxygen in carbon retains more deuterium than does 20% lithium in carbon. Recent experiments implanted oxygen in graphite to match simulations; however, we were unable to achieve the simulated results because all implanted oxygen was released upon deuterium bombardment. We therefore conclude that while oxygen retains deuterium, lithium plays an indispensible role in this process. Lithium attracts and retains oxygen, and then oxygen binds and retains deuterium. Work supported by USDOE Contracts DE-FG02-08ER54990 and DOE ID Field Office contract DE-AC07-05ID14517.

  10. The effect of oxygen-plasma treatment on the mechanical and piezoelectrical properties of ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Hussain, Mushtaque; Khan, Azam; Nur, Omer; Willander, Magnus; Broitman, Esteban

    2014-07-01

    We have studied the effect of oxygen plasma treatment on piezoelectric response and on the mechanical stability of ZnO nanorods synthesized on FTO by using ACG method. XRD and SEM techniques have shown highly dense and uniformly distributed nanorods. The piezoelectric properties and mechanical stability of as-grown and oxygen plasma treated samples were investigated by using nanoindentation technique. The comparison of load-displacement curves showed that the oxygen plasma treated samples are much stiffer and show higher generated piezo-voltage. This study demonstrates that the oxygen-plasma treatment is a good option to fabricate reliable and efficient nanodevices for enhanced generation of piezoelectricity.

  11. Cold plasma processing of local planetary ores for oxygen and metallurgically important metals

    NASA Technical Reports Server (NTRS)

    Lynch, D. C.; Bullard, D.; Ortega, R.

    1990-01-01

    The utilization of a cold plasma in chlorination processing is described. Essential equipment and instruments were received, the experimental apparatus assembled and tested, and preliminary experiments conducted. The results of the latter lend support to the original hypothesis: a cold plasma can both significantly enhance and bias chemical reactions. In two separate experiments, a cold plasma was used to reduce TiCl4 vapor and chlorinate ilmenite. The latter, reacted in an argon-chlorine plasma, yielded oxygen. The former experiment reveals that chlorine can be recovered as HCl vapor from metal chlorides in a hydrogen plasma. Furthermore, the success of the hydrogen experiments has lead to an analysis of the feasibility of direct hydrogen reduction of metal oxides in a cold plasma. That process would produce water vapor and numerous metal by-products.

  12. Method for determining the effects of oxygen plasma on a specimen

    NASA Technical Reports Server (NTRS)

    Whitaker, Ann F. (Inventor)

    1991-01-01

    A method for determining the effects of exposure of oxygen plasma on a specimen such as a thin film polymer or thin metals. The method includes providing an apparatus with a chamber having a holder supporting the polymer specimen in a plasma environment provided in the chamber. The chamber is regulated to a predetermined pressure and set temperature prior to the introduction of oxygen plasma therein. The specimen is then subjected to the plasma environment for a predetermined time during which time the temperature of the specimen is sensed and regulated to be maintained at the set temperature. Temperature sensing is accomplished by a probe which senses any changes in bulk sample temperature. Temperature regulation is provided by a thermoelectric module and by a coolant flow tube.

  13. Surface characterization and adhesion of oxygen plasma-modified LARC-TPI

    NASA Technical Reports Server (NTRS)

    Chin, J. W.; Wightman, J. P.

    1992-01-01

    LARC-TPI, an aromatic thermoplastic polyimide, was exposed to an oxygen plasma as a surface pretreatment for adhesive bonding. Chemical and physical changes which occurred in the polyimide surface as a result of the plasma treatment were investigated using X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IR-RAS), contact-angle analysis, ellipsometry, and high resolution SEM. A 180-deg peel test with an acrylate-based pressure sensitive adhesive as a flexible adherent was utilized to study the interactions of the plasma-treated polyimide surface with other polymeric materials. The surface characterization and adhesion testing results showed that the oxygen plasma treatment, while creating a more hydrophilic, polar surface, also caused chain scission, resulting in the formation of a weak boundary layer which inhibited adhesion.

  14. Optimizing the synthesis of vanadium-oxygen nanostructures by plasma plume dynamics using optical imaging

    NASA Astrophysics Data System (ADS)

    Masina, Bathusile N.; Lafane, Slimane; Wu, Lorinda; Abdelli-Messaci, Samira; Kerdja, Tahar; Forbes, Andrew

    2015-03-01

    The effect of an oxygen atmosphere on the expansion dynamics of a laser-produced vanadium-oxygen plasma has been investigated using a fast intensified charged-coupled device camera. We find regimes of the plasma plume expansion ranging from a free plume at vacuum and low oxygen pressures, through collisional and shock-wave-like hydrodynamic regimes at intermediate oxygen pressure, finally reaching a confined plume with subsequent thermalization of the plume particles at the highest pressure of the oxygen gas. Vanadium oxide nanostructures thin films were synthesized from this plasma and the resulting vanadium oxide phases studied as a function of the plume dynamics. We found monoclinic vanadium dioxide (VO2) (M1) and VO2 (B) nanoparticles in thin films deposited at 0.05 mbar. Pure phases of vanadium trioxide (V2O3) smooth and pentoxide (V2O5) nanorods thin films were detected at 0.01 and 0.1 to 0.2 mbar, respectively. Thin films containing VO2 (M1) were found to have a reversible metal-to-insulator transition at 61°C. This work paves the way to VO phase control by judicious choice of laser and plasma conditions.

  15. Analysis of EUV Oxygen Spectra from LLNL SSPX and UNR Laser Plasma Source of ``Sparky''

    NASA Astrophysics Data System (ADS)

    Wilcox, P. G.; Safronova, A. S.; Kantsyrev, V. L.; Safronova, U. I.; Williamson, K. M.; Weller, M. E.; Clementson, J.; Beiersdorfer, P.; Struve, K. W.

    2008-11-01

    In our recent work [Wilcox et al, RSI (2008, in press)] we applied a non- LTE kinetic model of oxygen to analyze an oxygen spectrum between 140 and 240 å, produced on LLNL SSPX. Here we study the whole collection of recent experimental SSPX EUV oxygen spectra produced under different plasma conditions, specifically in the broad range of temperatures from as low as 15 eV up to 280 eV, and at an electron density of around 10 ^14 cm-3. In addition, we analyze new experimental data from EUV oxygen and carbon spectra, recorded at much higher density at the compact laser plasma source of ``Sparky'' at UNR . The comprehensive comparison of EUV oxygen spectra from both experiments with theoretical calculations was accomplished, and temperature and density sensitive lines were identified.This work is relevant to diagnostics of plasma with low -- Z ions and Tokamak plasma in particular. Work is supported by DOE under grant DE-FG02-08ER54951 and in part under NNSA Coop. Agr. DE-FC52-06NA27588 and DE-FC52-06NA27586. Work at LLNL was performed under auspices of the DOE under contract DE-AC52-07NA2344.

  16. Deposition of Lanthanum Strontium Cobalt Ferrite (LSCF) Using Suspension Plasma Spraying for Oxygen Transport Membrane Applications

    NASA Astrophysics Data System (ADS)

    Fan, E. S. C.; Kesler, O.

    2015-08-01

    Suspension plasma spray deposition was utilized to fabricate dense lanthanum strontium cobalt ferrite oxygen separation membranes (OSMs) on porous metal substrates for mechanical support. The as-sprayed membranes had negligible and/or reversible material decomposition. At the longer stand-off distance (80 mm), smooth and dense membranes could be manufactured using a plasma with power below approximately 81 kW. Moreover, a membrane of 55 μm was observed to have very low gas leakage rates desirable for OSM applications. This thickness could potentially be decreased further to improve oxygen diffusion by using metal substrates with finer surface pores.

  17. Sterilization of Bacillus subtilis Spores Using an Atmospheric Plasma Jet with Argon and Oxygen Mixture Gas

    NASA Astrophysics Data System (ADS)

    Shen, Jie; Cheng, Cheng; Fang, Shidong; Xie, Hongbing; Lan, Yan; Ni, Guohua; Meng, Yuedong; Luo, Jiarong; Wang, Xiangke

    2012-03-01

    To determine an efficient sterilization mechanism, Bacillus subtilis spore samples were exposed to an atmospheric plasma jet. By using argon/oxygen mixture gas, the decimal reduction value was reduced from 60 s (using argon gas) to 10 s. More dramatically, after 5 min treatment, the colony-forming unit (CFU) was reduced by six orders. To understand the underlying mechanism of the efficient sterilization by plasma, the contributions from heat, UV radiation, charged particles, ozone, and reactive oxygen radicals were distinguished in this work, showing that charged particles and ozone were the main killing factors. The shape changes of the spores were also discussed.

  18. Plasma turbulence measured with fast frequency swept reflectometry in JET H-mode plasmas

    NASA Astrophysics Data System (ADS)

    Clairet, F.; Sirinelli, A.; Meneses, L.; Contributors, JET

    2016-12-01

    In this work we present recent achievements to provide precise measurements of turbulence on JET H-mode plasmas using frequency sweeping reflectometry diagnostic. The plasma density fluctuations retrieved from swept reflected signals, first initiated with the Tore Supra reflectometry (Heuraux et al 2003 Rev. Sci. Instrum. 74 1501, Vermare et al 2006 Nucl. Fusion 46 S743, Gerbaud et al 2006 Rev. Sci. Instrum. 77 10E928), provides a radial profile of the density fluctuation level and its spectral structure. Using the complete set of the JET X-mode fast sweeping heterodyne reflectometers we have determined the temporal dynamic of the density fluctuation profile from the edge to the center during an H-mode discharge. At the L-H transition, the turbulence reduction seems to occur, at first, simultaneously from the edge to the center then deepens at the edge at ρ ~ 0.95 and this deepening propagates toward the center with a steepening of the wavenumber spectra. During an edge localized mode (ELM) event, a substantial density fluctuations increase has been observed with a localized turbulent wave front propagating toward the center accompanying a particle transport. We also show that type-III ELMs sustain a steady and high level of plasma turbulence compare to type-I.

  19. Charge neutral MoS2 field effect transistors through oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Dhall, Rohan; Li, Zhen; Kosmowska, Ewa; Cronin, Stephen B.

    2016-11-01

    Lithographically fabricated MoS2 field effect transistors suffer from several critical imperfections, including low sub-threshold swings, large turn-on gate voltages (VT), and wide device-to-device variability. The large magnitude and variability of VT stems from unclean interfaces, trapped charges in the underlying substrate, and sulfur vacancies created during the mechanical exfoliation process. In this study, we demonstrate a simple and reliable oxygen plasma treatment, which mitigates the effects of unintentional doping created by surface defect sites, such as S vacancies, and surface contamination. This plasma treatment restores charge neutrality to the MoS2 and shifts the threshold turn-on voltage towards 0 V. Out of the 10 devices measured, all exhibit a shift of the FET turn-on voltage from an average of -18 V to -2 V. The oxygen plasma treatment passivates these defects, which reduces surface scattering, causing increased mobility and improved subthreshold swing. For as-prepared devices with low mobilities (˜0.01 cm2/V s), we observe up to a 190-fold increase in mobility after exposure to the oxygen plasma. Perhaps the most important aspect of this oxygen plasma treatment is that it reduces the device-to-device variability, which is a crucial factor in realizing any practical application of these devices.

  20. First-in-human pilot study of a spatial frequency domain oxygenation imaging system

    NASA Astrophysics Data System (ADS)

    Gioux, Sylvain; Mazhar, Amaan; Lee, Bernard T.; Lin, Samuel J.; Tobias, Adam M.; Cuccia, David J.; Stockdale, Alan; Oketokoun, Rafiou; Ashitate, Yoshitomo; Kelly, Edward; Weinmann, Maxwell; Durr, Nicholas J.; Moffitt, Lorissa A.; Durkin, Anthony J.; Tromberg, Bruce J.; Frangioni, John V.

    2011-08-01

    Oxygenation measurements are widely used in patient care. However, most clinically available instruments currently consist of contact probes that only provide global monitoring of the patient (e.g., pulse oximetry probes) or local monitoring of small areas (e.g., spectroscopy-based probes). Visualization of oxygenation over large areas of tissue, without a priori knowledge of the location of defects, has the potential to improve patient management in many surgical and critical care applications. In this study, we present a clinically compatible multispectral spatial frequency domain imaging (SFDI) system optimized for surgical oxygenation imaging. This system was used to image tissue oxygenation over a large area (16×12 cm) and was validated during preclinical studies by comparing results obtained with an FDA-approved clinical oxygenation probe. Skin flap, bowel, and liver vascular occlusion experiments were performed on Yorkshire pigs and demonstrated that over the course of the experiment, relative changes in oxygen saturation measured using SFDI had an accuracy within 10% of those made using the FDA-approved device. Finally, the new SFDI system was translated to the clinic in a first-in-human pilot study that imaged skin flap oxygenation during reconstructive breast surgery. Overall, this study lays the foundation for clinical translation of endogenous contrast imaging using SFDI.

  1. Nightmares and oxygen desaturations: is sleep apnea related to heightened nightmare frequency?

    PubMed

    Schredl, Michael; Schmitt, Judith; Hein, Gerhard; Schmoll, Tina; Eller, Sabine; Haaf, Janina

    2006-12-01

    In the 19th century, several authors held the view that nightmares are caused by oxygen shortage. The present study was designed to study nightmare frequency in patients with obstructive sleep apnea syndrome and its relationship to respiratory parameters. A brief questionnaire was administered to 323 patients with sleep apnea syndrome before their first laboratory night. The reduction in nightmare frequency in the sleep apnea group was explained by the reduced dream recall frequency. Despite some illustrative examples of a correlation between oxygen desaturation and dream content, the respiratory parameters as measures of sleep apnea syndrome severity did not correlate substantially with nightmare frequency. Psychiatric comorbidity and an intake of psychotropic medication were associated with heightened nightmare frequency in this sample. It must be concluded that the oxygen hypothesis did not play a major role in explaining the occurrence of nightmares. As this might be partly explained by adaptation to the nightly desaturation periods, it will be fruitful to apply experimental procedures that interrupt airflow during (rapid eye movement) REM sleep for short periods in a systematic way without the knowledge of the sleeper and to then study their effects on dream content. Some patients reported a correlation between daytime stressors and nightmares, which is in line with modern etiological models of nightmares.

  2. Method for minimizing decarburization and other high temperature oxygen reactions in a plasma sprayed material

    DOEpatents

    Lenling, William J.; Henfling, Joseph A.; Smith, Mark F.

    1993-06-08

    A method is disclosed for spray coating material which employs a plasma gun that has a cathode, an anode, an arc gas inlet, a first powder injection port, and a second powder injection port. A suitable arc gas is introduced through the arc gas inlet, and ionization of the arc gas between the cathode and the anode forms a plasma. The plasma is directed to emenate from an open-ended chamber defined by the boundary of the anode. A coating is deposited upon a base metal part by suspending a binder powder within a carrier gas that is fed into the plasma through the first powder injection port; a material subject to degradation by high temperature oxygen reactions is suspended within a carrier gas that is fed into the plasma through the second injection port. The material fed through the second injection port experiences a cooler portion of the plasma and has a shorter dwell time within the plasma to minimize high temperature oxygen reactions. The material of the first port and the material of the second port intermingle within the plasma to form a uniform coating having constituent percentages related to the powder-feed rates of the materials through the respective ports.

  3. Radio frequency energy coupling to high-pressure optically pumped nonequilibrium plasmas

    NASA Astrophysics Data System (ADS)

    Plönjes, Elke; Palm, Peter; Lee, Wonchul; Lempert, Walter R.; Adamovich, Igor V.

    2001-06-01

    This article presents an experimental demonstration of a high-pressure unconditionally stable nonequilibrium molecular plasma sustained by a combination of a continuous wave CO laser and a sub-breakdown radio frequency (rf) electric field. The plasma is sustained in a CO/N2 mixture containing trace amounts of NO or O2 at pressures of P=0.4-1.2 atm. The initial ionization of the gases is produced by an associative ionization mechanism in collisions of two CO molecules excited to high vibrational levels by resonance absorption of the CO laser radiation with subsequent vibration-vibration (V-V) pumping. Further vibrational excitation of both CO and N2 is produced by free electrons heated by the applied rf field, which in turn produces additional ionization of these species by the associative ionization mechanism. In the present experiments, the reduced electric field, E/N, is sufficiently low to preclude field-induced electron impact ionization. Unconditional stability of the resultant cold molecular plasma is enabled by the negative feedback between gas heating and the associative ionization rate. Trace amounts of nitric oxide or oxygen added to the baseline CO/N2 gas mixture considerably reduce the electron-ion dissociative recombination rate and thereby significantly increase the initial electron density. This allows triggering of the rf power coupling to the vibrational energy modes of the gas mixture. Vibrational level populations of CO and N2 are monitored by infrared emission spectroscopy and spontaneous Raman spectroscopy. The experiments demonstrate that the use of a sub-breakdown rf field in addition to the CO laser allows an increase of the plasma volume by about an order of magnitude. Also, CO infrared emission spectra show that with the rf voltage turned on the number of vibrationally excited CO molecules along the line of sight increase by a factor of 3-7. Finally, spontaneous Raman spectra of N2 show that with the rf voltage the vibrational temperature

  4. Method and apparatus for upshifting light frequency by rapid plasma creation

    DOEpatents

    Dawson, John M.; Wilks, Scott C.; Mori, Warren B.; Joshi, Chandrasekhar J.; Sessler, Andrew M.

    1990-01-01

    Photons of an electromagnetic source wave are frequency-upshifted as a plasma is rapidly created around the path of this propagating source wave. The final frequency can be controlled by adjusting the gas density. A controlled time-varying frequency (chirped) pulse can be produced by using a controlled spatially varying gas density. The plasma must be created in a time which is short compared to the transit time of the light through the plasmas region. For very fast creation over one to at most a few light periods of an overdense plasma, static magnetic fields with short wavelengths are created.

  5. Characterization of an oxygen plasma process for cleaning packaged semiconductor devices. Final report

    SciTech Connect

    Adams, B.E.

    1996-11-01

    The purpose of this research was to experimentally determine the operating {open_quotes}window{close_quotes} for an oxygen plasma cleaning process to be used on microelectronics components just prior to wire bonding. The process was being developed to replace one that used vapor degreasing with trichlorotrifluoroethane, an ozone-depleting substance. A Box-Behnken experimental design was used to generate data from which the oxygen plasma cleaning process could be characterized. Auger electron spectrophotometry was used to measure the contamination thickness on the dice after cleaning. An empirical equation correlating the contamination thickness on the die surface with the operating parameters of the plasma system was developed from the collected Auger data, and optimum settings for cleaning semiconductor devices were determined. Devices were also tested for undesirable changes in electrical parameters resulting from cleaning in the plasma system. An increase in leakage current occurred for bipolar transistors and diodes after exposure to the oxygen plasma. Although an increase in leakage current occurred, each device`s parameter remained well below the acceptable specification limit. Based upon the experimental results, the optimum settings for the plasma cleaning process were determined to be 200 watts of power applied for five minutes in an enclosure maintained at 0.7 torr. At these settings, all measurable contamination was removed without compromising the reliability of the devices.

  6. Is the mammalian cell plasma membrane a barrier to oxygen transport?

    PubMed Central

    1992-01-01

    Oxygen transport in the Chinese hamster ovary (CHO) plasma membrane has been studied by observing the collision of molecular oxygen with nitroxide radical spin labels placed in the lipid bilayer portion of the membrane at various distances from the membrane surface using the long-pulse saturation-recovery electron spin resonance (ESR) technique. The collision rate was estimated for 5-, 12-, and 16-doxylstearic acids from spin-lattice relaxation times (T1) measured in the presence and absence of molecular oxygen. Profiles of the local oxygen transport parameters across the membrane were obtained showing that the oxygen diffusion-concentration product is lower than in water for all locations at 37 degrees C. From oxygen transport parameter profiles, the membrane oxygen permeability coefficients were estimated according to the procedure developed earlier by Subczynski et al. (Subczynski, W. K., J. S. Hyde, and A. Kusumi. 1989. Proceedings of the National Academy of Sciences, USA. 86:4474-4478). At 37 degrees C, the oxygen permeability coefficient for the plasma membrane was found to be 42 cm/s, about two times lower than for a water layer of the same thickness as the membrane. The oxygen concentration difference across the CHO plasma membrane at physiological conditions is in the nanomolar range. It is concluded that oxygen permeation across the cell plasma membrane cannot be a rate-limiting step for cellular respiration. Correlations of the form PM = cKs between membrane permeabilities PM of small nonelectrolyte solutes of mol wt less than 50, including oxygen, and their partition coefficients K into hexadecane and olive oil are reported. Hexadecane: c = 26 cm/s, s = 0.95; olive oil: c = 23 cm/s, s = 1.56. These values of c and s differ from those reported in the literature for solutes of 50 less than mol wt less than 300 (Walter, A., and J. Gutknecht. 1986. Journal of Membrane Biology. 90:207-217). It is concluded that oxygen permeability through membranes can be

  7. Low Frequency Plasma Turbulence as a Source of Clutter in Surveillance and Communication

    DTIC Science & Technology

    2012-09-01

    shear, whereas interchange or flute type oscillations in magnetized plasma are associated with Rayleigh-Taylor type instability. These types of density...density irregularities are excited by plasma flows with velocity shear, whereas interchange or flute type oscillations in magnetized plasma are...equations will be used to describe low-frequency interchange modes ( ,i   where  is the frequency of the flute mode and 0zi i ZeB m c  is the

  8. Oxygen plasma damage to blanket and patterned ultralow-{kappa} surfaces

    SciTech Connect

    Bao, J.; Shi, H.; Huang, H.; Ho, P. S.; McSwiney, M. L.; Goodner, M. D.; Moinpour, M.; Kloster, G. M.

    2010-03-15

    Oxygen plasma damage to blanket and patterned ultralow-{kappa} (ULK) dielectric surfaces was investigated by examining the effect of plasma species and dielectric materials. Blanket ULK films and patterned structures were treated by O{sub 2} plasma in a remote plasma chamber where the ions and radicals from the plasma source can be separately controlled to study their respective roles in the damage process. The plasma damage was characterized by angle resolved x-ray photoelectron spectroscopy, x-ray reflectivity, and Fourier transform infrared spectroscopy. Studies of the angle dependence of oxygen plasma damage to blanket ULK films indicated that damage by ions was anisotropic while that by radicals was isotropic. Ions were found to play an important role in assisting carbon depletion by oxygen radicals on the blanket film surface. More plasma damage was observed with increasing porosity in ultralow-{kappa} films. Probable reaction paths were proposed by analyzing the reaction by-products. Plasma damage to the sidewall of low-{kappa} trenches was examined by electron energy loss (EELS) analysis. The depletion depth of carbon was found to be related to the penetration of radical species into the porous dielectric and the distribution at the sidewall and trench bottom was affected by the trench pattern geometry, i.e., the aspect ratio, which can be correlated with the electron potential distribution and subsequent trajectory of ions. Vapor silylation was applied for dielectric recovery of trench structure and the result was examined by EELS. The trimethylchlorosilane was found to be effective for recovery of the sidewall carbon loss. The recovery was better for loss induced by radical O{sub 2} than by hybrid O{sub 2} and the difference was attributed to the surface densification by ions limiting the mass transport of vapor chemicals.

  9. Power dependence of terahertz carrier frequency in a plasma-based two-color generation process

    NASA Astrophysics Data System (ADS)

    Zhao, Ji; Zhang, Liang-Liang; Luo, Yi-Man; Wu, Tong; Zhang, Cun-Lin; Zhao, Yue-Jin

    2014-12-01

    We conduct a frequency spectrum experiment to investigate terahertz (THz) emissions from laser-induced air plasma under different laser incident powers. The frequency spectra are measured using both air-biased-coherent detection and a Michelson interferometer. The red-shift of the THz pulse carrier frequency is observed as a response to increased pump power. These phenomena are related to plasma collisions and can be explained by the plasma collision model. Based on these findings, it is apparent that the tuning of the THz carrier frequency can be achieved through regulation of the pump beam.

  10. Oxygen plasma-treated thermoresponsive polymer surfaces for cell sheet engineering.

    PubMed

    Shimizu, Kazunori; Fujita, Hideaki; Nagamori, Eiji

    2010-06-01

    Although cell sheet tissue engineering is a potent and promising method for tissue engineering, an increase of mechanical strength of a cell sheet is needed for easy manipulation of it during transplantation or 3D tissue fabrication. Previously, we developed a cell sheet-polymer film complex that had enough mechanical strength that can be manipulated even by tweezers (Fujita et al., 2009. Biotechnol Bioeng 103(2): 370-377). We confirmed the polymer film involving a temperature sensitive polymer and extracellular matrix (ECM) proteins could be removed by lowering temperature after transplantation, and its potential use in regenerative medicine was demonstrated. However, the use of ECM proteins conflicted with high stability in long-term storage and low cost. In the present study, to overcome these drawbacks, we employed the oxygen plasma treatment instead of using the ECM proteins. A cast and dried film of thermoresponsive poly-N-isopropylacrylamide (PNIPAAm) was fabricated and treated with high-intensity oxygen plasma. The cells became possible to adhere to the oxygen plasma-treated PNIPAAm surface, whereas could not to the inherent surface of bulk PNIPAAm without treatment. Characterizations of the treated surface revealed the surface had high stability. The surface roughness, wettability, and composition were changed, depending on the plasma intensity. Interestingly, although bulk PNIPAAm layer had thermoresponsiveness and dissolved below lower critical solution temperature (LCST), it was found that the oxygen plasma-treated PNIPAAm surface lost its thermoresponsiveness and remained insoluble in water below LCST as a thin layer. Skeletal muscle C2C12 cells could be cultured on the oxygen plasma-treated PNIPAAm surface, a skeletal muscle cell sheet with the insoluble thin layer could be released in the medium, and thus the possibility of use of the cell sheet for transplantation was demonstrated.

  11. Propagation of terahertz electromagnetic waves in a magnetized plasma with inhomogeneous electron density and collision frequency

    NASA Astrophysics Data System (ADS)

    Guo, LinJing; Guo, LiXin; Li, JiangTing

    2017-02-01

    This study theoretically analyzes the propagation properties of terahertz (THz) electromagnetic waves in a magnetized plasma that is inhomogeneous in both collision frequency and electron density. Three parabolic profiles are adopted to describe the inhomogeneity of these two parameters in the plasma slab. Numerical calculation results show that when a magnetic field is applied, an absorption valley appears near the middle of the absorption peak. The characteristics of the absorption spectra are affected by two factors: (1) the parameters in the plasma's first layer, which is the border between the air and the plasma and (2) the gradient of the parameters across the entire plasma. Specifically, a more substantial difference between the inhomogeneous plasma and the uniform plasma corresponds to a greater difference between the two absorption spectra. In addition, electron density, plasma thickness, and collision frequency also play important roles in the propagation.

  12. Changes in oxygen saturation and heart frequency during sleep in young normal subjects.

    PubMed Central

    Gimeno, F; Peset, R

    1984-01-01

    Changes in oxygen saturation and heart frequency were measured during sleep in a group of 21 normal subjects (9 women and 12 men) aged 19-25. At the time of the investigation all were non-smokers, they had no respiratory complaints, and indices of lung function (lung volumes, volume-pressure diagram, and diffusing capacity for carbon monoxide) were within normal limits. In contrast to published data, there were no major changes in oxygen saturation and no differences between men and women. PMID:6474401

  13. Synthesis of ferrite and nickel ferrite nanoparticles using radio-frequency thermal plasma torch

    NASA Astrophysics Data System (ADS)

    Son, S.; Taheri, M.; Carpenter, E.; Harris, V. G.; McHenry, M. E.

    2002-05-01

    Nanocrystalline (NC) ferrite powders have been synthesized using a 50 kW-3 MHz rf thermal plasma torch for high-frequency soft magnet applications. A mixed powder of Ni and Fe (Ni:Fe=1:2), a NiFe permalloy powder with additional Fe powder (Ni:Fe=1:2), and a NiFe permalloy powder (Ni:Fe=1:1) were used as precursors for synthesis. Airflow into the reactor chamber was the source of oxygen for oxide formation. XRD patterns clearly show that the precursor powders were transformed into NC ferrite particles with an average particle size of 20-30 nm. SEM and TEM studies indicated that NC ferrite particles had well-defined polygonal growth forms with some exhibiting (111) faceting and many with truncated octahedral and truncated cubic shapes. The Ni content in the ferrite particles was observed to increase in going from mixed Ni and Fe to mixed permalloy and iron and finally to only permalloy starting precursor. The plasma-torch synthesized ferrite materials using exclusively the NiFe permalloy precursor had 40%-48% Ni content in the Ni-ferrite particle, differing from the NiFe2O4 ideal stoichiometry. EXAFS was used to probe the cation coordination in low Ni magnetite species. The coercivity and Neel temperature of the high Ni content ferrite sample were 58 Oe and ˜590 °C, respectively.

  14. Collisionless expansion of pulsed radio frequency plasmas. II. Parameter study

    NASA Astrophysics Data System (ADS)

    Schröder, T.; Grulke, O.; Klinger, T.; Boswell, R. W.; Charles, C.

    2016-01-01

    The plasma parameter dependencies of the dynamics during the expansion of plasma are studied with the use of a versatile particle-in-cell simulation tailored to a plasma expansion experiment [Schröder et al., J. Phys. D: Appl. Phys. 47, 055207 (2014); Schröder et al., Phys. Plasmas 23, 013511 (2016)]. The plasma expansion into a low-density ambient plasma features a propagating ion front that is preceding a density plateau. It has been shown that the front formation is entangled with a wave-breaking mechanism, i.e., an ion collapse [Sack and Schamel, Plasma Phys. Controlled Fusion 27, 717 (1985); Sack and Schamel, Phys. Lett. A 110, 206 (1985)], and the launch of an ion burst [Schröder et al., Phys. Plasmas 23, 013511 (2016)]. The systematic parameter study presented in this paper focuses on the influence on this mechanism its effect on the maximum velocity of the ion front and burst. It is shown that, apart from the well known dependency of the front propagation on the ion sound velocity, it also depends sensitively on the density ratio between main and ambient plasma density. The maximum ion velocity depends further on the initial potential gradient, being mostly influenced by the plasma density ratio in the source and expansion regions. The results of the study are compared with independent numerical studies.

  15. Development, diagnostic and applications of radio-frequency plasma reactor

    NASA Astrophysics Data System (ADS)

    Puac, N.

    2008-07-01

    In many areas of the industry, plasma processing of materials is a vital technology. Nonequilibrium plasmas proved to be able to produce chemically reactive species at a low gas temperature while maintaining highly uniform reaction rates over relatively large areas (Makabe and Petrovic 2006). At the same time nonequilibrium plasmas provide means for good and precise control of the properties of active particles that determine the surface modification. Plasma needle is one of the atmospheric pressure sources that can be used for treatment of the living matter which is highly sensitive when it comes to low pressure or high temperatures (above 40 C). Dependent on plasma conditions, several refined cell responses are induced in mammalian cells (Sladek et al. 2005). It appears that plasma treatment may find many biomedical applications. However, there are few data in the literature about plasma effects on plant cells and tissues. So far, only the effect of low pressure plasmas on seeds was investigated. It was shown that short duration pretreatments by non equilibrium low temperature air plasma were stimulative in light induced germination of Paulownia tomentosa seeds (Puac et al. 2005). As membranes of plants have different properties to those of animals and as they show a wide range of properties we have tried to survey some of the effects of typical plasma which is envisaged to be used in biotechnological applications on plant cells. In this paper we will make a comparison between two configurations of plasma needle that we have used in treatment of biological samples (Puac et al. 2006). Difference between these two configurations is in the additional copper ring that we have placed around glass tube at the tip of the needle. We will show some of the electrical characteristics of the plasma needle (with and without additional copper ring) and, also, plasma emission intensity obtained by using fast ICCD camera.

  16. Endotoxin removal by radio frequency gas plasma (glow discharge)

    NASA Astrophysics Data System (ADS)

    Poon, Angela

    2011-12-01

    Contaminants remaining on implantable medical devices, even following sterilization, include dangerous fever-causing residues of the outer lipopolysaccharide-rich membranes of Gram-negative bacteria such as the common gut microorganism E. coli. The conventional method for endotoxin removal is by Food & Drug Administration (FDA)-recommended dry-heat depyrogenation at 250°C for at least 45 minutes, an excessively time-consuming high-temperature technique not suitable for low-melting or heat-distortable biomaterials. This investigation evaluated the mechanism by which E. coli endotoxin contamination can be eliminated from surfaces during ambient temperature single 3-minute to cumulative 15-minute exposures to radio-frequency glow discharge (RFGD)-generated residual room air plasmas activated at 0.1-0.2 torr in a 35MHz electrodeless chamber. The main analytical technique for retained pyrogenic bio-activity was the Kinetic Chromogenic Limulus Amebocyte Lysate (LAL) Assay, sufficiently sensitive to document compliance with FDA-required Endotoxin Unit (EU) titers less than 20 EU per medical device by optical detection of enzymatic color development corresponding to < 0.5 EU/ml in sterile water extracts of each device. The main analytical technique for identification of chemical compositions, amounts, and changes during sequential reference Endotoxin additions and subsequent RFGD-treatment removals from infrared (IR)-transparent germanium (Ge) prisms was Multiple Attenuated Internal Reflection (MAIR) infrared spectroscopy sensitive to even monolayer amounts of retained bio-contaminant. KimaxRTM 60 mm x 15 mm and 50mm x 15mm laboratory glass dishes and germanium internal reflection prisms were inoculated with E. coli bacterial endotoxin water suspensions at increments of 0.005, 0.05, 0.5, and 5 EU, and characterized by MAIR-IR spectroscopy of the dried residues on the Ge prisms and LAL Assay of sterile water extracts from both glass and Ge specimens. The Ge prism MAIR

  17. Surface Modification of Poly Vinyl Chloride (PVC) Using Low Pressure Argon and Oxygen Plasma

    NASA Astrophysics Data System (ADS)

    Mahmood, Ghoranneviss; Sheila, Shahidi; Jakub, Wiener

    2010-04-01

    In this study, commercial poly vinyl chloride (PVC) films were treated by oxygen and argon plasmas in a cylindrical glass tube which was surrounded by a DC variable magnetic field, with different sample positions in the plasma reactor and also different exposure durations. Effects of the plasma treatment on the hydrophilic properties of the films were studied by measuring the water drop contact angle on the surface of the samples. The surface topography of the untreated and plasma treated films was analyzed and compared by atomic force microscopy (AFM). The optical characteristic changes in treated samples were investigated using reflective spectrophotometry. Also, the chemical changes which appeared on the surface of the samples were investigated using Fourier transform infrared spectroscopy (FTIR). The results show that the plasma treated PVC becomes more hydrophilic with an enhanced wettability. A sharp decrease in the water contact angle may also be a consequence of the surface texturization. The aging effect on wettability of the samples was also investigated. The results show that the effect of oxygen plasma on the surface properties of the samples is more pronounced compared with that of argon plasma.

  18. Effects of oxygen plasma treatment on the surface wettability and dissolution of furosemide compacts.

    PubMed

    Naseem, A; Olliff, C J; Martini, L G; Lloyd, A W

    2003-11-01

    The plasma irradiation of furosemide (frusemide) was investigated as a possible technique for increasing the dissolution rate of this drug. Oxygen plasma was used to generate oxygen-containing functional groups on the surface of the compact to increase the wettability of the surface and the dissolution rate of the drug. Compacts of furosemide (300 mg) were produced using a stainless steel die and punch assembly, which was placed into a KBr press. The time of the plasma treatment was varied to assess the effect if any upon the dissolution rate and the wettability of the drug. Dissolution experiments of the plasma-treated and untreated compacts were carried out using the paddle apparatus method. Dissolution was carried out at 37 degrees C using 1 L of 0.1 M HCl and phosphate buffer (pH 6). The wettability was assessed by contact angle measurements using the sessile drop technique. Untreated and plasma-treated samples were analysed by scanning electron microscopy at x 5000 magnification. Plasma treatment was found to lower the equilibrium contact angle from approximately 50 to 35 degrees but the dissolution rate was not significantly affected. This was attributed to fusion of the surface by the plasma treatment.

  19. Ratio of oxygen to sulfur in the Io plasma torus

    NASA Technical Reports Server (NTRS)

    Shemansky, Donald E.

    1987-01-01

    The relative concentrations of O and S ions in the hot dense region of the Io plasma torus (IPT) are investigated by means of model calculations based on collisional diffusive equilibrium. The spectroscopic constraints and uncertainties encountered in calculating the ion partitioning and the modeling procedures employed are discussed, and the results are presented in tables and graphs and compared with Voyager EUV data and the rocket observations of Skinner and Durrance (1986). It is found that the observed O and S emission from the IPT can be reproduced by models with approximately equal partitioning between O and S species. The assumptions and analyses leading to the conclusion (Moreno et al., 1985) that the IPT is S-dominated (by 3 to 1 or more) are analyzed in detail and rejected.

  20. Sterilization Performance and Material Compatibility of Sterilizer for Dental Instruments using RF Oxygen Plasma

    NASA Astrophysics Data System (ADS)

    Sakai, Yasuhiro; Liu, Zhen; Hayashi, Nobuya; Goto, Masaaki

    2015-09-01

    The sterilization performance and material compatibility of low-pressure RF plasma sterilization method for dental instruments were investigated. RF electrode used in this experiment has been optimized for sterilization of dental instruments. The vial-type biological indicator (BI) simulating tiny space of dental instrument was used for evaluation of the sterilization performance. The pressure in the stainless chamber was fixed at 60 Pa. Sterilization of BI was achieved in shortest time 40 min at 80 W, and the sterilization effect was confirmed using three BIs. Light emission spectra of oxygen plasma indicated that production of atomic oxygen and excited oxygen molecule are maximum at pressure of 20 Pa and 200 Pa, respectively. Sterilization results of BIs indicated that successful rate increases with the oxygen pressure towards 200 Pa. Therefore, the excited oxygen molecule is deduced to be a major factor of the sterilization of BI. Surface morphology of dental instruments such as diamond bar was evaluated using scanning electron microscope (SEM). The deterioration of fine crystals of diamond bar has not observed after the plasma irradiation for 120 min with RF input power was 60W and pressure was 200 Pa.

  1. Ground-Based Tests of Spacecraft Polymeric Materials under OXY-GEN Plasma-Beam

    NASA Astrophysics Data System (ADS)

    Chernik, Vladimir; Novikov, Lev; Gaidar, Anna

    2016-07-01

    Spacecraft LEO mission is accompanied by destruction of polymeric material surface under influence of atomic oxygen flow. Sources of molecular, plasma and ion beams are used for the accelerated ground-based tests of spacecraft materials. In the work application of oxygen plasma accelerator of a duoplasmatron type is described. Plasma particles have been accelerated up to average speed of 13-16 km/s. Influence of such beam on materials leads to more intensive destruction of polymers than in LEO. This fact allows to execute tests in the accelerated time scale by a method of an effective fluence. Special measures were given to decrease a concentration of both gaseous and electrode material impurities in the oxygen beam. In the work the results of simulative tests of spacecraft materials and experiments on LEO are considered. Comparison of plasma beam simulation with LEO data has shown conformity for structures of a number of polymeric materials. The relative erosion yields (normalized with respect to polyimide) of the tested materials are shown practically equal to those in LEO. The obtained results give grounds for using the plasma-generation mode with ion energies of 20-30 eV to accelerated testing of spacecraft materials for long -term LEO missions.

  2. Plasma jet-induced tissue oxygenation: potentialities for new therapeutic strategies

    NASA Astrophysics Data System (ADS)

    Collet, G.; Robert, E.; Lenoir, A.; Vandamme, M.; Darny, T.; Dozias, S.; Kieda, C.; Pouvesle, J. M.

    2014-02-01

    The lack of oxygen is a major reason for the resistance of tumor cells to treatments such as radiotherapies. A large number of recent publications on non-thermal plasma applications in medicine report cell behavior modifications and modulation of soluble factors. This in vivo study tested whether such modifications can lead to vascular changes in response to plasma application. Two in situ optical-based methods were used simultaneously, in real time, to assess the effect of non-thermal plasma on tissue vasculature. Tissue oxygen partial pressure (pO2) was measured using a time-resolved luminescence-based optical probe, and the microvascular erythrocyte flow was determined by laser Doppler flowmetry. When plasma treatment was applied on mouse skin, a rapid pO2 increase (up to 4 times) was subcutaneously measured and correlated with blood flow improvement. Such short duration, i.e. 5 min, plasma-induced effects were shown to be locally restricted to the treated area and lasted over 120 min. Further investigations should elucidate the molecular mechanisms of these processes. However, improvement of oxygenation and perfusion open new opportunities for tumor treatments in combination with radiotherapy, and for tumor blood vessel normalization based strategies.

  3. Oxygen plasma immersion ion implantation treatment to enhance data retention of tungsten nanocrystal nonvolatile memory

    SciTech Connect

    Wang, Jer-Chyi Chang, Wei-Cheng; Lai, Chao-Sung; Chang, Li-Chun; Ai, Chi-Fong; Tsai, Wen-Fa

    2014-03-15

    Data retention characteristics of tungsten nanocrystal (W-NC) memory devices using an oxygen plasma immersion ion implantation (PIII) treatment are investigated. With an increase of oxygen PIII bias voltage and treatment time, the capacitance–voltage hysteresis memory window is increased but the data retention characteristics become degraded. High-resolution transmission electron microscopy images show that this poor data retention is a result of plasma damage on the tunneling oxide layer, which can be prevented by lowering the bias voltage to 7 kV. In addition, by using the elevated temperature retention measurement technique, the effective charge trapping level of the WO{sub 3} film surrounding the W-NCs can be extracted. This measurement reveals that a higher oxygen PIII bias voltage and treatment time induces more shallow traps within the WO{sub 3} film, degrading the retention behavior of the W-NC memory.

  4. A Comparison of Atomic Oxygen Degradation in Low Earth Orbit and in a Plasma Etcher

    NASA Technical Reports Server (NTRS)

    Townsend, Jacqueline A.; Park, Gloria

    1997-01-01

    In low Earth orbit (LEO) significant degradation of certain materials occurs from exposure to atomic oxygen (AO). Orbital opportunities to study this degradation for specific materials are limited and expensive. While plasma etchers are commonly used in ground-based studies because of their low cost and convenience, the environment produced in an etcher chamber differs greatly from the LEO environment. Because of the differences in environment, the validity of using etcher data has remained an open question. In this paper, degradation data for 22 materials from the orbital experiment Evaluation of Oxygen Interaction with Materials (EOIM-3) are compared with data from EOIM-3 control specimens exposed in a typical plasma etcher. This comparison indicates that, when carefully considered, plasma etcher results can produce order-of-magnitude estimates of orbital degradation. This allows the etcher to be used to screen unacceptable materials from further, more expensive tests.

  5. A Fiber Optic Catalytic Sensor for Neutral Atom Measurements in Oxygen Plasma

    PubMed Central

    Zaplotnik, Rok; Vesel, Alenka; Mozetic, Miran

    2012-01-01

    The presented sensor for neutral oxygen atom measurement in oxygen plasma is a catalytic probe which uses fiber optics and infrared detection system to measure the gray body radiation of the catalyst. The density of neutral atoms can be determined from the temperature curve of the probe, because the catalyst is heated predominantly by the dissipation of energy caused by the heterogeneous surface recombination of neutral atoms. The advantages of this sensor are that it is simple, reliable, easy to use, noninvasive, quantitative and can be used in plasma discharge regions. By using different catalyst materials the sensor can also be applied for detection of neutral atoms in other plasmas. Sensor design, operation, example measurements and new measurement procedure for systematic characterization are presented. PMID:22666005

  6. Measurement of plasma wave frequency from absolute stimulated Raman scattering near the quarter-critical surface in a laser plasma

    NASA Astrophysics Data System (ADS)

    Villeneuve, D. M.; Bernard, J. E.; Baldis, H. A.

    1987-12-01

    Thomson scattering techniques were used to measure the frequency of plasma waves near the quarter-critical surface in a well-diagnosed plasma irradiated by a nanosecond CO2 laser with intensity ˜1014 W/cm2. The frequency ωp was shown to be less than ω0/2, in disagreement with the commonly used estimate ωp=ω0/2+ (9)/(8) (ve/c)2ω0. The theory of Afeyan and Williams [Phys. Fluids 28, 3397 (1985)] gives better agreement, and shows that the density scale length is more important than the temperature in determining the frequency shift.

  7. Fine structure in plasma waves and radiation near the plasma frequency in Earth's foreshock

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.

    1994-01-01

    Novel observations are presented of intrunsic fine structure in the frequency spectrum of electomagnetic (EM) radiation and plasma waves near the electron plasma frequency f(sub p) during a period of unusually high interplanetary magnetic field strength. Measured using the wideband receiver on the International Sun-Earth Explorer (ISEE) 1 spacecraft, fine-structured emissions are observed both in the solar wind and the foreshock, The fine structure is shown to correspond to emissions spaced above f(sub p) near half harmonies of the electon cyclotron frequency f(sub ce), i.e., near f(sub p) + nf(sub ce)/2. These appear to be the first space physics observations of emissions spaced by f(sub ce)/2. Indirect but strong arguments are used to discriminate between EM and electrostatic (ES) signals, to identify whether ISEE 1 is in the solar wind or the foreshock, and to determine the relative frequencies of the emissions and the local f(sub p). The data are consistent with generation of the ES and EM emissions in the foreshock, with subsequent propagation of the EM emissions into the solar wind. It remains possible that some emissions currently identified as ES have significant EM character. The ES and EM emisions often merge into one another with minimal changes in frequency, arguing that their source regions and generation mechanisms are related and imposing significant constraints on theories. The f(sub ce)/2 ES and EM fine structures observed may be intrinsic to the emission mechanisms or to superposition of two series of signals with f(sub ce) spacing that differ in starting frequency by f(sub ce)/2. Present theories for nonlinear wave coupling processes, cyclotron maser emission, and other linear instability processes are all unable to explain multiple EM and/or ES components spaced by approximately f(sub ce)/2 above f(sub p) for f(sub p)/f(sub ce) much greater than 1 and typical for shock beams parameters. Suitable avenues for further theoretical research are

  8. Plasma acceleration using a radio frequency self-bias effect

    SciTech Connect

    Rafalskyi, D.; Aanesland, A.

    2015-06-15

    In this work plasma acceleration using a RF self-bias effect is experimentally studied. The experiments are conducted using a novel plasma accelerator system, called Neptune, consisting of an inductively coupled plasma source and a RF-biased set of grids. The plasma accelerator can operate in a steady state mode, producing a plasma flow with separately controlled plasma flux and velocity without any magnetic configuration. The operating pressure at the source output is as low as 0.2 mTorr and can further be decreased. The ion and electron flows are investigated by measuring the ion and electron energy distribution functions both space resolved and with different orientations with respect to the flow direction. It is found that the flow of electrons from the source is highly anisotropic and directed along the ion flow and this global flow of accelerated plasma is well localized in the plasma transport chamber. The maximum flux is about 7.5·10{sup 15} ions s{sup −1} m{sup −2} (at standard conditions) on the axis and decreasing to almost zero at a radial distances of more than 15 cm from the flow axis. Varying the RF acceleration voltage in the range 20–350 V, the plasma flow velocity can be changed between 10 and 35 km/s. The system is prospective for different technology such as space propulsion and surface modification and also interesting for fundamental studies for space-related plasma simulations and investigation of the dynamo effect using accelerated rotating plasmas.

  9. Experimental investigations of the plasma radial uniformity in single and dual frequency capacitively coupled argon discharges

    NASA Astrophysics Data System (ADS)

    Zhao, Kai; Liu, Yong-Xin; Gao, Fei; Liu, Gang-Hu; Han, Dao-Man; Wang, You-Nian

    2016-12-01

    In the current work, the radial plasma density has been measured by utilizing a floating double probe in single and dual frequency capacitively coupled argon discharges operated in a cylindrical reactor, aiming at a better understanding of electromagnetic effects and exploring a method of improving the radial uniformity. The experimental results indicate that for single-frequency plasma sustained at low pressure, the plasma density radial profile exhibits a parabolic distribution at 90 MHz, whereas at 180 MHz, the profile evolves into a bimodal distribution, and both cases indicate poor uniformities. With increasing the pressure, the plasma radial uniformity becomes better for both driving frequency cases. By contrast, when discharges are excited by two frequencies (i.e., 90 + 180 MHz), the plasma radial profile is simultaneously influenced by both sources. It is found that by adjusting the low-frequency to high-frequency voltage amplitude ratio β, the radial profile of plasma density could be controlled and optimized for a wide pressure range. To gain a better plasma uniformity, it is necessary to consider the balance between the standing wave effect, which leads to a maximum plasma density at the reactor center, and the edge field effect, which is responsible for a maximum density near the radial electrode edge. This balance can be controlled either by selecting a proper gas pressure or by adjusting the ratio β.

  10. Oxygen radicals inhibit human plasma acetylhydrolase, the enzyme that catabolizes platelet-activating factor.

    PubMed Central

    Ambrosio, G; Oriente, A; Napoli, C; Palumbo, G; Chiariello, P; Marone, G; Condorelli, M; Chiariello, M; Triggiani, M

    1994-01-01

    Platelet-activating factor (PAF) can exert profound inflammatory effects at very low concentrations. In plasma, PAF is hydrolyzed to lyso-PAF by acetylhydrolase, an enzyme that circulates bound to LDL. Previous studies suggest that oxygen radicals may act synergistically with PAF to potentiate tissue injury. However, mechanisms underlying this interaction have not been elucidated. In this study we investigated whether oxygen radicals may inactivate PAF acetylhydrolase. PAF acetylhydrolase activity was measured in human plasma and purified LDL before and after exposure to radicals (10-20 nmol/min per ml) generated by xanthine/xanthine oxidase. Oxygen radicals induced > 50% loss of PAF acetylhydrolase activity within 60 s and almost complete inactivation by 10 min. This phenomenon was irreversible and independent of oxidative modification of LDL. Inactivation occurred without changes in the affinity constant of the enzyme (Km was 17.9 microM under control conditions and 15.1 microM after exposure to oxygen radicals). Inactivation was prevented by the scavengers superoxide dismutase or dimethylthiourea or by the iron chelator deferoxamine. Thus, superoxide-mediated, iron-catalyzed formation of hydroxyl radicals can rapidly and irreversibly inactivate PAF acetylhydrolase. Since concomitant production of PAF and oxygen radicals can occur in various forms of tissue injury, inactivation of acetylhydrolase might represent one mechanism by which oxygen radicals may potentiate and prolong the proinflammatory effects of PAF. Images PMID:8200975

  11. Degradation of organic fibers in radio frequency plasma

    SciTech Connect

    Finch, J.F.; Poulsen, G.G.; Pitt, W.G. )

    1992-01-01

    Plasma processing can be used to increase adhesion of organic fibers in composite materials, but prolonged exposure can also degrade the fibers, counteracting any adhesive gains. This study investigated the safe upper bounds of plasma processing on four common organic reinforcing fibers: Kevlar 49, Spectra 900, Dacron and Nylon 6. The possible causes of fiber degradation during plasma processing were also examined. Two tests were designed to evaluate fiber tensile strength during and after prolonged exposure to an argon plasma. The first of these tests was a dynamic processing tensile test in which filaments were loaded and exposed to plasma until they failed. The other was a post processing tensile test in which exposed filaments were tensile tested at ambient conditions. These studies determined that all the fibers were adversely affected by the plasma treatment. The degree of degradation was dependent upon the type of fiber, fiber loading, plasma power, and exposure time. The failure of Dacron and Kevlar during plasma processing was dependent upon the applied load. These fibers also showed significant reduction in diameter at failure. In the same type of test the Spectra and Nylon showed no dependency upon load and appeared to fail by melting.

  12. Generation of low-frequency nonlinear currents in plasma by an ultrashort pulse of high-frequency radiation

    SciTech Connect

    Grishkov, V. E.; Uryupin, S. A.

    2015-07-15

    A kinetic theory of low-frequency currents induced in plasma by an ultrashort high-frequency radiation pulse is developed. General expressions for the currents flowing along the propagation direction of the pulse and along the gradient of the field energy density are analyzed both analytically and numerically for pulse durations longer or shorter than or comparable with the electron collision time in plasma. It is demonstrated that the nonlinear current flowing along the gradient of the field energy density can be described correctly only when the modification of the isotropic part of the electron distribution function is taken into account.

  13. The lower subsidiary diffuse plasma resonances and the classification of radio emissions below the plasma frequency

    SciTech Connect

    Osherovich, V.A.; Benson, R.F. )

    1991-11-01

    The diffuse ionospheric resonances D{sub n}, stimulated by topside sounders, have been studied for over 2 decades. These resonances are observed below the plasma frequency f{sub N} between the harmonics of the electron gyrofrequency f{sub H}. The D{sub n} resonances are often accompanied by upper and lower subsidiary branches. The present paper concentrates on the classification of diffuse resonances, one motivation being the possible application to the interpretation of naturally occurring radio emissions in the magnetosphere. Osherovich has shown that the D{sub n} resonances are characterized by a nonequally spaced spectrum of frequencies f{sub D{sub n}} = f{sub Ds}n{sup 1/2} (n = 1, 2, 3, and 4), where f{sub D{sub s}} = 0.95(f{sub N}f{sub H}){sup 1/2}, and that the upper subsidiary resonances D{sub n}{sup +} = (f{sup 2}{sub D{sub n}} + f{sup 2}{sub H}){sup 1/2}. This classification is here extended to include the lower subsidiary resonances D{sub n}{sup minus} (n = 1, 2, 3, and 4), and it is shown that their frequencies are related to f{sub D{sub n}} and f{sub H} by the expression f{sub D{sub n}} = (f{sup 2}{sub D{sub n}} - f{sup 2}{sub H}){sup 1/2}. This result is based on a combination of previously published data and newly scaled ionograms from the Alouette 2 and ISIS 1 topside sounder experiments.

  14. Generation of reactive oxygen and nitrogen species and its effects on DNA damage in lung cancer cells exposed to atmospheric pressure helium/oxygen plasma jets

    NASA Astrophysics Data System (ADS)

    Chung, Tae Hun; Joh, Hea Min; Kim, Sun Ja; Choi, Ji Ye; Kang, Tae-Hong

    2016-09-01

    We investigated the effects of the operating parameters on the generation of reactive oxygen and nitrogen species (RONS) in the gas and liquid phases exposed to atmospheric pressure a pulsed-dc helium plasma jets. The densities of reactive species including OH radicals were obtained at the plasma-liquid surface and inside the plasma-treated liquids using ultraviolet absorption spectroscopy and chemical probe method. And the nitrite concentration was detected by Griess assay. The data are very suggestive that there is a strong correlation among the production of RONS in the plasmas and liquids. Exposure of plasma to cancer cells increases the cellular levels of RONS, which has been linked to apoptosis and the damage of cellular proteins, and may also indirectly cause structural damage to DNA. To identify the correlation between the production of RONS in cells and plasmas, various assay analyses were performed on plasma treated human lung cancer cells (A549) cells. In addition, the effect of additive oxygen gas on the plasma-induced oxidative stress in cancer cells was investigated. It was observed that DNA damage was significantly increased with helium/oxygen plasma compared to with pure helium plasma.

  15. Theory and Observations of High Frequency Alfven Eigenmodes in Low Aspect Ratio Plasma

    SciTech Connect

    N.N. Gorelenkov; E. Fredrickson; E. Belova; C.Z. Cheng; D. Gates; S. Kaye; R. White

    2003-06-27

    New observations of sub-cyclotron frequency instability in low aspect ratio plasma in National Spherical Torus Experiments (NSTX) are reported. The frequencies of observed instabilities correlate with the characteristic Alfven velocity of the plasma. A theory of localized Compressional Alfven Eigenmodes (CAE) and Global shear Alfven Eigenmodes (GAE) in low aspect ratio plasma is presented to explain the observed high frequency instabilities. CAE's/GAE's are driven by the velocity space gradient of energetic super-Alfvenic beam ions via Doppler shifted cyclotron resonances. One of the main damping mechanisms of GAE's, the continuum damping, is treated perturbatively within the framework of ideal MHD. Properties of these cyclotron instabilities ions are presented.

  16. Frequency-dependent quantum capacitance and plasma wave in monolayer transition metal dichalcogenides

    SciTech Connect

    Lam, Kai-Tak; Guo, Jing

    2014-03-10

    Frequency-dependent quantum capacitance C{sub Q} of monolayer transition metal dichalcogenides (TMDs) is computed and compared to that of graphene. It is found that the frequency dependence of C{sub Q} in TMDs differs drastically from that of graphene which has a divergent point. The plasma resonance forms when the quantum capacitance is negative and has the same magnitude as the electrostatic capacitance. The calculation shows that the plasma in TMDs depends on the band-structure-limited velocity, band gap, and doping density, which can be controlled via gate biases. The plasma frequencies of TMDs are in the rage of terahertz useful for various applications.

  17. Propagation of terahertz electromagnetic wave in plasma with inhomogeneous collision frequency

    SciTech Connect

    Tian, Yuan; Han, YiPing; Ling, YingJie; Ai, Xia

    2014-02-15

    In this paper, we investigate the absorption spectra of terahertz electromagnetic wave in plasma with inhomogeneous collision frequency. Profiles are introduced to describe the non-uniformity of collision frequency. It is interesting to find that when the plasma is collision frequency inhomogeneous, the absorption spectrum would decreases faster than that in uniform plasma. And the rate of decreasing would be different when the profile changes. Two parameters are set up to predict how the profiles affect the absorption spectra. Furthermore, the effects of electron density are also considered.

  18. Surface activation of cyclo olefin polymer by oxygen plasma discharge: a molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Soberon, Felipe

    2014-07-01

    Thermoplastic substrates made of cyclo olefin polymer (COP) are treated with oxygen plasma discharges to introduce polar groups at the surface. This is the first step in the process of surface functionalization of COP substrates used in biosensor devices. A molecular dynamics model of basic COP structure is implemented using the second-generation reactive empirical bond order (REBO) potentials for hydrocarbon-oxygen interactions. The model includes covalent bond and Van der Waals interactions. The bombardment of a COP surface with mono-energetic atomic oxygen ions, energy in the range 1-35 eV, is simulated and reported here. The dynamics of the substrate modification reveals that the substrate top layer is de-hydrogenated and subsequently builds up an oxygen-carbon matrix layer, ˜10 Å thick. Analysis of the modified substrates indicates that surface yield is predominantly peroxide groups.

  19. Surface Plasma Arc by Radio-Frequency Control Study (SPARCS)

    SciTech Connect

    Ruzic, David N.

    2013-04-29

    This paper is to summarize the work carried out between April 2012 and April 2013 for development of an experimental device to simulate interactions of o -normal detrimental events in a tokamak and ICRF antenna. The work was mainly focused on development of a pulsed plasma source using theta pinch and coaxial plasma gun. This device, once completed, will have a possible application as a test stand for high voltage breakdown of an ICRF antenna in extreme events in a tokamak such as edge-localized modes or disruption. Currently, DEVeX does not produce plasma with high temperature enough to requirement for an ELM simulator. However, theta pinch is a good way to produce high temperature ions. The unique characteristic of plasma heating by a theta pinch is advantageous for an ELM simulator due to its effective ion heating. The objective of the proposed work, therefore, is to build a test facility using the existing theta pinch facility in addition to a coaxial plasma gun. It is expected to produce a similar pulsed-plasma heat load to the extreme events in tokamaks and to be applied for studying interactions of hot plasma and ICRF antennas.

  20. Targeting cancer cells with reactive oxygen and nitrogen species generated by atmospheric-pressure air plasma.

    PubMed

    Ahn, Hak Jun; Kim, Kang Il; Hoan, Nguyen Ngoc; Kim, Churl Ho; Moon, Eunpyo; Choi, Kyeong Sook; Yang, Sang Sik; Lee, Jong-Soo

    2014-01-01

    The plasma jet has been proposed as a novel therapeutic method for cancer. Anticancer activity of plasma has been reported to involve mitochondrial dysfunction. However, what constituents generated by plasma is linked to this anticancer process and its mechanism of action remain unclear. Here, we report that the therapeutic effects of air plasma result from generation of reactive oxygen/nitrogen species (ROS/RNS) including H2O2, Ox, OH-, •O2, NOx, leading to depolarization of mitochondrial membrane potential and mitochondrial ROS accumulation. Simultaneously, ROS/RNS activate c-Jun NH2-terminal kinase (JNK) and p38 kinase. As a consequence, treatment with air plasma jets induces apoptotic death in human cervical cancer HeLa cells. Pretreatment of the cells with antioxidants, JNK and p38 inhibitors, or JNK and p38 siRNA abrogates the depolarization of mitochondrial membrane potential and impairs the air plasma-induced apoptotic cell death, suggesting that the ROS/RNS generated by plasma trigger signaling pathways involving JNK and p38 and promote mitochondrial perturbation, leading to apoptosis. Therefore, administration of air plasma may be a feasible strategy to eliminate cancer cells.

  1. Atomic oxygen behavior at downstream of AC excited atmospheric pressure He plasma jet

    NASA Astrophysics Data System (ADS)

    Takeda, Keigo; Ishikawa, Kenji; Tanaka, Hiromasa; Sekine, Makoto; Hori, Masaru

    2016-09-01

    Applications of atmospheric pressure plasma jets (APPJ) have been investigated in the plasma medical fields such as cancer therapy, blood coagulation, etc. Reactive species generated by the plasma jet interacts with the biological surface. Therefore, the issue attracts much attentions to investigate the plasma effects on targets. In our group, a spot-size AC excited He APPJ have been used for the plasma medicine. From diagnostics of the APPJ using optical emission spectroscopy, the gas temperature and the electron density was estimated to be 299 K and 3.4 ×1015 cm-3. The AC excited He APPJ which affords high density plasma at room temperature is considered to be a powerful tool for the medical applications. In this study, by using vacuum ultraviolet absorption spectroscopy, the density of atomic oxygen on a floating copper as a target irradiated by the He APPJ was measured as a function of the distance between the plasma source and the copper wire. The measured density became a maximum value around 8 ×1013 cm-3 at 12 mm distance, and then decreased over the distance. It is considered that the behavior was due to the changes in the plasma density on the copper wire and influence of ambient air.

  2. Properties of radio-frequency heated argon confined uranium plasmas

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Pure uranium hexafluoride (UF6) was injected into an argon confined, steady state, rf-heated plasma within a fused silica peripheral wall test chamber. Exploratory tests conducted using an 80 kW rf facility and different test chamber flow configurations permitted selection of the configuration demonstrating the best confinement characteristics and minimum uranium compound wall coating. The overall test results demonstrated applicable flow schemes and associated diagnostic techniques were developed for the fluid mechanical confinement and characterization of uranium within an rf plasma discharge when pure UF6 is injected for long test times into an argon-confined, high-temperature, high-pressure, rf-heated plasma.

  3. Non-thermal dielectric barrier discharge plasma induces angiogenesis through reactive oxygen species

    PubMed Central

    Arjunan, Krishna Priya; Friedman, Gary; Fridman, Alexander; Clyne, Alisa Morss

    2012-01-01

    Vascularization plays a key role in processes such as wound healing and tissue engineering. Non-thermal plasma, which primarily produces reactive oxygen species (ROS), has recently emerged as an efficient tool in medical applications including blood coagulation, sterilization and malignant cell apoptosis. Liquids and porcine aortic endothelial cells were treated with a non-thermal dielectric barrier discharge plasma in vitro. Plasma treatment of phosphate-buffered saline (PBS) and serum-free medium increased ROS concentration in a dose-dependent manner, with a higher concentration observed in serum-free medium compared with PBS. Species concentration inside cells peaked 1 h after treatment, followed by a decrease 3 h post treatment. Endothelial cells treated with a plasma dose of 4.2 J cm–2 had 1.7 times more cells than untreated samples 5 days after plasma treatment. The 4.2 J cm–2 plasma dose increased two-dimensional migration distance by 40 per cent compared with untreated control, while the number of cells that migrated through a three-dimensional collagen gel increased by 15 per cent. Tube formation was also enhanced by plasma treatment, with tube lengths in plasma-treated samples measuring 2.6 times longer than control samples. A fibroblast growth factor-2 (FGF-2) neutralizing antibody and ROS scavengers abrogated these angiogenic effects. These data indicate that plasma enhanced proliferation, migration and tube formation is due to FGF-2 release induced by plasma-produced ROS. Non-thermal plasma may be used as a potential tool for applying ROS in precise doses to enhance vascularization. PMID:21653568

  4. Wakefield evolution and electron acceleration in interaction of frequency-chirped laser pulse with inhomogeneous plasma

    NASA Astrophysics Data System (ADS)

    Rezaei-Pandari, M.; Niknam, A. R.; Massudi, R.; Jahangiri, F.; Hassaninejad, H.; Khorashadizadeh, S. M.

    2017-02-01

    The nonlinear interaction of an ultra-short intense frequency-chirped laser pulse with an underdense plasma is studied. The effects of plasma inhomogeneity and laser parameters such as chirp, pulse duration, and intensity on plasma density and wakefield evolutions, and electron acceleration are examined. It is found that a properly chirped laser pulse could induce a stronger laser wakefield in an inhomogeneous plasma and result in higher electron acceleration energy. It is also shown that the wakefield amplitude is enhanced by increasing the slope of density in the inhomogeneous plasma.

  5. Characterization of low-pressure microwave and radio frequency discharges in oxygen applying optical emission spectroscopy and multipole resonance probe

    NASA Astrophysics Data System (ADS)

    Steves, Simon; Styrnoll, Tim; Mitschker, Felix; Bienholz, Stefan; Nikita, Bibinov; Awakowicz, Peter

    2013-11-01

    Optical emission spectroscopy (OES) and multipole resonance probe (MRP) are adopted to characterize low-pressure microwave (MW) and radio frequency (RF) discharges in oxygen. In this context, both discharges are usually applied for the deposition of permeation barrier SiOx films on plastic foils or the inner surface of plastic bottles. For technological reasons the MW excitation is modulated and a continuous wave (cw) RF bias is used. The RF voltage produces a stationary low-density plasma, whereas the high-density MW discharge is pulsed. For the optimization of deposition process and the quality of the deposited barrier films, plasma conditions are characterized using OES and MRP. To simplify the comparison of applied diagnostics, both MW and RF discharges are studied separately in cw mode. The OES and MRP diagnostic methods complement each other and provide reliable information about electron density and electron temperature. In the MW case, electron density amounts to ne = (1.25 ± 0.26) × 1017 m-3, and kTe to 1.93 ± 0.20 eV, in the RF case ne = (6.8 ± 1.8)×1015 m-3 and kTe = 2.6 ± 0.35 eV. The corresponding gas temperatures are 760±40 K and 440±20 K.

  6. In situ oxygen plasma cleaning of a PECVD source for hard disk overcoats

    NASA Astrophysics Data System (ADS)

    Ochs, D.; Cord, B.

    Reducing the thickness of the diamond-like carbon protective overcoat to a thickness of about 2-3 nm is one major key to increase the recording density of magnetic disk drives. Plasma-enhanced chemical vapor deposition (PECVD) deposited carbon layers have been shown to be denser and harder than those produced by conventional sputter deposition. One key problem of PECVD deposited carbon is the contamination of the carbon film by particles produced inside the carbon source after long-time operation. This particle production limits the runtime of the source drastically. To avoid this particle generation the source was cleaned by an intermittent in situ oxygen plasma process. The cleaning efficiency was investigated by recording the pressure change inside the source during the cleaning process caused by the CO production. The ratio of the cleaning time and the deposition time shows no significant dependence on the deposition time. An almost linear increase of the ratio with the acetylene flow was observed. This results from a higher deposition rate at higher acetylene flow, leading to a higher contamination inside the source. A strong dependence of the cleaning rate on the oxygen flow in the cleaning process was measured. More oxygen leads to a strong decrease of the needed cleaning time. Adding Ar gas to the oxygen discharge shows no improvement of the needed cleaning time. The cleaning process seems to be dependent only on the amount of reactive oxygen species in the discharge .

  7. Plasma reactivity in high-power impulse magnetron sputtering through oxygen kinetics

    SciTech Connect

    Vitelaru, Catalin; Lundin, Daniel; Brenning, Nils; Minea, Tiberiu

    2013-09-02

    The atomic oxygen metastable dynamics in a Reactive High-Power Impulse Magnetron Sputtering (R-HiPIMS) discharge has been characterized using time-resolved diode laser absorption in an Ar/O{sub 2} gas mixture with a Ti target. Two plasma regions are identified: the ionization region (IR) close to the target and further out the diffusion region (DR), separated by a transition region. The μs temporal resolution allows identifying the main atomic oxygen production and destruction routes, which are found to be very different during the pulse as compared to the afterglow as deduced from their evolution in space and time.

  8. Numerical Experiments on Oxygen Plasma Focus: Scaling Laws of Soft X-Ray Yields

    NASA Astrophysics Data System (ADS)

    Akel, M.

    2013-08-01

    Numerical experiments have been investigated on UNU/ICTP PFF low energy plasma focus device with oxygen filling gas. In these numerical experiments, the temperature window of 119-260 eV has been used as a suitable temperature range for generating oxygen soft X-rays. The Lee model was applied to characterize the UNU/ICTP PFF plasma focus. The optimum soft X-ray yield (Ysxr) was found to be 0.75 J, with the corresponding efficiency of about 0.03 % at pressure of 2.36 Torr and the end axial speed was va = 5 cm/μs. The practical optimum combination of p0, z0 and `a' for oxygen Ysxr was found to be 0.69 Torr, 4.8 cm and 2.366 cm respectively, with the outer radius b = 3.2 cm. This combination gives Ysxr ~ 5 J, with the corresponding efficiency of about 0.16 %. Thus we expect to increase the oxygen Ysxr of UNU/ICTP PFF, without changing the capacitor bank, merely by changing the electrode configuration and operating pressure. Scaling laws on oxygen soft X-ray yield, in terms of storage energies E0, peak discharge current Ipeak and focus pinch current Ipinch were found over the range from 1 kJ to 1 MJ. It was found that the oxygen soft X-ray yields scale well with and for the low inductance (L0 = 30 nH) (where yields are in J and currents in kA). While the soft X-ray yield scaling laws in terms of storage energies were found to be as (E0 in kJ and Ysxr in J) with the scaling showing gradual deterioration as E0 rises over the range. The oxygen soft X-ray yield emitted from plasma focus is found to be about 8.7 kJ for storage energy of 1 MJ. The optimum efficiency for soft X-ray yield (1.1 %) is with capacitor bank energy of 120 kJ. This indicates that oxygen plasma focus is a good soft X-ray source when properly designed.

  9. Oxygen Gas Barrier Properties of Hydrogenated Amorphous Carbon Thin Films Deposited with a Pulse-Biased Inductively Coupled Plasma Chemical Vapor Deposition Method

    NASA Astrophysics Data System (ADS)

    Baek, Sang-min; Shirafuji, Tatsuru; Cho, Sung-pyo; Saito, Nagahiro; Takai, Osamu

    2010-08-01

    Hydrogenated amorphous carbon (a-C:H) films have been deposited on poly(ethylene terephthalate) (PET) films with an pulse-biased inductively coupled plasma chemical vapor deposition method using CH4 and C2H2 gases. We have investigated the effects of the pulse-bias frequency on the oxygen transmission rate (OTR) of the a-C:H-coated PET sample, and discussed relationship between the OTR characteristics and the structure of the films based on the results of Raman and infrared absorption spectroscopy. In case of CH4 plasmas, the OTR of the sample has been reduced down to 1.12 cm3/(m2·day·atm) by increasing the bias-frequency to 2 kHz, and the structure of the a-C:H films has been modified from polymer-like to tetrahedral one. In case of C2H2 plasmas, the OTR of the samples has been 1.18 cm3/(m2·day·atm) with the lower bias frequency of 0.5 kHz, and has not shown strong dependence on the pulse-bias frequency. This has been explained by the fact that the films prepared with C2H2 plasma can be modified to tetrahedral structures by applying the bias with the lower frequency.

  10. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Collision frequency shift of a short electromagnetic pulse

    NASA Astrophysics Data System (ADS)

    Chegotov, M. V.

    2004-03-01

    The frequency shift of a short electromagnetic pulse interaction with a plasma-like medium is discovered and studied. The shift is caused by elastic collisions of free electrons with ions or neutral particles.

  11. Investigation of the effects of electron plasma frequency on the operation of a helix TWT

    NASA Astrophysics Data System (ADS)

    Oksuz, Lutfi; Haytural, Necati; Uygun, Emre; Bozduman, Ferhat; Yesiltepe, Hakan; Gulec, Ali

    2016-10-01

    The oscillations of electrons are an important subject for the design procedure of linear beam tubes such as klystrons and TWTs. These oscillation frequencies may be affected by the finite region of the tube if the plasma wavelength of the electrons are larger than the bounding region of the device, leading to a reduced plasma frequency which further leads to an increase in wavelength. Following the Pierce's theory on traveling wave tubes, it is seen that the reduced plasma frequency takes place in space charge terms which also include the Pierce's gain parameter C. In this study the effects of plasma frequency on the operation of a helix TWT are investigated using CST Particle Studio. This project is supported by TUBITAK with project number: 1140075.

  12. Spectroscopic measurement of high-frequency electric fields in the interaction of explosive debris plasma with magnetized background plasma

    SciTech Connect

    Bondarenko, A. S. Schaeffer, D. B.; Everson, E. T.; Clark, S. E.; Constantin, C. G.; Niemann, C.

    2014-12-15

    The collision-less transfer of momentum and energy from explosive debris plasma to magnetized background plasma is a salient feature of various astrophysical and space environments. While much theoretical and computational work has investigated collision-less coupling mechanisms and relevant parameters, an experimental validation of the results demands the measurement of the complex, collective electric fields associated with debris-background plasma interaction. Emission spectroscopy offers a non-interfering diagnostic of electric fields via the Stark effect. A unique experiment at the University of California, Los Angeles, that combines the Large Plasma Device (LAPD) and the Phoenix laser facility has investigated the marginally super-Alfvénic, quasi-perpendicular expansion of a laser-produced carbon (C) debris plasma through a preformed, magnetized helium (He) background plasma via emission spectroscopy. Spectral profiles of the He II 468.6 nm line measured at the maximum extent of the diamagnetic cavity are observed to intensify, broaden, and develop equally spaced modulations in response to the explosive C debris, indicative of an energetic electron population and strong oscillatory electric fields. The profiles are analyzed via time-dependent Stark effect models corresponding to single-mode and multi-mode monochromatic (single frequency) electric fields, yielding temporally resolved magnitudes and frequencies. The proximity of the measured frequencies to the expected electron plasma frequency suggests the development of the electron beam-plasma instability, and a simple saturation model demonstrates that the measured magnitudes are feasible provided that a sufficiently fast electron population is generated during C debris–He background interaction. Potential sources of the fast electrons, which likely correspond to collision-less coupling mechanisms, are briefly considered.

  13. Temperature of hydrogen radio frequency plasma under dechlorination process of polychlorinated biphenyls

    NASA Astrophysics Data System (ADS)

    Inada, Y.; Abe, K.; Kumada, A.; Hidaka, K.; Amano, K.; Itoh, K.; Oono, T.

    2014-10-01

    It has been reported that RF (radio frequency) hydrogen plasmas promote the dechlorination process of PCBs (polychlorinated biphenyls) under irradiation of MW (microwave). A relative emission intensity spectroscope system was used for single-shot imaging of two-dimensional temperature distributions of RF hydrogen plasmas generated in chemical solutions with several mixing ratios of isopropyl alcohol (IPA) and insulation oil under MW irradiation. Our experimental results showed that the plasma generation frequencies for the oil-contaminating solutions were higher than that for the pure IPA solution. In addition, the plasma temperature in the compound liquids including both oil and IPA was higher than that in the pure IPA and oil solutions. A combination of the plasma temperature measurements and plasma composition analysis indicated that the hydrogen radicals generated in a chemical solution containing the equal volumes of IPA and oil were almost the same amounts of H and H+, while those produced in the other solutions were mainly H.

  14. Temperature of hydrogen radio frequency plasma under dechlorination process of polychlorinated biphenyls

    SciTech Connect

    Inada, Y. Abe, K.; Kumada, A.; Hidaka, K.; Amano, K.; Itoh, K.; Oono, T.

    2014-10-27

    It has been reported that RF (radio frequency) hydrogen plasmas promote the dechlorination process of PCBs (polychlorinated biphenyls) under irradiation of MW (microwave). A relative emission intensity spectroscope system was used for single-shot imaging of two-dimensional temperature distributions of RF hydrogen plasmas generated in chemical solutions with several mixing ratios of isopropyl alcohol (IPA) and insulation oil under MW irradiation. Our experimental results showed that the plasma generation frequencies for the oil-contaminating solutions were higher than that for the pure IPA solution. In addition, the plasma temperature in the compound liquids including both oil and IPA was higher than that in the pure IPA and oil solutions. A combination of the plasma temperature measurements and plasma composition analysis indicated that the hydrogen radicals generated in a chemical solution containing the equal volumes of IPA and oil were almost the same amounts of H and H{sup +}, while those produced in the other solutions were mainly H.

  15. Oxygen transport through polyethylene terephthalate (PET) coated with plasma-polymerized acetylene at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Wemlinger, Erik; Pedrow, Patrick; Garcia-Pérez, Manuel; Sablani, Shyam

    2011-10-01

    Moser et al. have shown that oxygen transport through polyethyleneterephthalate (PET) is reduced by a factor of up to 120 when, at reduced pressure, hydrogenated amorphous carbon film with thickness less than 100 nm is applied to the PET substrate. Our work includes using atmospheric pressure cold plasma to grow a plasma-polymerized acetylene film on PET substrate and measuring reductions in oxygen transport. The reactor utilizes corona discharges and is operated at 60 Hz with a maximum voltage of 10 kV RMS. Corona streamers emanate from an array of needles with an average radius of curvature of 50 μm. The reactor utilizes a cylindrical reaction chamber with a vertical orientation such that argon carrier gas and acetylene precursor gas are introduced at the top then pass through the cold plasma activation zone and then through a grounded stainless steel mesh. Acetylene radicals are incident on the PET substrate and form plasma-polymerized acetylene film. Moser et al. have shown that oxygen transport through polyethyleneterephthalate (PET) is reduced by a factor of up to 120 when, at reduced pressure, hydrogenated amorphous carbon film with thickness less than 100 nm is applied to the PET substrate. Our work includes using atmospheric pressure cold plasma to grow a plasma-polymerized acetylene film on PET substrate and measuring reductions in oxygen transport. The reactor utilizes corona discharges and is operated at 60 Hz with a maximum voltage of 10 kV RMS. Corona streamers emanate from an array of needles with an average radius of curvature of 50 μm. The reactor utilizes a cylindrical reaction chamber with a vertical orientation such that argon carrier gas and acetylene precursor gas are introduced at the top then pass through the cold plasma activation zone and then through a grounded stainless steel mesh. Acetylene radicals are incident on the PET substrate and form plasma-polymerized acetylene film. E.M. Moser, R. Urech, E. Hack, H. Künzli, E. Müller, Thin

  16. Cleaning of diamond nanoindentation probes with oxygen plasma and carbon dioxide snow

    SciTech Connect

    Morris, Dylan J.

    2009-12-15

    Diamond nanoindentation probes may perform thousands of indentations over years of service life. There is a broad agreement that the probes need frequent cleaning, but techniques for doing so are mostly anecdotes shared between experimentalists. In preparation for the measurement of the shape of a nanoindentation probe by a scanning probe microscope, cleaning by carbon dioxide snow jets and oxygen plasma was investigated. Repeated indentation on a thumbprint-contaminated surface formed a compound that was very resistant to removal by solvents, CO{sub 2} snow, and plasma. CO{sub 2} snow cleaning is found to be a generally effective cleaning procedure.

  17. Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet

    NASA Astrophysics Data System (ADS)

    Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Chung, T. H.; Kang, Tae-Hong

    2014-10-01

    The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment.

  18. Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet.

    PubMed

    Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Chung, T H; Kang, Tae-Hong

    2014-10-16

    The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment.

  19. Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet

    PubMed Central

    Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Chung, T. H.; Kang, Tae-Hong

    2014-01-01

    The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment. PMID:25319447

  20. Observation of inactivation of Bacillus sbtilis spores under exposures of oxygen added argon atmospheric pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Shen, Jie; Cheng, Cheng; Zhao, Ying; Xiao, Dezhi; Lan, Yan; Xie, Hongbing; Cheng, Junli; Meng, Yuedong; Li, Jiangang; Chu, Paul K.

    2014-11-01

    The inactivation of Bacillus subtilis spores by an Ar plasma jet mixed with different amounts of oxygen is reported. 5.8 × 106 B. subtilis spores are sterilized by an Ar/O2 (8.7%) plasma jet after exposure for 2 min. The densities of ozone and oxygen radicals in the Ar/O2 plasma jet increase with oxygen concentration and are estimated by optical spectroscopy diagnostic. The malondialdehyde (MDA) test shows that oxygen radicals participate in bacterial inactivation. Scanning electron microscopy (SEM) reveals the deformation of the spore shape due to etching by oxygen radicals and the dependence of the degree of deformation on the density of oxygen radicals.

  1. Plasma Electron Number Density and Electron-Neutral Collision Frequency from Complex Impedance Measurements.

    DTIC Science & Technology

    1982-12-01

    observed effects is Shown in Figure 22. This model is equivalent to the model tested over a limited frequency range ( Hayt , W.H., 1962:458). Also, the...Plasma Physics. Cambridge, Mass.: The M.I.T. Press, 1967. 3. Chen, F. F. Introduction to Plasma Physics. New York: Plenum Press, 1977: 4. Hayt , W. H

  2. Characteristics of dual-frequency capacitively coupled SF6/O2 plasma and plasma texturing of multi-crystalline silicon

    NASA Astrophysics Data System (ADS)

    Xu, Dong-Sheng; Zou, Shuai; Xin, Yu; Su, Xiao-Dong; Wang, Xu-Sheng

    2014-06-01

    Due to it being environmentally friendly, much attention has been paid to the dry plasma texturing technique serving as an alternative candidate for multicrystalline silicon (mc-Si) surface texturing. In this paper, capacitively coupled plasma (CCP) driven by a dual frequency (DF) of 40.68 MHz and 13.56 MHz is first used for plasma texturing of mc-Si with SF6/O2 gas mixture. Using a hairpin resonant probe and optical emission techniques, DF-CCP characteristics and their influence on mc-silicon surface plasma texturing are investigated at different flow rate ratios, pressures, and radio-frequency (RF) input powers. Experimental results show that suitable plasma texturing of mc-silicon occurs only in a narrow range of plasma parameters, where electron density ne must be larger than 6.3 × 109 cm-3 and the spectral intensity ratio of the F atom to that of the O atom ([F]/[O]) in the plasma must be between 0.8 and 0.3. Out of this range, no cone-like structure is formed on the mc-silicon surface. In our experiments, the lowest reflectance of about 7.3% for mc-silicon surface texturing is obtained at an [F]/[O] of 0.5 and ne of 6.9 × 109 cm-3.

  3. Effects of gas pressure on 60/13.56 MHz dual-frequency capacitively coupled plasmas

    SciTech Connect

    Yuan, Q. H.; Yin, G. Q.; Xin, Y.; Ning, Z. Y.

    2011-05-15

    The electron energy probability functions (EEPFs) were measured with increasing gas pressure in 60/13.56 MHz dual-frequency capacitively coupled plasma (DF-CCP) using compensated Langmiur electrostatic probe. The transition pressure of heating mode from collisionless to collisional heating in 60/13.56 MHz DF-CCP is found to be significantly lower than that in 13.56 MHz single-frequency CCP. As the pressure increases, the EEPFs change from bi-Maxwellian to Druyvesteyn type which is similar with that in 60 MHz single-frequency CCP. The pressure dependence of electron densities, effective electron temperatures, floating potentials, and plasma potentials in 60/13.56 MHz DF-CCP were measured and were compared with that in 60 MHz single-frequency CCP. The pressure dependence of these plasma parameters in 60/13.56 MHz DF-CCP is similar with that in 60 MHz single-frequency CCP.

  4. Nonequilibrium atmospheric pressure plasma jet using a combination of 50 kHz/2 MHz dual-frequency power sources

    SciTech Connect

    Zhou, Yong-Jie; Yuan, Qiang-Hua; Li, Fei; Wang, Xiao-Min; Yin, Gui-Qin; Dong, Chen-Zhong

    2013-11-15

    An atmospheric pressure plasma jet is generated by dual sinusoidal wave (50 kHz and 2 MHz). The dual-frequency plasma jet exhibits the advantages of both low frequency and radio frequency plasmas, namely, the long plasma plume and the high electron density. The radio frequency ignition voltage can be reduced significantly by using dual-frequency excitation compared to the conventional radio frequency without the aid of the low frequency excitation source. A larger operating range of α mode discharge can be obtained using dual-frequency excitation which is important to obtain homogeneous and low-temperature plasma. A larger controllable range of the gas temperature of atmospheric pressure plasma could also be obtained using dual-frequency excitation.

  5. Photooxidation of plasma polymerized polydimethylsiloxane film by 172 nm vacuum ultraviolet light irradiation in dilute oxygen

    SciTech Connect

    Ichikawa, S.

    2006-08-01

    Plasma polymerized polydimethylsiloxane films irradiated under different partial pressures of oxygen with a 172 nm vacuum ultraviolet light were investigated in order to clarify the roles of molecular oxygen and photons in photooxidation. The thickness, densities, surface roughness, elemental compositions, and molecular structures of the irradiated and unirradiated films were examined by using glazing incidence x-ray reflectivity, Rutherford backscattering, infrared, and x-ray absorption (XAS) spectroscopies. Photooxidation is hardly promoted by irradiation in a high vacuum of 1x10{sup -4} Pa, though photodesorption of the methyl group and formation of Si-H bonds were observed. Silica films thicker than 140 nm were formed at room temperature by irradiating them in low pressure oxygen gases. The degree of oxidation was smaller for the oxygen pressure of 10 kPa than for 83 Pa. Si K-edge XAS was performed to clarify the change of coordination environment of silicon by photooxidation in dilute oxygen flow containing less than 5 ppm of molecular oxygen.

  6. Modulations of the plasma uniformity by low frequency sources in a large-area dual frequency inductively coupled plasma based on fluid simulations

    SciTech Connect

    Sun, Xiao-Yan; Zhang, Yu-Ru; Li, Xue-Chun; Wang, You-Nian

    2015-05-15

    As the wafer size increases, dual frequency (DF) inductively coupled plasma (ICP) sources have been proposed as an effective method to achieve large-area uniform plasma processing. A two-dimensional (2D) self-consistent fluid model, combined with an electromagnetic module, has been employed to investigate the influence of the low frequency (LF) source on the plasma radial uniformity in an argon DF discharge. When the DF antenna current is fixed at 10 A, the bulk plasma density decreases significantly with the LF due to the less efficient heating, and the best radial uniformity is obtained at 3.39 MHz. As the LF decreases to 2.26 MHz, the plasma density is characterized by an edge-high profile, and meanwhile the maximum of the electron temperature appears below the outer two-turn coil. Moreover, the axial ion flux at 3.39 MHz is rather uniform in the center region except at the radial edge of the substrate, where a higher ion flux is observed. When the inner five-turn coil frequency is fixed at 2.26 MHz, the plasma density profiles shift from edge-high over uniform to center-high as the LF coil current increases from 6 A to 18 A, and the best plasma uniformity is obtained at 14 A. In addition, the maximum of the electron temperature becomes lower with a second peak appears at the radial position of r = 9 cm at 18 A.

  7. Distinctive plume formation in atmospheric Ar and He plasmas in microwave frequency band and suitability for biomedical applications

    SciTech Connect

    Lee, H. Wk.; Kang, S. K.; Won, I. H.; Kim, H. Y.; Kwon, H. C.; Sim, J. Y.; Lee, J. K.

    2013-12-15

    Distinctive discharge formation in atmospheric Ar and He plasmas was observed in the microwave frequency band using coaxial transmission line resonators. Ar plasmas formed a plasma plume whereas He formed only confined plasmas. As the frequency increased from 0.9 GHz to 2.45 GHz, the Ar plasma exhibited contraction and filamentation, and the He plasmas were constricted. Various powers and gas flow rates were applied to identify the effect of the electric field and gas flow rate on plasma plume formation. The He plasmas were more strongly affected by the electric field than the Ar plasmas. The breakdown and sustain powers yielded opposite results from those for low-frequency plasmas (∼kHz). The phenomena could be explained by a change in the dominant ionization process with increasing frequency. Penning ionization and the contribution of secondary electrons in sheath region reduced as the frequency increased, leading to less efficient ionization of He because its ionization and excitation energies are higher than those of Ar. The emission spectra showed an increase in the NO and N{sub 2} second positive band in both the Ar and He plasmas with increasing frequency whereas the hydroxyl radical and atomic O peaks did not increase with increasing frequency but were highest at particular frequencies. Further, the frequency effect of properties such as the plasma impedance, electron density, and device efficiency were presented. The study is expected to be helpful for determining the optimal conditions of plasma systems for biomedical applications.

  8. Surface monofunctionalized polymethyl pentene hollow fiber membranes by plasma treatment and hemocompatibility modification for membrane oxygenators

    NASA Astrophysics Data System (ADS)

    Huang, Xin; Wang, Weiping; Zheng, Zhi; Fan, Wenling; Mao, Chun; Shi, Jialiang; Li, Lei

    2016-01-01

    The hemocompatibility of polymethyl pentene (PMP) hollow fiber membranes (HFMs) was improved through surface modification for membrane oxygenator applications. The modification was performed stepwise with the following: (1) oxygen plasma treatment, (2) functionalization of monosort hydroxyl groups through NaBH4 reduction, and (3) grafting 2-methacryloyloxyethyl phosphorylcholine (MPC) or heparin. SEM, ATR-FTIR, and XPS analyses were conducted to confirm successful grafting during the modification. The hemocompatibility of PMP HFMs was analyzed and compared through protein adsorption, platelet adhesion, and coagulation tests. Pure CO2 and O2 permeation rates, as well as in vitro gas exchange rates, were determined to evaluate the mass transfer properties of PMP HFMs. SEM results showed that different nanofibril topographies were introduced on the HFM surface. ATR-FTIR and XPS spectra indicated the presence of functionalization of monosort hydroxyl group and the grafting of MPC and heparin. Hemocompatibility evaluation results showed that the modified PMP HFMs presented optimal hemocompatibility compared with pristine HFMs. Gas permeation results revealed that gas permeation flux increased in the modified HFMs because of dense surface etching during the plasma treatment. The results of in vitro gas exchange rates showed that all modified PMP HFMs presented decreased gas exchange rates because of potential surface fluid wetting. The proposed strategy exhibits a potential for fabricating membrane oxygenators for biomedical applications to prevent coagulation formation and alter plasma-induced surface topology and composition.

  9. Argon–oxygen dc magnetron discharge plasma probed with ion acoustic waves

    SciTech Connect

    Saikia, Partha Saikia, Bipul Kumar; Goswami, Kalyan Sindhu; Phukan, Arindam

    2014-05-15

    The precise determination of the relative concentration of negative ions is very important for the optimization of magnetron sputtering processes, especially for those undertaken in a multicomponent background produced by adding electronegative gases, such as oxygen, to the discharge. The temporal behavior of an ion acoustic wave excited from a stainless steel grid inside the plasma chamber is used to determine the relative negative ion concentration in the magnetron discharge plasma. The phase velocity of the ion acoustic wave in the presence of negative ions is found to be faster than in a pure argon plasma, and the phase velocity increases with the oxygen partial pressure. Optical emission spectroscopy further confirms the increase in the oxygen negative ion density, along with a decrease in the argon positive ion density under the same discharge conditions. The relative negative ion concentration values measured by ion acoustic waves are compared with those measured by a single Langmuir probe, and a similarity in the results obtained by both techniques is observed.

  10. Numerical Analysis of Microdischarge Oxygen Plasma and Prediction of Ozone Production Efficiency

    NASA Astrophysics Data System (ADS)

    Kawano, Satoyuki; Misaka, Takashi

    In this research, numerical simulation of oxygen plasma produced by dielectric barrier discharge (DBD) is made as a basic research for the application of bioprocesses such as sterilization. Numerical simulation is based on an appropriate modeling of microdischarges including 9 kinds of species and 54 chemical reactions. Behavior of the oxygen plasma is analyzed by finite difference method in two-dimensional computational region. The detailed characteristics of filamentous discharge formed between parallel dielectric surfaces which cover the electrodes are investigated. The qualitative tendency of the discharge formation process agrees with the previous experimental observation. Ozone production efficiency (OPE) is obtained and compared with experimental results. Dependency of reduced electric field E/n on OPE is investigated by comparing the numerical results with previous experimental results by other researcher, where E/n is the ratio of electric field EE to number density n of neutral molecule in the gas. It is confirmed that the present numerical simulation has practically enough accuracy for the evaluation of the OPE to optimize the oxygen plasma sterilization devices.

  11. Double Langmuir frequency radiation due to transformation processes in turbulent plasma

    NASA Astrophysics Data System (ADS)

    Pavlenko, V. N.; Panchenko, V. G.; Beloshenko, N. A.

    2015-04-01

    We investigate the transformation process of longitudinal Langmuir wave into the transverse electromagnetic wave in turbulent plasma subjected to an upper hybrid pump. The case, when upper hybrid pump wave decays into daughter and ion - sound waves is considered. The transformation of the Langmuir wave into electromagnetic one is considered as the possible mechanism of energy radiation from the plasma. It is shown that the frequency of such radiation is chosen to be near double electron Langmuir frequency 2ωpe . These results give us the possibility to explain the nature of radiation from the laboratory and cosmic plasmas (particularly, from the solar crown).

  12. Low Frequency Plasma Turbulence as a Source of Clutter in Surveillance and Communication (Postprint)

    DTIC Science & Technology

    2013-08-01

    excited by plasma flows with velocity shear, whereas interchange or flute type oscillations in magnetized plasma are associated with Rayleigh-Taylor type...turbulence. Lower-hybrid type density irregularities are excited by plasma flows with velocity shear, whereas interchange or flute type oscillations...where  is the frequency of the flute mode and 0zi i ZeB m c  is the cyclotron frequency of the ion with charge Z and mass i pm m , with pm

  13. The effect of dielectric top lids on materials processing in a low frequency inductively coupled plasma (LF-ICP) reactor

    NASA Astrophysics Data System (ADS)

    Lim, J. W. M.; Chan, C. S.; Xu, L.; Xu, S.

    2014-08-01

    The advent of the plasma revolution began in the 1970's with the exploitation of plasma sources for anisotropic etching and processing of materials. In recent years, plasma processing has gained popularity, with research institutions adopting projects in the field and industries implementing dry processing in their production lines. The advantages of utilizing plasma sources would be uniform processing over a large exposed surface area, and the reduction of toxic emissions. This leads to reduced costs borne by manufacturers which could be passed down as consumer savings, and a reduction in negative environmental impacts. Yet, one constraint that plagues the industry would be the control of contaminants in a plasma reactor which becomes evident when reactions are conducted in a clean vacuum environment. In this work, amorphous silicon (a-Si) thin films were grown on glass substrates in a low frequency inductively coupled plasma (LF-ICP) reactor with a top lid made of quartz. Even though the chamber was kept at high vacuum ( 10-4 Pa), it was evident through secondary ion mass spectroscopy (SIMS) and Fourier-transform infra-red spectroscopy (FTIR) that oxygen contaminants were present. With the aid of optical emission spectroscopy (OES) the contaminant species were identified. The design of the LF-ICP reactor was then modified to incorporate an Alumina (Al2O3) lid. Results indicate that there were reduced amounts of contaminants present in the reactor, and that an added benefit of increased power transfer to the plasma, improving deposition rate of thin films was realized. The results of this study is conclusive in showing that Al2O3 is a good alternative as a top-lid of an LF-ICP reactor, and offers industries a solution in improving quality and rate of growth of thin films.

  14. Morphological evolution of self-deposition Bi2Se3 nanosheets by oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Jia, Guozhi; Wu, Zengna; Wang, Peng; Yao, Jianghong; Chang, Kai

    2016-02-01

    Bi2Se3 nanosheets were successfully synthesized by a microwave-assisted approach in the presence of polyvinylpyrroli done at a temperature of 180 °C for 2 h. The thin film was prepared on a silicon wafer via a self-deposition process in a Bi2Se3 nanosheet ink solution using the evaporation-induced self-assembly method. The structure and morphology of the obtained products were characterized by X-ray diffraction, scanning electron microscopy (SEM), x-ray photoelectron spectroscopy, and Raman spectroscopy. The highly uniform Bi2Se3 particles could be formed by controlling the oxygen plasma treatment time. After the plasma pretreatment from 10 to 20 s, the surface of Bi2Se3 film evolved from the worm-like structure to particles. The highly uniform thin film was formed on further increasing the plasma treatment time, which is consistent with the observed SEM results. Several important processes can result in the morphological evolution of Bi2Se3 nanosheets: (1) formation of Bi2Se3 oxide layer; (2) self-assembly of oxide nanoparticles under the action of high-energy oxygen plasma; and (3) electrostatic interaction and etching mechanism.

  15. Tunable electrical properties of multilayer HfSe2 field effect transistors by oxygen plasma treatment.

    PubMed

    Kang, Moonshik; Rathi, Servin; Lee, Inyeal; Li, Lijun; Khan, Muhammad Atif; Lim, Dongsuk; Lee, Yoontae; Park, Jinwoo; Yun, Sun Jin; Youn, Doo-Hyeb; Jun, Chungsam; Kim, Gil-Ho

    2017-01-26

    HfSe2 field effect transistors are systematically studied in order to selectively tune their electrical properties by optimizing layer thickness and oxygen plasma treatment. The optimized plasma-treated HfSe2 field effect transistors showed a high on/off ratio improvement of four orders of magnitude, from 27 to 10(5), a field effect mobility increase from 2.16 to 3.04 cm(2) V(-1) s(-1), a subthreshold swing improvement from 30.6 to 4.8 V dec(-1), and a positive threshold voltage shift between depletion mode and enhancement mode, from -7.02 to 11.5 V. The plasma-treated HfSe2 photodetector also demonstrates a reasonable photoresponsivity from the visible to the near-infrared region of light.

  16. Modelling chemical reactions in dc plasma inside oxygen bubbles in water

    NASA Astrophysics Data System (ADS)

    Takeuchi, N.; Ishii, Y.; Yasuoka, K.

    2012-02-01

    Plasmas generated inside oxygen bubbles in water have been developed for water purification. Zero-dimensional numerical simulations were used to investigate the chemical reactions in plasmas driven by dc voltage. The numerical and experimental results of the concentrations of hydrogen peroxide and ozone in the solution were compared with a discharge current between 1 and 7 mA. Upon increasing the water vapour concentration inside bubbles, we saw from the numerical results that the concentration of hydrogen peroxide increased with discharge current, whereas the concentration of ozone decreased. This finding agreed with the experimental results. With an increase in the discharge current, the heat flux from the plasma to the solution increased, and a large amount of water was probably vaporized into the bubbles.

  17. Effects of temperature and molecular oxygen on the use of atmospheric pressure plasma as a novel method for insect control.

    PubMed

    Donohue, Kevin V; Bures, Brian L; Bourham, Mohamed A; Roe, R Michael

    2008-04-01

    Helium atmospheric pressure plasma discharge (APPD) was previously shown to have insecticidal activity with a possible site of action on the insect nervous, neuromuscular system, or both. In the current study, methods to increase the insecticidal activity of plasma by using increased APPD temperature and the introduction of molecular oxygen were investigated for the first time. An increase in the helium plasma temperature from 37 to 50 degrees C increased the insecticidal activity of plasma for the control of the German cockroach, Blattella germanica (L.); western flower thrips, Frankliniella occidentalis (Pergande); and citrus mealybug, Planococcus citri (Risso). This increase in activity could not be explained by the increase in air temperature alone, and it suggests that the enhanced insecticidal activity resulted from increased ionization of the APPD and ion bombardment of the insect. Emission spectroscopy showed that the introduction of 0.5% oxygen into helium plasma produced ionic molecular oxygen at 559.7 and 597.3 nm. The introduction of oxygen to the APPD greatly increased the insecticidal activity of plasma for the citrus mealybug but not the German cockroach or western flower thrips. For the mealybug as an example, the mortality of a 60-s exposure of 37 degrees C helium plasma was 0% at 1 h after exposure and 100% under the same conditions after the introduction of oxygen. It seems that increases in temperature and the introduction of oxygen even at low levels can increase the insecticidal activity of plasma to varying degrees depending on the insect species. The symptomology of cockroach death for both hot plasma and plasma containing trace amounts of molecular oxygen continued to suggest that the site of action of APPD is the insect nervous system, neuromuscular system, or both.

  18. A Study of Impedance Relationships in Dual Frequency PECVD Process Plasma

    NASA Astrophysics Data System (ADS)

    Keil, Douglas; Augustyniak, Edward; Sakiyama, Yukinori; Pecvd/Ald Team

    2016-09-01

    Commercial plasma process reactors are commonly operated with a very limited suite of on-board plasma diagnostics. However, as process demands advance so has the need for detailed plasma monitoring and diagnosis. The VI probe is one of the few instruments commonly available for this task. We present a study of voltage, current, impedance and phase trends acquired by off-the-shelf VI probes in Dual Frequency (DF) 400 kHz/13.56MHz capacitively-coupled plasma (CCP) as typically used for Plasma Enhanced Chemical Vapor Deposition (PECVD). These plasmas typically operate at pressures from 1 to 5 Torr and at RF power levels of 3 W/cm2. Interpretation of DF VI probe impedance trends is challenging. Non-linear interactions are known to exist in plasma impedance scaling with low and high frequency RF power. Simple capacitive sheath models typically do not simultaneously reproduce the impedance observed at each drive frequency. This work will compare VI probe observed DF CCP impedance tends with plasma fluid simulation. Also explored is the agreement seen with sheath models presently available in the literature. Prospects for the creation of useful equivalent circuit models is also discussed.

  19. The effect of UV radiation from oxygen and argon plasma on the adhesion of organosilicon coatings on polypropylene

    NASA Astrophysics Data System (ADS)

    Jaritz, M.; Behm, H.; Hopmann, Ch; Kirchheim, D.; Mitschker, F.; Awakowicz, P.; Dahlmann, R.

    2017-01-01

    The influence of ultraviolet (UV) radiation from oxygen and argon pretreatment plasmas on a plastic substrate has not been fully understood yet. In particular, its influence on the adhesion properties has not been sufficiently researched so far. This paper addresses this issue by comparing the bond strength of a plasmapolymerized silicon organic coating (SiO x C y H z ) on polypropylene (PP) after oxygen and argon plasma pretreatment and pretreatment by UV radiation emitted by the same plasmas. The UV radiation is isolated from the other species from the plasma by means of a magnesium fluoride (MgF2) optical filter. It could be shown that UV radiation originating from an oxygen plasma has a significant impact on both substrate surface chemistry and coating adhesion. The same maximum bond strength enhancement can be reached by pretreating the polypropylene surface either with pulsed oxygen plasma, or with only the UV radiation from this oxygen plasma. Also, similar surface chemistry and topography modifications are induced. For argon plasma no significant influence of its UV radiation on the substrate could be observed in this study.

  20. Frequency-duration analysis of dissolved-oxygen concentrations in two southwestern Wisconsin streams

    USGS Publications Warehouse

    Greb, Steven R.; Graczyk, David J.

    2007-01-01

    Historically, dissolved-oxygen (DO) data have been collected in the same manner as other water-quality constituents, typically at infrequent intervals as a grab sample or an instantaneous meter reading. Recent years have seen an increase in continuous water-quality monitoring with electronic dataloggers. This new technique requires new approaches in the statistical analysis of the continuous record. This paper presents an application of frequency-duration analysis to the continuous DO records of a cold and a warm water stream in rural southwestern Wisconsin. This method offers a quick, concise way to summarize large time-series data bases in an easily interpretable manner. Even though the two streams had similar mean DO concentrations, frequency-duration analyses showed distinct differences in their DO-concentration regime. This type of analysis also may be useful in relating DO concentrations to biological effects and in predicting low DO occurrences.

  1. Self-consistent modeling of radio-frequency plasma generation in stellarators

    SciTech Connect

    Moiseenko, V. E. Stadnik, Yu. S.; Lysoivan, A. I.; Korovin, V. B.

    2013-11-15

    A self-consistent model of radio-frequency (RF) plasma generation in stellarators in the ion cyclotron frequency range is described. The model includes equations for the particle and energy balance and boundary conditions for Maxwell’s equations. The equation of charged particle balance takes into account the influx of particles due to ionization and their loss via diffusion and convection. The equation of electron energy balance takes into account the RF heating power source, as well as energy losses due to the excitation and electron-impact ionization of gas atoms, energy exchange via Coulomb collisions, and plasma heat conduction. The deposited RF power is calculated by solving the boundary problem for Maxwell’s equations. When describing the dissipation of the energy of the RF field, collisional absorption and Landau damping are taken into account. At each time step, Maxwell’s equations are solved for the current profiles of the plasma density and plasma temperature. The calculations are performed for a cylindrical plasma. The plasma is assumed to be axisymmetric and homogeneous along the plasma column. The system of balance equations is solved using the Crank-Nicholson scheme. Maxwell’s equations are solved in a one-dimensional approximation by using the Fourier transformation along the azimuthal and longitudinal coordinates. Results of simulations of RF plasma generation in the Uragan-2M stellarator by using a frame antenna operating at frequencies lower than the ion cyclotron frequency are presented. The calculations show that the slow wave generated by the antenna is efficiently absorbed at the periphery of the plasma column, due to which only a small fraction of the input power reaches the confinement region. As a result, the temperature on the axis of the plasma column remains low, whereas at the periphery it is substantially higher. This leads to strong absorption of the RF field at the periphery via the Landau mechanism.

  2. Effect of oxygen plasma treatment on CdSe/CdZnS quantum-dot light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Cho, Nam-Kwang; Yu, Jae-woong; Kim, Young Heon; Kang, Seong Jun

    2014-03-01

    Red-light-emitting diodes (LEDs) were fabricated using CdSe/CdZnS quantum dots (QDs). During the device fabrication process, the oxygen plasma treatment of the indium-tin oxide (ITO) surface was performed to improve the interfacial contact between the ITO anode and the hole injection layer. The device showed red emission at 622 nm, which was consistent with the dimensions of the QDs (band gap: 1.99 eV). The luminance was 108.77 cd/m2 and the current density was 230.2 mA/cm2 at an operating voltage of 7 V, when the oxygen plasma treatment was performed on the ITO surface. The luminance showed 207% improvement compared with that of LEDs fabricated without oxygen plasma treatment. These results suggested that the oxygen plasma treatment of the ITO surface improved the contact between ITO and PEDOT:PSS, and that the light emitting intensity was markedly improved.

  3. Effect of dual frequency rf power in an inductively coupled plasma

    NASA Astrophysics Data System (ADS)

    Kim, Ju-Ho; Lee, Ho-Won; Kim, Tae Woo; Chung, Chin-Wook

    2016-09-01

    Dual frequency inductively coupled plasma discharge is investigated. Dual RF power is applied independently to each antenna (inner and outer coil), and the electron energy distribution functions (EEDFs) are measured using a RF compensated Langmuir probe. As the ratio of low frequency power (Plow) and high frequency power (Phigh) is changed, the variation of EEDF is observed. When Plow is higher than Phigh, the low energy electrons effectively heated compared to the case when Plow is comparable to Phigh. This difference in the shape of the EEDF can be understood by correlation between the driving frequency and the collision frequency.

  4. Surface cleaning for enhanced adhesion to packaging surfaces: Effect of oxygen and ammonia plasma

    SciTech Connect

    Gaddam, Sneha; Dong, Bin; Driver, Marcus; Kelber, Jeffry; Kazi, Haseeb

    2015-03-15

    The effects of direct plasma chemistries on carbon removal from silicon nitride (SiN{sub x}) and oxynitride (SiO{sub x}N{sub y}) surfaces have been studied by in-situ x-ray photoelectron spectroscopy (XPS) and ex-situ contact angle measurements. The data indicate that O{sub 2} and NH{sub 3} capacitively coupled plasmas are effective at removing adventitious carbon from silicon nitride (SiN{sub x}) and Si oxynitride (SiO{sub x}N{sub y}) surfaces. O{sub 2} plasma treatment results in the formation of a silica overlayer. In contrast, the exposure to NH{sub 3} plasma results in negligible additional oxidation of the SiN{sub x} or SiO{sub x}N{sub y} surface. Ex-situ contact angle measurements show that SiN{sub x} and SiO{sub x}N{sub y} surfaces exposed to oxygen plasma are initially more hydrophilic than surfaces exposed to NH{sub 3} plasma, indicating that the O{sub 2} plasma-induced SiO{sub 2} overlayer is highly reactive toward ambient. At longer ambient exposures (≳10 h), however, surfaces treated by either O{sub 2} or NH{sub 3} plasma exhibit similar steady state contact angles, correlated with rapid uptake of adventitious carbon, as determined by XPS. Surface passivation by exposure to molecular hydrogen prior to ambient exposure significantly retards the increase in contact angle upon exposure to ambient. The results suggest a practical route to enhancing the time available for effective bonding to surfaces in microelectronics packaging applications.

  5. Magnetoresistive polyaniline-silicon carbide metacomposites: plasma frequency determination and high magnetic field sensitivity.

    PubMed

    Gu, Hongbo; Guo, Jiang; Khan, Mojammel Alam; Young, David P; Shen, T D; Wei, Suying; Guo, Zhanhu

    2016-07-20

    The Drude model modified by Debye relaxation time was introduced to determine the plasma frequency (ωp) in the surface initiated polymerization (SIP) synthesized β-silicon carbide (β-SiC)/polyaniline (PANI) metacomposites. The calculated plasma frequency for these metacomposites with different loadings of β-SiC nanoparticles was ranging from 6.11 × 10(4) to 1.53 × 10(5) rad s(-1). The relationship between the negative permittivity and plasma frequency indicates the existence of switching frequency, at which the permittivity was changed from negative to positive. More interestingly, the synthesized non-magnetic metacomposites, observed to follow the 3-dimensional (3-D) Mott variable range hopping (VRH) electrical conduction mechanism, demonstrated high positive magnetoresistance (MR) values of up to 57.48% and high MR sensitivity at low magnetic field regimes.

  6. Reactivity and analytical performance of oxygen as cell gas in inductively coupled plasma tandem mass spectrometry

    NASA Astrophysics Data System (ADS)

    Virgilio, Alex; Amais, Renata S.; Amaral, Clarice D. B.; Fialho, Lucimar L.; Schiavo, Daniela; Nóbrega, Joaquim A.

    2016-12-01

    The reactivity and analytical performance of O2 as cell gas in inductively coupled plasma tandem mass spectrometry was investigated. Selected analytes in a wide mass range were divided in three groups according to their reactivity: G1 represents elements with high oxygen affinity (Ce, La, P, Sc, Ti, and Y), G2 contains elements that may partially react with oxygen (As, Ba, Mo, Si, Sr, and V), and G3 comprises elements expected to be less reactive towards oxygen (Al, Bi, Cu, Mg, Pb, and Pd). On-mass and mass-shift modes were evaluated by monitoring atomic and metal oxide ions, respectively. Analytical signal profiles, oxide percentages, sensitivities and limits of detection for oxygen flow rates varying from 0.1 to 1.0 mL min- 1 were also studied. Group 1 elements plus As and V presented better sensitivities and LODs when measuring oxides, which were the major species for all flow rates evaluated. Molybdenum and Si oxides presented intermediate behavior and MoO fraction was up to 47% and limit of detection was the same as that obtained in on-mass mode. For others G2 and G3 elements, on-mass mode presented higher sensitivity and better LODs, with estimated oxide contents lower than 10%. In most cases, increasing oxygen flow rates led to lower sensitivities and worse LODs.

  7. Particle formation and its control in dual frequency plasma etching reactors

    SciTech Connect

    Kim, Munsu; Cheong, Hee-Woon; Whang, Ki-Woong

    2015-07-15

    The behavior of a particle cloud in plasma etching reactors at the moment when radio frequency (RF) power changes, that is, turning off and transition steps, was observed using the laser-light-scattering method. Two types of reactors, dual-frequency capacitively coupled plasma (CCP) and the hybrid CCP/inductively coupled plasma (ICP), were set up for experiments. In the hybrid CCP/ICP reactor (hereafter ICP reactor), the position and shape of the cloud were strongly dependent on the RF frequency. The particle cloud becomes larger and approaches the electrode as the RF frequency increases. By turning the lower frequency power off later with a small delay time, the particle cloud is made to move away from the electrode. Maintaining lower frequency RF power only was also helpful to reduce the particle cloud size during this transition step. In the ICP reactor, a sufficient bias power is necessary to make a particle trap appear. A similar particle cloud to that in the CCP reactor was observed around the sheath region of the lower electrode. The authors can also use the low-frequency effect to move the particle cloud away from the substrate holder if two or more bias powers are applied to the substrate holder. The dependence of the particle behavior on the RF frequencies suggests that choosing the proper frequency at the right moment during RF power changes can reduce particle contamination effectively.

  8. Radio-frequency Ar plasma treatment on muga silk fiber: correlation between physicochemical and surface morphology

    NASA Astrophysics Data System (ADS)

    Gogoi, Dolly; Chutia, Joyanti; Choudhury, Arup Jyoti; Pal, Arup Ratan; Patil, Dinkar

    2012-11-01

    Radio-frequency (RF) Ar plasma treatment is carried out on natural muga silk fibers in a capacitively coupled plasma reactor. The physical and thermal properties of the muga fibers are investigated at an RF power of 20 W and in the treatment time range of 5 to 20 min. The virgin and plasma-treated muga fibers are characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The effect of Ar plasma treatment can be observed only on the outermost layer of the muga fibers without any significant variation in their bulk and thermal properties, as supported by differential scanning calorimetry and thermogravimetric analysis. Improvement in tensile strength and hydrophobicity of the plasma-treated muga fibers is observed at lower treatment time and RF power. Attempts are made to correlate the properties of the plasma-treated muga fibers with their surface chemistry and surface morphologies.

  9. Heating of a Magnetized High Density Hydrogen Plasma Column Around the ICR Frequency

    NASA Astrophysics Data System (ADS)

    Graswinckel, M. F.; Guadamuz, S.; Koch, R.; Maggiora, R.; Van De Pol, M.; Vietti, G.; Van Rooij, G.

    2011-12-01

    A single and double loop antenna system are investigated in the ICR frequency range (5-25 MHz) to enable control of the plasma temperature in a 1-10 cm diameter, 1020 m-3 hydrogen plasma column in B = 0.8T Wave propagation is evaluated on basis of damping lengths derived from the dispersion relation. The antenna is numerically analyzed with the TOPCYL code. Simulation results are compared with measured loading resistances and good agreement was found for the vacuum and saltwater column cases. Hydrogen plasma loading resistances determined from network analyzer measurements are typically higher than those predicted from simulation. This points to coupling of RF power to additional loss mechanisms. High RF power operation (1 kW) of the antenna increased the power deposited on the plasma endplate and accelerated the plasma, but the plasma temperature near the endplate remained constant.

  10. Plasma decay in high-voltage nanosecond discharges in oxygen-containing mixtures

    SciTech Connect

    Anokhin, E. M.; Popov, M. A.; Kochetov, I. V.; Aleksandrov, N. L.; Starikovskii, A. Yu.

    2016-01-15

    Plasma decay in high-voltage nanosecond discharges in CO{sub 2}: O{sub 2} and Ar: O{sub 2} mixtures at room gas temperature and a pressure of 10 Torr is studied experimentally and theoretically. The time dependence of the electron density during plasma decay is measured using microwave interferometry. The time evolution of the charged particle density, ion composition, and electron temperature is simulated numerically. It is shown that, under the given conditions, the discharge plasma is dominated for the most time by O{sub 2}{sup +} ions and plasma decay is determined by dissociative and three-body electron−ion recombination. As in the previous studies performed for air and oxygen plasmas, agreement between measurements and calculations is achieved only under the assumption that the rate of three-body recombination of molecular ions is much greater than that for atomic ions. The values of the rate constant of three-body recombination of electrons with O{sub 2}{sup +} ions in a wide range of electron temperatures (500–5500 K), as well as for thermal (300 K) electrons, are obtained by processing the experimental results.

  11. Reactive oxygen species in plasma against E. coli cells survival rate

    NASA Astrophysics Data System (ADS)

    Zhou, Ren-Wu; Zhang, Xian-Hui; Zong, Zi-Chao; Li, Jun-Xiong; Yang, Zhou-Bin; Liu, Dong-Ping; Yang, Si-Ze

    2015-08-01

    In this paper, we report on the contrastive analysis of inactivation efficiency of E. coli cells in solution with different disinfection methods. Compared with the hydrogen peroxide solution and the ozone gas, the atmospheric-pressure He plasma can completely kill the E. coli cells in the shortest time. The inactivation efficiency of E. coli cells in solution can be well described by using the chemical reaction rate model. X-ray photoelectron spectroscopy (XPS) analysis shows that the C-O or C=O content of the inactivated E. coli cell surface by plasma is predominantly increased, indicating the quantity of oxygen-containing species in plasma is more than those of two other methods, and then the C-C or C-H bonds can be broken, leading to the etching of organic compounds. Analysis also indicates that plasma-generated species can play a crucial role in the inactivation process by their direct reactions or the decompositions of reactive species, such as ozone into OH radicals in water, then reacting with E. coli cells. Project supported by the Natural Science Foundation of Fujian Province, China (Grant No. 2014J01025), the National Natural Science Foundation of China (Grant No. 11275261), and the Funds from the Fujian Provincial Key Laboratory for Plasma and Magnetic Resonance, China.

  12. Experimental study of a very high frequency, 162 MHz, segmented electrode, capacitively coupled plasma discharge

    NASA Astrophysics Data System (ADS)

    Sirse, Nishant; Harvey, Cleo; Gaman, Cezar; Ellingboe, Bert

    2016-09-01

    Radio-frequency capacitively coupled plasma (CCP) discharge operating at a very high frequency, 30-300 MHz, offers many advantages over standard 13.56 MHz CCP. However, there is a limited flexibility on the choice of driving frequency and substrate size due to plasma non-uniformity caused by the standing wave effect and edge effect. To overcome this issue segmented electrode CCP's are proposed and researched. Despite its numerous advantages the power coupling mechanism and plasma chemistry in this type of discharge are not fully understood due to lack of experimental data. In this paper, we present the experimental study of a segmented electrode, 3x4 tile array (10x10 cm square tile with 1 cm tile-to-tile separation), CCP discharge driven at 162 MHz. We measured plasma uniformity and gas temperature using hairpin probe and optical emission spectroscopy respectively. A homemade RF compensated Langmuir probe is employed to measure the Electron Energy Distribution Function (EEDF) by second harmonic technique. Energy resolved quadrupole mass spectrometer is utilized to measure the ion energy distribution. Discharge/plasma properties are investigated for several operating conditions and for power coupling mode in both washer board and checker board configuration. The experimental results show that the uniform plasma density can be maintained over a large area along with highly non-equilibrium condition to produce unique gas phase plasma chemistry.

  13. Comparison of Calculated Plasma Mode Frequencies with Experiment

    NASA Astrophysics Data System (ADS)

    Tobler, Samuel; Peterson, Bryan G.; Hart, Grant W.

    2004-11-01

    We have measured the diocotron and Trivelpiece-Gould mode frequencies, radial density profile and central temperature in a long (0.6 m), cylindrical Malmberg-Penning electron trap at four different magnetic field strengths. The total particle count varied by a factor of 10 and the magnetic field varied by a factor of 3.5. The temperatures were fairly constant. Using an equilibrium code (EQUILSOR), a 2-D particle-in-cell code (RATTLE), and a 3-D particle-in-cell code (INFERNO) we have calculated the frequencies corresponding to the experimental conditions. We will discuss the limitations of the codes and the conditions in which they agree with experimental results.

  14. Escape and trapping of low-frequency gravitationally lensed rays by compact objects within plasma

    NASA Astrophysics Data System (ADS)

    Rogers, Adam

    2017-02-01

    We consider the gravitational lensing of rays emitted by a compact object (CO) within a distribution of plasma with power-law density ∝r-h. For the simplest case of a cloud of spherically symmetric cold non-magnetized plasma, the diverging effect of the plasma and the converging effect of gravitational lensing compete with one another. When h < 2, the plasma effect dominates over the vacuum Schwarzschild curvature, potentially shifting the radius of the unstable circular photon orbit outside the surface of the CO. When this occurs, we define two relatively narrow radio frequency bands in which plasma effects are particularly significant. Rays in the escape window have ω0 < ω ≤ ω+ and are free to propagate to infinity from the CO surface. To a distant observer, the visible portion of the CO surface appears to shrink as the observed frequency is reduced, and vanishes entirely at ω0, in excess of the plasma frequency at the CO surface. We define the anomalous propagation window for frequencies ω- < ω ≤ ω0. Rays emitted from the CO surface within this frequency range are dominated by optical effects from the plasma and curve back to the surface of the CO, effectively cloaking the star from distant observers. We conclude with a study of neutron star (NS) compactness ratios for a variety of nuclear matter equations of state (EoS). For h = 1, NSs generated from stiff EoS should display significant frequency dependence in the EW, and lower values of h with softer EoS can also show these effects.

  15. Bacterial adhesion to orthopaedic implant materials and a novel oxygen plasma modified PEEK surface.

    PubMed

    Rochford, E T J; Poulsson, A H C; Salavarrieta Varela, J; Lezuo, P; Richards, R G; Moriarty, T F

    2014-01-01

    Despite extensive use of polyetheretherketone (PEEK) in biomedical applications, information about bacterial adhesion to this biomaterial is limited. This study investigated Staphylococcus aureus and Staphylococcus epidermidis adhesion to injection moulded and machined PEEK OPTIMA(®) using a custom-built adhesion chamber with medical grade titanium and Thermanox for comparison. Additionally, bacterial adhesion to a novel oxygen plasma modified PEEK was also investigated in both a pre-operative model in physiological saline, and additionally in a post-operative model in human blood plasma. In the pre-operative model, the rougher machined PEEK had a significantly greater number of adherent bacteria compared to injection moulded PEEK. Bacterial adhesion to titanium and Thermanox was similar. Oxygen plasma surface modification of PEEK did not lead to a significant change in bacterial adhesion in the pre-operative contamination model, despite observed changes in surface characteristics. In the post-operative contamination model, S. aureus adhesion was increased from 5×10(5) CFU cm(-2) to approximately 1.3×10(7) CFU cm(-2) on the modified surfaces due to differential protein adhesion during the conditioning period. However, S. epidermidis adhesion to modified PEEK was less than to unmodified PEEK in the post-operative model. These results illustrate the importance of testing bacterial adhesion of several strains in both a pre-operative and post-operative, clinically relevant bacterial contamination model.

  16. Dynamic properties of ionospheric plasma turbulence driven by high-power high-frequency radiowaves

    NASA Astrophysics Data System (ADS)

    Grach, S. M.; Sergeev, E. N.; Mishin, E. V.; Shindin, A. V.

    2016-11-01

    A review is given of the current state-of-the-art of experimental studies and the theoretical understanding of nonlinear phenomena that occur in the ionospheric F-layer irradiated by high-power high-frequency ground-based transmitters. The main focus is on the dynamic features of high-frequency turbulence (plasma waves) and low-frequency turbulence (density irregularities of various scales) that have been studied in experiments at the Sura and HAARP heating facilities operated in temporal and frequency regimes specially designed with consideration of the characteristic properties of nonlinear processes in the perturbed ionosphere using modern radio receivers and optical instruments. Experimental results are compared with theoretical turbulence models for a magnetized collisional plasma in a high-frequency electromagnetic field, allowing the identification of the processes responsible for the observed features of artificial ionospheric turbulence.

  17. Dynamic properties of ionospheric plasma turbulence driven by high-power high-frequency radiowaves

    NASA Astrophysics Data System (ADS)

    Grach, S. M.; Sergeev, E. N.; Mishin, E. V.; Shindin, A. V.

    2017-02-01

    A review is given of the current state-of-the-art of experimental studies and the theoretical understanding of nonlinear phenomena that occur in the ionospheric F-layer irradiated by high-power high-frequency ground-based transmitters. The main focus is on the dynamic features of high-frequency turbulence (plasma waves) and low-frequency turbulence (density irregularities of various scales) that have been studied in experiments at the Sura and HAARP heating facilities operated in temporal and frequency regimes specially designed with consideration of the characteristic properties of nonlinear processes in the perturbed ionosphere using modern radio receivers and optical instruments. Experimental results are compared with theoretical turbulence models for a magnetized collisional plasma in a high-frequency electromagnetic field, allowing the identification of the processes responsible for the observed features of artificial ionospheric turbulence.

  18. Optical Tamm states above the bulk plasma frequency at a Bragg stack/metal interface

    NASA Astrophysics Data System (ADS)

    Brand, S.; Kaliteevski, M. A.; Abram, R. A.

    2009-02-01

    We demonstrate theoretically that surface-plasmon polaritons, a form of optical Tamm state, can occur at the interface between a metal and a Bragg reflector at frequencies above the bulk plasma frequency of the metal. The frequencies of the excitations are within the photonic band gap of the Bragg reflector which provides the required evanescent decay on that side of the interface. At finite in-plane wave vector, the low value of the permittivity of the metal above its plasma frequency can lead to an imaginary normal wave vector component in the metal, which provides the localization on the other side of the interface. It is proposed that the necessary conditions can be realized using a GaAs/AlAs Bragg stack coated with a suitable conducting metal oxide having a bulk plasma frequency of 1 eV, but the concept is valid for other systems given an appropriate plasma frequency and photonic band-gap structure. The dispersion relations of the plasmon polaritons in the structures considered are calculated for both possible polarizations, and it is shown how the excitations result in distinct features in the predicted reflectivity spectra.

  19. Plasma ignition schemes for the SNS radio-frequency driven H- source

    SciTech Connect

    Schenkel, T.; Staples, J.W.; Thomae, W.; Reijonen, J.; Gough, R.A.; Leung, K.N.; Keller, R.

    2001-09-06

    The H{sup -} ion source for the Spallation Neutron Source (SNS) is a cesiated, radio-frequency driven (2 MHz) multicusp volume source which operates at a duty cycle of 6% (1 ms pulses and 60 Hz). In pulsed RF driven plasma sources, ignition of the plasma affects the stability of source operation and the antenna lifetime. We are reporting on investigations of different ignition schemes, based on secondary electron generation in the plasma chamber by UV light, a hot filament, a low power RF plasma (cw, 13.56 MHz), as well as source operation solely with the high power (40 kW) 2 MHz RF. We find that the dual frequency, single antenna scheme is most attractive for the operating conditions of the SNS H{sup -} source.

  20. Detailed plasma potential measurements in a radio-frequency expanding plasma obtained from various electrostatic probes

    SciTech Connect

    Lafleur, T.; Charles, C.; Boswell, R. W.

    2009-04-15

    On-axis plasma potential measurements have been made with an emissive probe in a low pressure (0.044 Pa) rf expanding plasma containing an ion beam. The beam is detected with a retarding field energy analyzer (RFEA), and is seen to disappear at high pressure (0.39 Pa). The emissive probe measurements are in very good agreement with corresponding measurements made with two separate RFEAs, and the results indicate that the floating potential of the strongly emitting probe gives an accurate measure of the plasma potential under the present conditions.

  1. Growth of MoO3 films by oxygen plasma assisted molecular beam epitaxy

    SciTech Connect

    Altman, Eric I.; Droubay, Timothy C.; Chambers, Scott A.

    2002-07-22

    The growth of MoO₃ films on SrLaAlO₄(0 0 1), a substrate lattice-matched to b-MoO , by oxygen plasma assisted molecular beam epitaxy was characterized using reflection high-energy electron diffraction (RHEED), X-ray photoelectron spectroscopy, Xray diffraction (XRD), and atomic force and scanning tunneling microscopies (AFM and STM).It was found that the flux of reactive oxygen species to the surface was not high enough to maintain the proper stoichiometry, even at the lowest measurable deposition rates. Therefore, the films were grown by depositing Mo in small increments and then allowing the Mo to oxidize. At 675 K, the films grew epitaxially but in a three-dimensional manner. XRD of films grown under these conditions revealed atetragonal structure that has not been previously observed in bulk MoO₃ samples.

  2. Increased Oxygen Recovery from Sabatier Systems Using Plasma Pyrolysis Technology and Metal Hydride Separation

    NASA Technical Reports Server (NTRS)

    Greenwood, Zachary W.; Abney, Morgan B.; Perry, Jay L.; Miller, Lee A.; Dahl, Roger W.; Hadley, Neal M.; Wambolt, Spencer R.; Wheeler, Richard R.

    2015-01-01

    State-of-the-art life support carbon dioxide (CO2) reduction technology is based on the Sabatier reaction where less than 50% of the oxygen required for the crew is recovered from metabolic CO2. The reaction produces water as the primary product and methane as a byproduct. Oxygen recovery is constrained by the limited availability of reactant hydrogen. This is further exacerbated when Sabatier methane (CH4) is vented as a waste product resulting in a continuous loss of reactant hydrogen. Post-processing methane with the Plasma Pyrolysis Assembly (PPA) to recover hydrogen has the potential to dramatically increase oxygen recovery and thus drastically reduce the logistical challenges associated with oxygen resupply. The PPA decomposes methane into predominantly hydrogen and acetylene. Due to the highly unstable nature of acetylene, a separation system is necessary to purify hydrogen before it is recycled back to the Sabatier reactor. Testing and evaluation of a full-scale Third Generation PPA is reported and investigations into metal hydride hydrogen separation technology is discussed.

  3. Frequency-resolved optical gating for characterization of VUV pulses using ultrafast plasma mirror switching.

    PubMed

    Itakura, Ryuji; Kumada, Takayuki; Nakano, Motoyoshi; Akagi, Hiroshi

    2015-05-04

    We propose and experimentally demonstrate a method for characterizing vacuum ultraviolet (VUV) pulses based on time-resolved reflection spectroscopy of fused silica pumped by an intense laser pulse. Plasma mirror reflection is used as an ultrafast optical switch, which enables us to measure frequency-resolved optical gating (FROG) traces. The VUV temporal waveform can be retrieved from the measured FROG trace using principal component generalized projections algorithm with modification. The temporal profile of the plasma mirror reflectivity is also extracted simultaneously.

  4. Equivalent circuit of radio frequency-plasma with the transformer model.

    PubMed

    Nishida, K; Mochizuki, S; Ohta, M; Yasumoto, M; Lettry, J; Mattei, S; Hatayama, A

    2014-02-01

    LINAC4 H(-) source is radio frequency (RF) driven type source. In the RF system, it is required to match the load impedance, which includes H(-) source, to that of final amplifier. We model RF plasma inside the H(-) source as circuit elements using transformer model so that characteristics of the load impedance become calculable. It has been shown that the modeling based on the transformer model works well to predict the resistance and inductance of the plasma.

  5. Electron-ion collision-frequency for x-ray Thomson scattering in dense plasmas

    SciTech Connect

    Faussurier, Gérald Blancard, Christophe

    2016-01-15

    Two methods are presented to calculate the electron-ion collision-frequency in dense plasmas using an average-atom model. The first one is based on the Kubo-Greenwood approach. The second one uses the Born and Lenard-Balescu approximations. The two methods are used to calculate x-ray Thomson scattering spectra. Illustrations are shown for dense beryllium and aluminum plasmas. Comparisons with experiment are presented in the case of an x-ray Thomson scattering spectrum.

  6. Nonlinear frequency shift in Raman backscattering and its implications for plasma diagnostics

    NASA Astrophysics Data System (ADS)

    Kaganovich, D.; Hafizi, B.; Palastro, J. P.; Ting, A.; Helle, M. H.; Chen, Y.-H.; Jones, T. G.; Gordon, D. F.

    2016-12-01

    Raman backscattered radiation of intense laser pulses in plasmas is investigated for a wide range of intensities relevant to laser wakefield acceleration. The weakly nonlinear dispersion relation for Raman backscattering predicts an intensity and density dependent frequency shift that is opposite to that suggested by a simple relativistic consideration. This observation has been benchmarked against experimental results, providing a novel diagnostic for laser-plasma interactions.

  7. Electron-ion collision-frequency for x-ray Thomson scattering in dense plasmas

    NASA Astrophysics Data System (ADS)

    Faussurier, Gérald; Blancard, Christophe

    2016-01-01

    Two methods are presented to calculate the electron-ion collision-frequency in dense plasmas using an average-atom model. The first one is based on the Kubo-Greenwood approach. The second one uses the Born and Lenard-Balescu approximations. The two methods are used to calculate x-ray Thomson scattering spectra. Illustrations are shown for dense beryllium and aluminum plasmas. Comparisons with experiment are presented in the case of an x-ray Thomson scattering spectrum.

  8. Improvement of the lifetime of radio frequency antenna for plasma generation

    SciTech Connect

    Reijonen, J.; Eardley, M.; Gough, R.; Keller, R.; Leung, K.; Thomae, R.; Pickard, D.; Williams, M. D.

    2000-02-01

    At Lawrence Berkeley National Laboratory different antenna protection schemes have been investigated for the radio frequency-driven multicusp ion source. It was found that the antenna lifetime can be greatly enhanced by an additional shielding, which consists of porcelain, quartz or boron nitride. Different antenna configurations and their influence on the plasma generation will be discussed. Antenna life time greater than 500 hours continuous wave operation has been demonstrated in hydrogen plasma using a novel quartz antenna design. (c)

  9. Spectroscopic Measurement of High-Frequency Electric Fields in the Interaction of Explosive Debris Plasma with Ambient, Magnetized Background Plasma

    NASA Astrophysics Data System (ADS)

    Bondarenko, Anton; Schaeffer, Derek; Everson, Erik; Clark, Eric; Vincena, Stephen; van Compernolle, Bart; Tripathi, Shreekrishna; Constantin, Carmen; Niemann, Chris

    2014-10-01

    The explosive expansion of dense, high-beta debris plasma into relatively tenuous, magnetized background plasma is relevant to a wide variety of astrophysical and space environments. Electric fields play a fundamental role in the coupling of momentum and energy from debris to background, and emission spectroscopy provides a powerful diagnostic for assessing electric fields via the Stark effect. A recent experiment utilizing a unique experimental platform at UCLA that combines the Large Plasma Device and the Raptor laser facility has investigated the super-Alfvénic, quasi-perpendicular expansion of a laser-produced carbon (C) debris plasma through a preformed, ambient, magnetized helium (He) background plasma via emission spectroscopy. Spectral profiles of the He II 468.6 nm line have been analyzed via single-mode and multi-mode time-dependent Stark broadening models for hydrogen-like ions, yielding large magnitude (~100 kV/cm), high-frequency (~100 GHz) electric fields. The measurements suggest the development of an electron beam-plasma instability, and a simple instability saturation model demonstrates that the measured electric field magnitudes are feasible under the experimental conditions.

  10. Two-dimensional profile measurement of plasma parameters in radio frequency-driven argon atmospheric pressure plasma jet

    SciTech Connect

    Seo, B. H.; Kim, J. H.; Kim, D. W.; You, S. J.

    2015-09-15

    The two-dimensional profiles of the electron density, electron temperature, neutral translational temperature, and molecular rotational temperature are investigated in an argon atmospheric pressure plasma jet, which is driven by the radio frequency of 13.56 MHz by means of the laser scattering methods of Thomson, Rayleigh, and Raman. All measured parameters have maximum values at the center of the discharge and decrease toward the plasma edge. The results for the electron temperature profile are contrary to the results for the microwave-driven plasma. From our experimental results, the profiles of the plasma parameters arise from the radial contraction of plasmas and the time averaged profile of the electric field, which is obtained by a microwave simulation performed under identical conditions to the plasma jet. In the case of the neutral temperature, a higher translational temperature than the rotational temperature is measured, and its discrepancy is tentatively explained in terms of the low ion-neutral charge exchange rate and the additional degrees of freedom of the molecules. The description of our experimental results and the underlying physics are addressed in detail.

  11. Low temperature synthesis of silicon quantum dots with plasma chemistry control in dual frequency non-thermal plasmas.

    PubMed

    Sahu, Bibhuti Bhusan; Yin, Yongyi; Han, Jeon Geon; Shiratani, Masaharu

    2016-06-21

    The advanced materials process by non-thermal plasmas with a high plasma density allows the synthesis of small-to-big sized Si quantum dots by combining low-temperature deposition with superior crystalline quality in the background of an amorphous hydrogenated silicon nitride matrix. Here, we make quantum dot thin films in a reactive mixture of ammonia/silane/hydrogen utilizing dual-frequency capacitively coupled plasmas with high atomic hydrogen and nitrogen radical densities. Systematic data analysis using different film and plasma characterization tools reveals that the quantum dots with different sizes exhibit size dependent film properties, which are sensitively dependent on plasma characteristics. These films exhibit intense photoluminescence in the visible range with violet to orange colors and with narrow to broad widths (∼0.3-0.9 eV). The observed luminescence behavior can come from the quantum confinement effect, quasi-direct band-to-band recombination, and variation of atomic hydrogen and nitrogen radicals in the film growth network. The high luminescence yields in the visible range of the spectrum and size-tunable low-temperature synthesis with plasma and radical control make these quantum dot films good candidates for light emitting applications.

  12. Plasma rest frame frequencies and polarizations of the low-frequency upstream waves - ISEE 1 and 2 observations

    NASA Technical Reports Server (NTRS)

    Hoppe, M. M.; Russell, C. T.

    1983-01-01

    The plasma rest frame frequencies and polarizations of the large amplitude low frequency (0.03 Hz) upstream waves are investigated using magnetic field data from the dual ISEE 1 and 2 spacecraft. The monochromatic sinusoidal waves associated with intermediate ion fluxes are propagating in both the Alfven and magnetosonic modes, in both cases with typical frequencies approximately 0.1 times the local proton gyrofrequency and wavelengths of approximately 1 R(E). It is shown that the generation of the magnetosonic mode can be explained by the cyclotron resonance mechanism driven by narrow reflected ion beams, but the concurrent observation of Alfven mode waves appears to require wave generation by the more isotropic diffuse ion distributions as well.

  13. Sterilization characteristics of dental instruments using oxygen plasma produced by narrow gap RF discharge

    NASA Astrophysics Data System (ADS)

    Sakai, Yasuhiro; Liu, Zhen; Goto, Masaaki; Hayashi, Nobuya

    2016-07-01

    Sterilization characteristics and material compatibility of low-pressure RF oxygen plasma sterilization method for dental instruments are investigated. Regarding the characteristics of the plasma sterilizer for dental instruments, it is small and can rapidly sterilize owing to a narrow gap discharge. Sterilization of vial-type biological indicators is achieved for the shortest treatment period of 40 min at an RF power of 80 W at a temperature of 70 °C. At a temperature lower than 60 °C, a sterilization period of 90 min is required using a water-cooled electrode. No surface modifications of dental instruments such as chemical composition and deterioration of fine crystals of a diamond bar were observed under a scanning electron microscope.

  14. Anchoring gold nanoparticles onto a mica surface by oxygen plasma ashing for sequential nanocomponent assembly

    NASA Astrophysics Data System (ADS)

    Takagi, Akihiko; Ojima, Kaoru; Mikamo, Eriko; Matsumoto, Takuya; Kawai, Tomoji

    2007-01-01

    Water-soluble gold nanoparticles were immobilized in both polar (water) and nonpolar (chloroform) liquids on hydrophilic mica surface by oxygen plasma ashing. It is then demonstrated that a DNA with a thiol at an extremity is attached to the immobilized nanoparticles due to the gold-thiol coupling and stretched in the flow direction of the following water rinse. This technique allows a sequential integration of nanoparticles and molecules for various solutions, since the nanoparticles remain on a solid surface rather than dissolve into the solution.

  15. Plasma uniformity and phase-controlled etching in a very high frequency capacitive discharge

    SciTech Connect

    Sung, Dougyong; Woo, Jehun; Lim, Kyungchun; Kim, Kyungsun; Volynets, Vladimir; Kim, Gon-Ho

    2009-07-15

    The influence of controlled phase shift between very high frequency (100 MHz) voltages applied to the powered electrodes on the plasma uniformity and etch rate was studied in a capacitive triode-type reactor. Radial profiles of plasma optical emission were measured as a function of the phase shift in process (C{sub 4}F{sub 8}/O{sub 2}/Ar) plasma with the low frequency bias power both turned off and on. Radial profiles of KrF photoresist etch rate over a 300 mm wafer were obtained in the same conditions (with the bias power turned on). Besides, plasma density at the wafer center and edge was measured versus the phase shift in pure Ar plasma. It occurred that all measured characteristics strongly depend on the phase shift and correlate with each other. It has been shown that the phase-shift control can considerably improve both the plasma and etch-rate uniformity in very high-frequency capacitive reactors.

  16. 3D-Spirals Emerging from Plasma Disk Structures and High Frequency QPOs*

    NASA Astrophysics Data System (ADS)

    Rebusco, P.; Coppi, B.; Bursa, M.

    2009-11-01

    An interpretation based on a novel kind of plasma modes[1] emerging from axisymmetric disks is proposed for High-Frequency Quasi-Periodic Oscillations (HFQPOs) in low mass X-ray binaries supporting the fact that QPOs can be a probe of strong field gravity. Tri-dimensional, tightly wound spirals are considered that co-rotate with the magnetized plasma disk structure surrounding a black hole at a radial distance that is related to the radius of the marginally stable orbit. These modes can be excited under the combined effects of the differential rotation and the vertical gradients of the plasma density and temperature. The spirals are localized over relatively narrow radial widths and have frequencies that are multiples of the plasma rotation frequency. The high toroidal number mφ modes are considered to decay into mφ=2 and mφ=3 modes, explaining the observed twin peak QPOs spectra with the 3:2 ratio. The modulation of the observed radiation associated with general relativistic effects is analyzed, considering different emission processes. These are connected to strong variations of the plasma collisionality parameters corresponding to a local rarefaction and heating, or to a local increase of plasma density and cooling due to the considered spirals. *Sponsored in part by the U.S. DOE and the Pappalardo Fellowship program. 1. B. Coppi, MIT-LNS Report 08/08, to be published in A&A (2009).

  17. Analysis by oxygen atom number density measurement of high-speed hydrophilic treatment of polyimide using atmospheric pressure microwave plasma

    SciTech Connect

    Ono, S.

    2015-03-30

    This paper describes the fundamental experimental data of the plasma surface modification of the polyimide using atmospheric pressure microwave plasma source. The experimental results were discussed from the point of view of the radical’s behavior, which significantly affects the modification mechanism. The purpose of the study is to examine how the value of the oxygen atom density will affect the hydrophilic treatment in the upstream region of the plasma where gas temperature is very high. The surface modification experiments were performed by setting the polyimide film sample in the downstream region of the plasma. The degree of the modification was measured by a water contact angle measurement. The water contact angle decreased less than 30 degrees within 1 second treatment time in the upstream region. Very high speed modification was observed. The reason of this high speed modification seems that the high density radical which contributes the surface modification exist in the upstream region of the plasma. This tendency is supposed to the measured relatively high electron density (~10{sup 15}cm{sup −3}) at the center of the plasma. We used the electric heating catalytic probe method for oxygen radical measurement. An absolute value of oxygen radical density was determined by catalytic probe measurement and the results show that ~10{sup 15}cm{sup −3} of the oxygen radical density in the upstream region and decreases toward downstream region. The experimental results of the relation of the oxygen radical density and hydrophilic modification of polyimide was discussed.

  18. Cyclotron mode frequencies and resonant absorption in multi-species ion plasmas

    SciTech Connect

    Affolter, M.; Anderegg, F.; Dubin, D. H. E.; Driscoll, C. F.

    2015-05-15

    Cyclotron mode frequencies are studied on trapped rigid-rotor multi-species ion plasmas. Collective effects and radial electric fields shift the mode frequencies away from the “bare” cyclotron frequencies 2πF{sub c}{sup (s)}≡(q{sub s}B/M{sub s}c) for each species s. These frequency shifts are measured on the distinct cyclotron modes (m=0,1, and 2) with cos(mθ) azimuthal dependence. We find that for radially uniform plasmas the frequency shifts corroborate a simple theory expression, in which collective effects enter only through the E × B rotation frequency f{sub E} and the species fraction δ{sub s}. The m = 1 center-of-mass mode is in agreement with a simple “clump” model. Additionally, ultra-cold ion plasmas exhibit centrifugal separation by mass, and additional frequency shifts are observed, in agreement with a more general theory.

  19. Tensile strength of oxygen plasma-created surface layer of PDMS

    NASA Astrophysics Data System (ADS)

    Ohishi, Taiki; Noda, Haruka; Matsui, Tsubasa S.; Jile, Huge; Deguchi, Shinji

    2017-01-01

    Polydimethylsiloxane (PDMS) is a commonly used silicone elastomer with broad applications. Particularly for bioengineering use, PDMS is treated with oxygen plasma with which its surface is oxidized to allow positive interaction with water and live cells. In exchange for the acquisition of hydrophilicity, the oxidized PDMS becomes mechanically brittle so that resulting formation of cracks affects the system in various ways. However, tensile strength (TS), which is an inherent capacity of a material to withstand tensile loads before breaking and is thus a key parameter limiting the use of the material, remains unclear regarding oxidized PDMS. Here we determine the TS of oxide layers created on the surface of PDMS based on micro-stretch experiments using a custom-made device. We show that the surface layer displays cracks upon tensile loading of small strains of within 10% to have a TS of ~10-100 kPa, which is approximately two orders of magnitude lower than that of unmodified PDMS. We further show that the TS sharply decreases with oxidation duration to become highly brittle, while the thickness of the resulting oxide layer finally reaches a plateau even with prolonged plasma treatment. Consequently, we suggest that gradual surface modification of PDMS takes place only within a finite region even with prolonged plasma treatment, as distinct from previously held assumptions. These quantitative data provide critical design information for the oxide layer of plasma-hydrophilized PDMS.

  20. Production characteristics of reactive oxygen/nitrogen species in water using atmospheric pressure discharge plasmas

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazuhiro; Satoh, Kohki; Itoh, Hidenori; Kawaguchi, Hideki; Timoshkin, Igor; Given, Martin; MacGregor, Scott

    2016-07-01

    A pulsed discharge, a DC corona discharge, and a plasma jet are separately generated above a water surface, and reactive oxygen species and reactive nitrogen species (ROS/RNS) in the water are investigated. ROS/RNS in water after the sparging of the off-gas of a packed-bed dielectric barrier discharge (PB-DBD) are also investigated. H2O2, NO2 -, and NO3 - are detected after plasma exposure and only NO3 - after off-gas sparging. Short-lifetime species in plasma are found to play an important role in H2O2 and NO2 - production and long-lifetime species in NO3 - production. NO x may inhibit H2O2 production through OH consumption to produce HNO2 and HNO3. O3 does not contribute to ROS/RNS production. The pulsed plasma exposure is found to be effective for the production of H2O2 and NO2 -, and the off-gas sparging of the PB-DBD for the production of NO3 -.

  1. Discontinuous model with semi analytical sheath interface for radio frequency plasma

    NASA Astrophysics Data System (ADS)

    Miyashita, Masaru

    2016-09-01

    Sumitomo Heavy Industries, Ltd. provide many products utilizing plasma. In this study, we focus on the Radio Frequency (RF) plasma source by interior antenna. The plasma source is expected to be high density and low metal contamination. However, the sputtering the antenna cover by high energy ion from sheath voltage still have been problematic. We have developed the new model which can calculate sheath voltage wave form in the RF plasma source for realistic calculation time. This model is discontinuous that electronic fluid equation in plasma connect to usual passion equation in antenna cover and chamber with semi analytical sheath interface. We estimate the sputtering distribution based on calculated sheath voltage waveform by this model, sputtering yield and ion energy distribution function (IEDF) model. The estimated sputtering distribution reproduce the tendency of experimental results.

  2. Degradation of methylene blue by radio frequency plasmas in water under ultraviolet irradiation.

    PubMed

    Maehara, Tsunehiro; Nishiyama, Kyohei; Onishi, Shingo; Mukasa, Shinobu; Toyota, Hiromichi; Kuramoto, Makoto; Nomura, Shinfuku; Kawashima, Ayato

    2010-02-15

    The degradation of methylene blue by radio frequency (RF) plasmas in water under ultraviolet (UV) irradiation was studied experimentally. When the methylene blue solution was exposed to RF plasma, UV irradiation from a mercury vapor lamp enhanced degradation significantly. A lamp without power supply also enhanced degradation since weak UV light was emitted weakly from the lamp due to the excitation of mercury vapor by stray RF power. Such an enhancement is explained by the fact that after hydrogen peroxide is produced via the recombination process of OH radicals around the plasma, OH radicals reproduced from hydrogen peroxide via the photolysis process degrade methylene blue.

  3. Strong Field-Induced Frequency Conversion of Laser Radiation in Plasma Plumes: Recent Achievements

    PubMed Central

    Ganeev, R. A.

    2013-01-01

    New findings in plasma harmonics studies using strong laser fields are reviewed. We discuss recent achievements in the growth of the efficiency of coherent extreme ultraviolet (XUV) radiation sources based on frequency conversion of the ultrashort pulses in the laser-produced plasmas, which allowed for the spectral and structural studies of matter through the high-order harmonic generation (HHG) spectroscopy. These studies showed that plasma HHG can open new opportunities in many unexpected areas of laser-matter interaction. Besides being considered as an alternative method for generation of coherent XUV radiation, it can be used as a powerful tool for various spectroscopic and analytical applications. PMID:23864818

  4. Broadband radio frequency plasma generation in a Penning-Malmberg trap

    NASA Astrophysics Data System (ADS)

    Paroli, B.; De Luca, F.; Maero, G.; Pozzoli, R.; Romé, M.

    2010-08-01

    Plasma generation is observed in a cylindrical Penning-Malmberg trap in the ultra-high vacuum pressure regime for a large bandwidth of low-power radio frequency (RF) excitations. The process of plasma formation is investigated by measuring the density profiles and a simplified model is developed to characterize the electron heating mechanism. The total charge confined at equilibrium is systematically studied for RF drives in the 0.1-20 MHz range and with different geometrical configurations. With electron densities of some 106 cm-3 at least, the scheme represents an alternative source of non-neutral plasmas for Penning-Malmberg traps.

  5. Tissue blood flow and oxygen consumption measured with near-infrared frequency-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Paunescu, Lelia Adelina

    2001-12-01

    For decades, researchers have contributed with new ways of applying physics' principles to medicine. Moreover, researchers were involved in developing new, non-invasive instrumentation for medical applications. Recently, application of optical techniques in biology and medicine became an important field. Researchers found a non- invasive approach of using visible and near-infrared light as a probe for tissue investigation. Optical methods can contribute to medicine by offering the possibility of rapid, low-resolution, functional images and real-time devices. Near-infrared spectroscopy (NIRS) is a useful technique for the investigation of biological tissues because of the relatively low absorption of water and high absorption of oxy- and deoxy-hemoglobin in the near- infrared region of 750-900 nm. Due to these properties, the near-infrared light can penetrate biological tissues in the range of 0.5-2 cm, offering investigation possibility of deep tissues and differentiate among healthy and diseased tissues. This work represents the initial steps towards understanding and improving of the promising near- infrared frequency-domain technique. This instrument has a very important advantage: it can be used non-invasively to investigate many parts of the human body, including the brain. My research consists primarily of in vivo measurements of optical parameters such as absorption and reduced scattering coefficients and consequently, blood parameters such as oxy, deoxy, and total hemoglobin concentrations, tissue oxygen saturation, blood flow and oxygen consumption of skeletal muscle of healthy and diseased subjects. This research gives a solid background towards a ready- to-use instrument that can continuously, in real-time, measure blood parameters and especially blood oxygenation. This is a very important information in emergency medicine, for persons under intensive care, or undergoing surgery, organ transplant or other interventions.

  6. High Frequency Plasma Waves Associated With Solar Wind Reconnection Exhausts: WIND/WAVES Observations

    NASA Astrophysics Data System (ADS)

    Huttunen, K. E.; Bale, S. D.; Phan, T. D.; Davis, M.; Gosling, J. T.

    2006-12-01

    Observations of strong plasma wave activity near reconnection X-line regions in THE laboratory and in the Earth's magnetosphere have suggested that plasma waves may play AN important role in the reconnection process by providing anomalous resistivity through wave-particle interactions and by accelerating electrons. Recent observations of quasi-steady magnetic reconnection in the solar wind introduces an important new environment to study the role of plasma waves in a collisionless plasma associated with the reconnection process. We have used observations by the WIND spacecraft to study high frequency plasma waves associated with 28 solar wind reconnection exhausts. The TNR (Thermal Noise Receiver) experiment included in the WAVES instrument on WIND measures electric spectral density from 4 to 256 kHz and the TDS (Time Domain Sampler) experiment also included in WAVES samples electric field waveforms at rates up to 120,000 samples/s. A large fraction (79%) of the investigated events showed significant enhancements in the wave power around ~ 4 kHz, while only about one third (39%) of the exhausts were associated with intensifications around THE local electron plasma frequency (few tens of kHz). TDS waveform samples revealed three different wave modes: electron solitary waves, ion acoustic waves and Langmuir waves. The intense plasma waves were most frequently observed close to the X-line and near the exhaust boundaries, although wave emissions were commonly observed elsewhere within the exhausts as well

  7. The different effects of oxygen and air DBD plasma byproducts on the degradation of methyl violet 5BN.

    PubMed

    Chen, Guangliang; Zhou, Mingyan; Chen, Shihua; Chen, Wenxing

    2009-12-30

    Through a novel design of the dielectric barrier discharge (DBD) plasma plume used in fabric-fiber surface modification, its discharge byproducts mainly including downstream gases and ultraviolet light were used to treat the dye solution. The different influence of oxygen and air DBD plasmas on the degradation of methyl violet 5BN (MV-5BN), which is widely used in textile industry, was investigated in this paper. The results showed that the cooperation between ultraviolet light and active species generated by the DBD plasma can decolorize MV-5BN effectively, and the chromophore peaks attributed to the -NN- bonds in MV-5BN molecule disappeared entirely when the azo dye solutions were treated for 25 min by the air and oxygen DBD plasmas. The degradation reaction followed an exponential kinetics over time, and the peak of aromatic derivatives at 209 nm in UV-vis spectra increased nearly 2.7 times when the dye solution was treated for 30 min by air DBD plasma. However, the oxygen DBD plasma could deplete the aromatic derivatives entirely. It is found that the formation of O(3) and NO(x) in the downstream gases of air and oxygen plasmas may be responsible for the different effects on the azo dye degradation.

  8. Effect of oxygen atoms dissociated by non-equilibrium plasma on flame of methane oxygen and argon pre-mixture gas

    NASA Astrophysics Data System (ADS)

    Akashi, Haruaki; Yoshinaga, Tomokazu; Sasaki, Koichi

    2014-10-01

    For more efficient way of combustion, plasma-assisted combustion has been investigated by many researchers. But it is very difficult to clarify the effect of plasma even on the flame of methane. Because there are many complex chemical reactions in combustion system. Sasaki et al. has reported that the flame length of methane and air premixed burner shortened by irradiating microwave power. They also measured emission from Second Positive Band System of nitrogen during the irradiation. The emission indicates existence of high energy electrons which are accelerated by the microwave. The high energy electrons also dissociate oxygen molecules easily and oxygen atom would have some effects on the flame. But the dissociation ratio of oxygen molecules by the non-equilibrium plasma is significantly low, compared to that in the combustion reaction. To clarify the effect of dissociated oxygen atoms on the flame, dependence of dissociation ratio of oxygen on the flame has been examined using CHEMKIN. It is found that in the case of low dissociation ratio of 10-6, the ignition of the flame becomes slightly earlier. It is also found that in the case of high dissociation ratio of 10-3, the ignition time becomes significantly earlier by almost half. This work was supported by KAKENHI (22340170).

  9. Experimental investigations of the formation of a plasma mirror for high-frequency microwave beam steering

    NASA Astrophysics Data System (ADS)

    Meger, R. A.; Mathew, J.; Gregor, J. A.; Pechacek, R. E.; Fernsler, R. F.; Manheimer, W.; Robson, A. E.

    1995-06-01

    The Naval Research Laboratory (NRL) has been studying the use of a magnetically confined plasma sheet as a reflector for high-frequency (X-band) microwaves for broadband radar applications [IEEE Trans. Plasma Sci. PS-19, 1228 (1991)]. A planar sheet plasma (50 cm×60 cm×1 cm) is produced using a 2-10 kV fast rise time square wave voltage source and a linear hollow cathode. Reproducible plasma distributions with density ≥1.2×1012 cm-3 have been formed in a low-pressure (100-500 mTorr of air) chamber located inside of a 100-300 G uniform magnetic field. One to ten pulse bursts of 20-1000 μs duration plasma sheets have been produced with pulse repetition frequencies of up to 10 kHz. Turn on and off times of the plasma are less than 10 μs each. The far-field antenna pattern of microwaves reflected off the plasma sheet is similar to that from a metal plate at the same location [IEEE Trans. Plasma Sci PS-20, 1036 (1992)]. Interferometer measurements show the critical surface to remain nearly stationary during the current pulse. Plasma density measurements and optical emissions indicate that the plasma is produced by a flux of energetic electrons formed near the hollow cathode. The sheet appears to be stable to driver voltage and current fluctuations (NRL Memorandum Report No. 7461, 28 March 1994, NTIS Document No. AD-A278758).

  10. Multiple frequency capacitive plasmas as a tool to optimize PVD processes

    NASA Astrophysics Data System (ADS)

    Bienholz, Stefan; Semmler, Egmont; Awakowicz, Peter

    2011-10-01

    Capacitively coupled plasmas are widely used in PVD processes over several years. Nowadays mainly DC-Magnetron sputter coaters are commonly used, which do not allow a separate control of ion flux and ion energy distribution at the target. A possibility to overcome this constriction consists of exciting the plasma at two different radio frequencies simultaneously. In this contribution we discuss the possibility of tuning electrical discharge quantities such as target voltage waveform and self bias voltage by using multiple excitation frequencies. The influence of the relative phase between one frequency and its second harmonic on these quantities is also investigated. The experiments show, that capacitively coupled multiple frequency discharges are a promising complement to existing PVD processes. The authors would like to acknowledge the funding provided by the ``Deutsche Forschungsgemeinschaft'' within the frame of the SFB-TR 87 and the ``Ruhr University Bochum Research School.''

  11. A new method for determining the plasma electron density using optical frequency comb interferometer

    SciTech Connect

    Arakawa, Hiroyuki Tojo, Hiroshi; Sasao, Hajime; Kawano, Yasunori; Itami, Kiyoshi

    2014-04-15

    A new method of plasma electron density measurement using interferometric phases (fractional fringes) of an optical frequency comb interferometer is proposed. Using the characteristics of the optical frequency comb laser, high density measurement can be achieved without fringe counting errors. Simulations show that the short wavelength and wide wavelength range of the laser source and low noise in interferometric phases measurements are effective to reduce ambiguity of measured density.

  12. Room temperature radio-frequency plasma-enhanced pulsed laser deposition of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Huang, S.-H.; Chou, Y.-C.; Chou, C.-M.; Hsiao, V. K. S.

    2013-02-01

    In this study, we compared the crystalline structures, optical properties, and surface morphologies of ZnO thin films deposited on silicon and glass substrates by conventional pulsed laser deposition (PLD) and radio-frequency (RF) plasma-enhanced PLD (RF-PEPLD). The depositions were performed at room temperature under 30-100 mTorr pressure conditions. The RF-PEPLD process was found to have deposited a ZnO structure with preferred (0 0 2) c-axis orientation at a higher deposition rate; however, the RF-PEPLD process generated more defects in the thin films. The application of oxygen pressure to the RF-PEPLD process reduced defects effectively and also increased the deposition rate.

  13. Modeling of plasma transport and negative ion extraction in a magnetized radio-frequency plasma source

    NASA Astrophysics Data System (ADS)

    Fubiani, G.; Garrigues, L.; Hagelaar, G.; Kohen, N.; Boeuf, J. P.

    2017-01-01

    Negative ion sources for fusion are high densities plasma sources in large discharge volumes. There are many challenges in the modeling of these sources, due to numerical constraints associated with the high plasma density, to the coupling between plasma and neutral transport and chemistry, the presence of a magnetic filter, and the extraction of negative ions. In this paper we present recent results concerning these different aspects. Emphasis is put on the modeling approach and on the methods and approximations. The models are not fully predictive and not complete as would be engineering codes but they are used to identify the basic principles and to better understand the physics of the negative ion sources.

  14. Generation of Alfven waves by high power pulse at the electron plasma frequency

    NASA Astrophysics Data System (ADS)

    van Compernolle, Bart Gilbert

    The physics of the interaction between plasmas and high power waves with frequencies in the electron plasma frequency range is of importance in many areas of space and plasma physics. A great deal of laboratory research has been done on the interaction of microwaves in a density gradient when o = ope in unmagnetized plasmas. [SWK74, WS78, KSW74]. Extensive studies of HF-ionospheric modifications have been performed [Fej79] as evidenced by experiments at Arecibo [HMD92, BHK86, CDF92, FGI85], at the HAARP facility [RKK98] in Alaska, at the EISCAT observatory in Norway [IHR99], and at SURA in Russia [FKS99]. This dissertation focusses on the interaction with a fully magnetized plasma, capable of supporting Alfven waves. The experiment is performed in the upgraded LArge Plasma Device (LAPD) at UCLA [GPL91] (Helium, n = 1012 cm-3, B = 1 kG - 2.5 kG). A number of experiments have been done at LAPD using antennas, skin depth scale currents and laser produced plasmas to generate Alfven waves [LGM99, GVL97a, GVL97b, VGV01]. In this work a high power pulse 6th, frequency in the electron plasma frequency range is launched into the radial density gradient, perpendicular to the background magnetic field. The microwave pulses last on the order of one ion gyro period and has a maximum power of |E|2/ nT ≃ .5 in the afterglow. The absorption of these waves leads to a pulse of field aligned suprathermal electrons. This electron current pulse then launches with Alfven wave with o ≤ o ci. The experiment was performed bath in ordinary node (O-mode) and extraordinary (X-mode), for different background magnetic fields B0, different temperatures (afterglow vs discharge) and different power levels of the incoming microwaves. It was found that the Alfven wave generation can be explained by Cherenkov radiation of Alfven waves by the suprathermal electron pulse. Theoretical solutions for the perturbed magnetic field due to a pulse of field aligned electrons were obtained, and shown to be

  15. A Hilbert-Vlasov code for the study of high-frequency plasma beatwave accelerator

    SciTech Connect

    Ghizzo, A.; Bertrand, P.; Begue, M.L.; Johnston, T.W.; Shoucri, M.

    1996-04-01

    High-frequency beatwave simulations relevant to the University of California at Los Angeles (UCLA) experiment with relativistic eulerian hybrid Vlasov code are presented. These Hilbert-Vlasov simulations revealed a rich variety of phenomena associated with the fast particle dynamics induced by beatwave experiment for a high ratio of driver frequency to plasma frequency {omega}{sub pump}/{omega}{sub pump} {approx} 33. The present model allows one to extend detailed modeling to frequency ratios greater than the current practical maximum of 10 or so, for Vlasov or particle-in-cell (PIC) codes, by replacing the Maxwell equations by mode equations for the electromagnetic Vlasov code. Numerical results, including beat frequency chirping (i.e., pump frequency linearly decreasing with time), show that the amplitude limit due to relativistic detuning can be enhanced with accelerated particles up to the ultrarelativistic energies with a high-acceleration gradient of more than 25 GeV/m.

  16. Impact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids

    SciTech Connect

    Jablonowski, H.; Hammer, M. U.; Reuter, S.; Bussiahn, R.; Weltmann, K.-D.; Woedtke, Th. von

    2015-12-15

    Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100–400 nm) and, in particular, vacuum ultraviolet (VUV, 10–200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH{sub 2}O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stable reactive oxygen species, hydrogen peroxide (H{sub 2}O{sub 2}) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O{sub 2}{sup •−}) and hydroxyl radicals ({sup •}OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.

  17. Impact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids

    NASA Astrophysics Data System (ADS)

    Jablonowski, H.; Bussiahn, R.; Hammer, M. U.; Weltmann, K.-D.; von Woedtke, Th.; Reuter, S.

    2015-12-01

    Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100-400 nm) and, in particular, vacuum ultraviolet (VUV, 10-200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH2O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stable reactive oxygen species, hydrogen peroxide (H2O2) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O2•-) and hydroxyl radicals (•OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.

  18. Blood oxygenation changes resulting from trains of low frequency transcranial magnetic stimulation.

    PubMed

    Thomson, Richard H; Maller, Jerome J; Daskalakis, Zafiris J; Fitzgerald, Paul B

    2012-04-01

    The evoked responses to transcranial magnetic stimulation (TMS) have been previously demonstrated to be on average greater at the beginning of a session; however the physiological reason for this remains uncertain. In order to investigate a possible hemodynamic mechanism for this phenomenon, changes in oxy-hemoglobin (HbO) following trains of single pulse TMS was investigated using near infra-red spectroscopy (NIRS). TMS was delivered in trains of two and four pulses to left pre-frontal cortex (PFC) at a typical intensity and frequency (.2 Hz) used in neuroscience research. Both trains resulted in significant drops of HbO that remained after the cessation of TMS. The changes observed imply that arterial supply drops following suprathreshold TMS and oxygen consumption outstrips supply, resulting in a net drop of HbO. This study provides evidence that at typical TMS delivery frequencies, local HbO levels remain at a sustained lower level than at the beginning of the session, potentially explaining changes in sensitivity to stimulation with repeated TMS pulses.

  19. In vivo stimulation of bone formation by aluminum and oxygen plasma surface-modified magnesium implants.

    PubMed

    Wong, Hoi Man; Zhao, Ying; Tam, Vivian; Wu, Shuilin; Chu, Paul K; Zheng, Yufeng; To, Michael Kai Tsun; Leung, Frankie K L; Luk, Keith D K; Cheung, Kenneth M C; Yeung, Kelvin W K

    2013-12-01

    A newly developed magnesium implant is used to stimulate bone formation in vivo. The magnesium implant after undergoing dual aluminum and oxygen plasma implantation is able to suppress rapid corrosion, leaching of magnesium ions, as well as hydrogen gas release from the biodegradable alloy in simulated body fluid (SBF). No released aluminum is detected from the SBF extract and enhanced corrosion resistance properties are confirmed by electrochemical tests. In vitro studies reveal enhanced growth of GFP mouse osteoblasts on the aluminum oxide coated sample, but not on the untreated sample. In addition to that a small amount (50 ppm) of magnesium ions can enhance osteogenic differentiation as reported previously, our present data show a low concentration of hydrogen can give rise to the same effect. To compare the bone volume change between the plasma-treated magnesium implant and untreated control, micro-computed tomography is performed and the plasma-treated implant is found to induce significant new bone formation adjacent to the implant from day 1 until the end of the animal study. On the contrary, bone loss is observed during the first week post-operation from the untreated magnesium sample. Owing to the protection offered by the Al2O3 layer, the plasma-treated implant degrades more slowly and the small amount of released magnesium ions stimulate new bone formation locally as revealed by histological analyses. Scanning electron microscopy discloses that the Al2O3 layer at the bone-implant interface is still present two months after implantation. In addition, no inflammation or tissue necrosis is observed from both treated and untreated implants. These promising results suggest that the plasma-treated magnesium implant can stimulate bone formation in vivo in a minimal invasive way and without causing post-operative complications.

  20. Titanium dioxide nanoparticles increase plasma glucose via reactive oxygen species-induced insulin resistance in mice.

    PubMed

    Hu, Hailong; Guo, Qian; Wang, Changlin; Ma, Xiao; He, Hongjuan; Oh, Yuri; Feng, Yujie; Wu, Qiong; Gu, Ning

    2015-10-01

    There have been few reports about the possible toxic effects of titanium dioxide (TiO2 ) nanoparticles on the endocrine system. We explored the endocrine effects of oral administration to mice of anatase TiO2 nanoparticles (0, 64 and 320 mg kg(-1) body weight per day to control, low-dose and high-dose groups, respectively, 7 days per week for 14 weeks). TiO2 nanoparticles were characterized by scanning and transmission electron microscopy (TEM) and dynamic light scattering (DLS), and their physiological distribution was investigated by inductively coupled plasma. Biochemical analyzes included plasma glucose, insulin, heart blood triglycerides (TG), free fatty acid (FFA), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), total cholesterol (TC), tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6 and reactive oxygen species (ROS)-related markers (total SOD, GSH and MDA). Phosphorylation of IRS1, Akt, JNK1, and p38 MAPK were analyzed by western blotting. Increased titanium levels were found in the liver, spleen, small intestine, kidney and pancreas. Biochemical analyzes showed that plasma glucose significantly increased whereas there was no difference in plasma insulin secretion. Increased ROS levels were found in serum and the liver, as evidenced by reduced total SOD activity and GSH level and increased MDA content. Western blotting showed that oral administration of TiO2 nanoparticles induced insulin resistance (IR) in mouse liver, shown by increased phosphorylation of IRS1 (Ser307) and reduced phosphorylation of Akt (Ser473). The pathway by which TiO2 nanoparticles increase ROS-induced IR were included in the inflammatory response and phosphokinase, as shown by increased serum levels of TNF-α and IL-6 and increased phosphorylation of JNK1 and p38 MAPK in liver. These results show that oral administration of TiO2 nanoparticles increases ROS, resulting in IR and increasing plasma glucose in mice.

  1. Preface to Special Topic: Advances in Radio Frequency Physics in Fusion Plasmas

    SciTech Connect

    Tuccillo, Angelo A.; Ceccuzzi, Silvio; Phillips, Cynthia K.

    2014-06-15

    It has long been recognized that auxiliary plasma heating will be required to achieve the high temperature, high density conditions within a magnetically confined plasma in which a fusion “burn” may be sustained by copious fusion reactions. Consequently, the application of radio and microwave frequency electromagnetic waves to magnetically confined plasma, commonly referred to as RF, has been a major part of the program almost since its inception in the 1950s. These RF waves provide heating, current drive, plasma profile control, and Magnetohydrodynamics (MHD) stabilization. Fusion experiments employ electromagnetic radiation in a wide range of frequencies, from tens of MHz to hundreds of GHz. The fusion devices containing the plasma are typically tori, axisymmetric or non, in which the equilibrium magnetic fields are composed of a strong toroidal magnetic field generated by external coils, and a poloidal field created, at least in the symmetric configurations, by currents flowing in the plasma. The waves are excited in the peripheral regions of the plasma, by specially designed launching structures, and subsequently propagate into the core regions, where resonant wave-plasma interactions produce localized heating or other modification of the local equilibrium profiles. Experimental studies coupled with the development of theoretical models and advanced simulation codes over the past 40+ years have led to an unprecedented understanding of the physics of RF heating and current drive in the core of magnetic fusion devices. Nevertheless, there are serious gaps in our knowledge base that continue to have a negative impact on the success of ongoing experiments and that must be resolved as the program progresses to the next generation devices and ultimately to “demo” and “fusion power plant.” A serious gap, at least in the ion cyclotron (IC) range of frequencies and partially in the lower hybrid frequency ranges, is the difficulty in coupling large amount of

  2. 3D-Spirals Emerging from Plasma Disks and High Frequency QPOs*

    NASA Astrophysics Data System (ADS)

    Rebusco, P.; Coppi, B.; Bursa, M.

    2009-05-01

    An interpretation based on a novel kind of plasma modes emerging from axisymmetric disks is proposed for High-Frequency Quasi-Periodic Oscillations (HFQPOs) in low mass X-ray binaries as QPOs can be a probe of strong field gravity. Tri-dimensional, tightly wound spirals are considered that co-rotate with the magnetized plasma disk surrounding a black hole in the vicinity of the marginally stable orbit. These modes can be excited by the combined effects of the differential rotation and the vertical gradients of the plasma density and temperature. The spirals are localized over relatively narrow radial widths and have frequencies that are multiples of the plasma rotation frequency. The high toroidal number mφ modes are considered to decay into mφ=2 and mφ=3 modes, explaining the observed twin peak QPOs spectra with the 3:2 ratio. The modulation of the observed radiation associated with general relativistic effects is analyzed, considering different emission processes. These are connected to strong variations of the runaway electric field corresponding to a local rarefaction and heating, or to a local increase of plasma density and cooling due to the considered spirals. *Sponsored in part by the U.S. DOE and the Pappalardo Fellowship program. B. Coppi, MIT/LNS Report 08/08, submitted to Astronomy and Astrophysics (2008).

  3. Excitation of Josephson Plasma Resonance in BISMUTH(2) STRONTIUM(2) Calcium COPPER(2) OXYGEN(8+DELTA)

    NASA Astrophysics Data System (ADS)

    Tsui, Ophelia Kwan Chui

    A novel magnetic resonance is observed in Bi_2Sr_2CaCu_2O_{8+ delta} single crystals exposed to microwave radiation (26 to 95 GHz) in the presence of a magnetic field. The resonance exhibits unconventional field and temperature dependence. At a fixed temperature below the melting transition of the vortex solid, T_ {m}(B), the resonance frequency decreases with the applied field and displays a power-law dependence, viz. omega~ B^{-mu }. The exponent was found to be 0.8 within 10% across all samples and temperatures studied. However, when the temperature is increased above T_ {m}(B), mu becomes sample dependent and is equal to 0.64 and 1.08 for the two samples studied. At fixed microwave frequencies, the resonance field, B_0 increases exponentially with temperature to a maximum at T_{m }(B) and decreases slowly with temperature above. We attribute the resonance to Josephson plasma oscillations excited along the sample c-axis. The model explains many features of the experiment. Recently, Bulaevskii et al. proposed an explanation for the field dependence of the Josephson plasma frequency. By assuming that disorder in vortex pancakes is caused by strong pinning at low temperatures, the authors obtained the power-law dependence of omega on B, which agrees with the experiment. Rotating the microwave E-field, { bf E}_{rf} relatively to the sample, we find maximum resonance absorption when {bf E}_{rf} has the maximum projection along the sample c-axis, and minimum when there is none. This identification of {bf E}_{rf} parallel to the sample c-axis as the one responsible for the resonance, supports the Josephson plasma hypothesis. The strongest evidence for the Josephson plasma model is obtained by tilting the magnetic field close to alignment with the ab-plane of the crystal. In that case, an unusual re-entrant cusp in B_0 is observed when the tilt angle is in the range -5.5^circ to 5.5^circ. This is consistent with Bulaevskii et al.'s calculation. They propose that pancake

  4. Microwave-Plasma-Coupled Re-Ignition of Methane-and-Oxygen Mixture Under Auto-Ignition Temperature

    DTIC Science & Technology

    2011-12-01

    plasma coupling (60-SCCM total flow rate at φ = 1.1). in situ fuel reforming (to hydrogen and carbon monoxide), as well as the temperature increase...Adamovich, “Non- thermal ignition of premixed hydrocarbon-air flows by nonequilibrium rf plasma ,” J. Propulsion Power, vol. 21, no. 4, pp. 583–590, Jul./Aug...IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 39, NO. 12, DECEMBER 2011 3307 Microwave- Plasma -Coupled Re-Ignition of Methane-and-Oxygen Mixture Under

  5. STUDENT AWARD FINALIST: Oxygen Pathways in Streamer Discharge for Transient Plasma Ignition

    NASA Astrophysics Data System (ADS)

    Pendleton, S. J.; Bowman, S.; Singleton, D.; Watrous, J.; Carter, C.; Lempert, W.; Gundersen, M. A.

    2011-10-01

    The use of streamers for the ignition of fuels, also known as transient plasma ignition (TPI), has been shown in a variety of engines to improve combustion through decreased ignition delay, increased lean burn capability and increased energy release relative to conventional spark ignition. The mechanisms behind these improvements, however, remain poorly understood. Temperature measurements by optical emission spectroscopy demonstrate that ignition by TPI is a nonthermal process, and thus is almost entirely dependent on the production and presence of electron impact-created active species in the discharge afterglow. Of particular interest are active oxygen species due to their relatively long lifetimes at high pressures and the pivotal role they play in combustion reactions. In order to elucidate the oxygen pathways, here we report the investigation of the temporal evolution of the populations of atomic oxygen and ozone by use of two-photon absorption laser induced fluorescence (TALIF) and UV absorption, respectively. Experimental results are presented and compared to kinetic modeling of the streamers. Future experiments are proposed to better understand the physics behind TPI. Supported by NSF, AFOSR, NumerEx-ONR, AFRL-WPAFB.

  6. Influence of wall plasma on microwave frequency and power in relativistic backward wave oscillator

    NASA Astrophysics Data System (ADS)

    Sun, Jun; Wu, Ping; Cao, Yibing; Teng, Yan; Zhang, Yuchuan; Chen, Changhua

    2015-07-01

    The RF breakdown of the slow wave structure (SWS), which will lead to the generation of the wall plasma, is an important cause for pulse shortening in relativistic backward wave oscillators. Although many researchers have performed profitable studies about this issue, the influence mechanism of this factor on the microwave generation still remains not-so-clear. This paper simplifies the wall plasma with an "effective" permittivity and researches its influence on the microwave frequency and power. The dispersion relation of the SWS demonstrates that the introduction of the wall plasma will move the dispersion curves upward to some extent, which is confirmed by particle-in-cell (PIC) simulations and experiments. The plasma density and volume mainly affect the dispersion relation at the upper and lower frequency limits of each mode, respectively. Meanwhile, PIC simulations show that even though no direct power absorption exists since the wall plasma is assumed to be static, the introduction of the wall plasma may also lead to the decrease in microwave power by changing the electrodynamic property of the SWS.

  7. Influence of wall plasma on microwave frequency and power in relativistic backward wave oscillator

    SciTech Connect

    Sun, Jun; Cao, Yibing; Teng, Yan; Zhang, Yuchuan; Chen, Changhua; Wu, Ping

    2015-07-15

    The RF breakdown of the slow wave structure (SWS), which will lead to the generation of the wall plasma, is an important cause for pulse shortening in relativistic backward wave oscillators. Although many researchers have performed profitable studies about this issue, the influence mechanism of this factor on the microwave generation still remains not-so-clear. This paper simplifies the wall plasma with an “effective” permittivity and researches its influence on the microwave frequency and power. The dispersion relation of the SWS demonstrates that the introduction of the wall plasma will move the dispersion curves upward to some extent, which is confirmed by particle-in-cell (PIC) simulations and experiments. The plasma density and volume mainly affect the dispersion relation at the upper and lower frequency limits of each mode, respectively. Meanwhile, PIC simulations show that even though no direct power absorption exists since the wall plasma is assumed to be static, the introduction of the wall plasma may also lead to the decrease in microwave power by changing the electrodynamic property of the SWS.

  8. Atomic oxygen recombination on the ODS PM 1000 at high temperature under air plasma

    NASA Astrophysics Data System (ADS)

    Balat-Pichelin, M.; Bêche, E.

    2010-06-01

    High temperature materials are necessary for the design of primary heat shields for future reusable space vehicles re-entering atmospheric planet at hypersonic velocity. During the re-entry phase on earth, one of the most important phenomena occurring on the heat shield is the recombination of atomic oxygen and this phenomenon is more or less catalyzed by the material of the heat shield. PM 1000 is planned to be use on the EXPERT capsule to study in real conditions its catalycity. Before the flight, it is necessary to perform measurements on ground test facility. Experimental data of the recombination coefficient of atomic oxygen under air plasma flow were obtained in the diffusion reactor MESOX on pre-oxidized PM 1000, for two total pressures 300 and 1000 Pa in the temperature range (850-1650 K) using actinometry and optical emission spectroscopy. In this investigation, the evolution of the recombination coefficient is dependent of temperature, pressure level and also of the chemical composition of the surface leading to one order of magnitude for a given temperature. The recombination coefficient is increasing with temperature and also dependent on the static pressure. The surface change due to the plasma exposure is inspected with SEM, XRD and XPS. As chromium oxide is the main part of the oxide layer formed during the oxidation in air plasma conditions, a sintered Cr 2O 3 sample was elaborated from powders to compare the data of the recombination coefficient obtained on PM 1000. Pre- and post-test analyses on the several materials were carried out using SEM, WDS, XRD and XPS.

  9. [Effect of radio frequency discharge plasma on surface properties and biocompatibility of polycaprolactone matrices].

    PubMed

    Bolbasov, E N; Antonova, L V; Matveeva, V G; Novikov, V A; Shesterikov, E V; Bogomolova, N L; Golovkin, A S; Tverdohlebov, S I; Barbarash, O L; Barbarash, L S

    2016-01-01

    Surface modification of bioresorbable polymer material (polycaprolactone, PCL) with abnormal glow discharge, initiated during radio-frequency magnetron sputtering of a hydroxyapatite target was investigated. Plasma treatment resulted in an increase of surface roughness of PCL, crystallite size, the surface free energy and hydrophilicity. Increased treatment time (30, 60, 150 seconds) provoked the polymer surface saturation with the sputtering target ions (calcium, phosphorus). The assessment of plasma exposure of PCL surface on bone marrow multipotent mesenchymal stromal cells behavior (BM MSCs) has been performed. Modification of the polymer surface with the abnormal glow discharge stimulated adhesion and subsequent proliferation of BM MSCs; thus, maximum values were achieved with the surface treatment for 60 s. This type of plasma modification did not affect cell viability (apoptosis, necrosis). Thus, the surface modification with abnormal glow discharge, initiated during radio-frequency magnetron sputtering of a hydroxyapatite target, appear to be a promising method of surface modification of bioresorbable polymer material (PCL) for tissue engineering.

  10. Etching mechanism of niobium in coaxial Ar/Cl{sub 2} radio frequency plasma

    SciTech Connect

    Upadhyay, J.; Im, Do; Popović, S.; Vušković, L.; Valente-Feliciano, A.-M.; Phillips, L.

    2015-03-21

    The understanding of the Ar/Cl{sub 2} plasma etching mechanism is crucial for the desired modification of inner surface of the three dimensional niobium (Nb) superconductive radio frequency cavities. Uniform mass removal in cylindrical shaped structures is a challenging task because the etch rate varies along the direction of gas flow. The study is performed in the asymmetric coaxial radio-frequency (rf) discharge with two identical Nb rings acting as a part of the outer electrode. The dependence of etch rate uniformity on pressure, rf power, dc bias, Cl{sub 2} concentration, diameter of the inner electrode, temperature of the outer cylinder, and position of the samples in the structure is determined. To understand the plasma etching mechanisms, we have studied several factors that have important influence on the etch rate and uniformity, which include the plasma sheath potential, Nb surface temperature, and the gas flow rate.

  11. Etching mechanism of niobium in coaxial Ar/Cl2 radio frequency plasma

    SciTech Connect

    Upadhyay, Janardan; Im, Do; Popovic, Svetozar; Valente-Feliciano, Anne -Marie; Phillips, H. Larry; Vuskovic, Leposova

    2015-03-18

    The understanding of the Ar/Cl2 plasma etching mechanism is crucial for the desired modification of inner surface of the three dimensional niobium (Nb) superconductive radio frequency cavities. Uniform mass removal in cylindrical shaped structures is a challenging task because the etch rate varies along the direction of gas flow. The study is performed in the asymmetric coaxial radio-frequency (rf) discharge with two identical Nb rings acting as a part of the outer electrode. The dependence of etch rate uniformity on pressure, rf power, dc bias, Cl2 concentration, diameter of the inner electrode, temperature of the outer cylinder, and position of the samples in the structure is determined. Furthermore, to understand the plasma etching mechanisms, we have studied several factors that have important influence on the etch rate and uniformity, which include the plasma sheath potential, Nb surface temperature, and the gas flow rate.

  12. The 11th Topical Conference on Radio frequency Power in Plasmas. Proceedings

    SciTech Connect

    Prater, R.; Chan, V.S.

    1996-03-01

    The Eleventh Topical Conference on Radio Frequency Power in Plasmas was held in Palm Springs, California under the sponsorship of General Atomics and the American Physical Society. These proceedings represent the papers presented at the Conference. The topics discussed included mode conversion heating and current drive experiments in TFTR, the coupling of high ICRF power in JT{minus}60U(through a 15 cm gap between the antenna and the plasma) as required for ITER, and the H{minus}mode in ASDEX{minus}U, antenna design and technology was discussed in some detail as well as the interaction of plasmas and radio frequency waves for fusion and non{minus}fusion applications. There are 102 papers published in the proceedings and 101 have been abstracted for the Energy Science and Technology database.(AIP)

  13. Numerical simulation of capacitively-coupled, radio-frequency plasma discharges

    NASA Astrophysics Data System (ADS)

    Hammond, Edward Percy, IV

    This research develops a novel, non-dissipative discretization for the drift-diffusion expression of electron flux in capacitively-coupled, radio-frequency plasma discharges. The new discretization is more robust and accurate than commonly used numerical techniques when applied to the solution of the plasma fluid equations. On a relatively coarse grid, the method provides results within a few percent of the grid-converged solution. Low-order upwinding, a common method for discretization of the electron flux; introduces significant robustness. However, on the same coarse grid, the plasma density can differ from the grid-converged result by nearly a factor of two. Another popular discretization of the electron flux is the Scharfetter-Gummel method. Although it is accurate on coarse grids, it is more expensive computationally due to its non-linear nature, and it introduces an additional approximation. It neglects the electron temperature gradient in the flux expression; this can affect the plasma density as much as 20%. A formal method for accelerating the solution towards the periodic, steady-state solution in one and multiple dimensions is also described. Direct integration of the governing equations in time will lead to the harmonic steady-state, but this may require tens or hundreds of thousands of radio-frequency periods when the plasma discharge contains significant neutral species that develop on a time-scale much longer than a radio-frequency period. In contrast, the acceleration scheme can reach the periodic steady-state in a few hundred to a few thousand radio-frequency periods. Previous efforts that used formal acceleration schemes were limited to one dimension. Finally, a fluid model of an argon plasma is developed and compared to experimental data at conditions relevant to low-pressure, capacitively-coupled plasma discharges. The computed results agree reasonably well with the experiments both quantitatively and qualitatively. This model is then used to

  14. Aluminium metallisation of argon and oxygen plasma-modified polycarbonate thin film surfaces

    NASA Astrophysics Data System (ADS)

    Rastomjee, C. S.; Keil, M.; Sotobayashi, H.; Bradshaw, A. M.; Lamont, C. L. A.; Gador, D.; Umbach, E.

    1998-12-01

    The influence of plasma treatment on the metallisation of polycarbonate surfaces was studied using X-ray absorption spectroscopy (XAFS) and core level X-ray photoelectron spectroscopy (XPS). Thin films of two different molecules were chosen: bis-phenol-A polycarbonate with phenol endgroups (P-PC) prepared ex situ by the spin-coating technique onto MoTe 2{0001}surfaces, and the model compound bis-phenol-A polycarbonate ( n=1) with tert-butyl phenyl endgroups (tBP-PC) evaporated in situ in UHV onto Cu{110}, Ag{100} and Ag{111} surfaces with film thicknesses of up to several monolayers. Surfaces of untreated samples and of samples which were pre-treated with either an inert argon or a reactive oxygen microwave plasma were metallised with Al (evaporated by electron beam heating) at film thicknesses ranging from the sub-monolayer region up to several monolayers. For the untreated surface, XAFS and XPS spectra suggest that the Al reacts with the carbonate groups leading to a breaking of the CO double bonds (and/or a reduction in bond order) as well as formation of Al oxide, Al hydroxide and Al-O-C linkages. A study of the time-dependent oxidation of the evaporated Al leads to the conclusion that Al slowly diffuses to the reactive sites in the first few subsurface layers of the polymer. Argon plasma treatment of samples leads to a reduction in the number of carbonyl groups in the near surface region. After metal deposition a higher ratio of metallic, non-reacted, Al was observed covering the polycarbonate surface and the diffusion rate into the polymer bulk seems to be higher than in the case of the untreated surface. Oxygen plasma treatment leads to the creation of additional CO containing species which also react with the Al in the subsequent metallisation process. Here, the ratio of oxidised Al on the polymer surface is higher than observed for untreated and argon plasma pre-treated polymer surfaces.

  15. Pulsed and continuous wave acrylic acid radio frequency plasma deposits: plasma and surface chemistry.

    PubMed

    Voronin, Sergey A; Zelzer, Mischa; Fotea, Catalin; Alexander, Morgan R; Bradley, James W

    2007-04-05

    Plasma polymers have been formed from acrylic acid using a pulsed power source. An on-pulse duration of 100 micros was used with a range of discharge off-times between 0 (continuous wave) and 20,000 micros. X-ray photoelectron spectroscopy (XPS) has been used in combination with trifluoroethanol (TFE) derivatization to quantify the surface concentration of the carboxylic acid functionality in the deposit. Retention of this functionality from the monomer varied from 2% to 65%. When input power was expressed as the time-averaged energy per monomer molecule, E(mean), the deposit chemistry achieved could be described using a single relationship for all deposition conditions. Deposition rates were monitored using a quartz crystal microbalance, which revealed a range from 20 to 200 microg m(-2) s(-1), and these fell as COOH functional retention increased. The flow rate was found to be the major determinant of the deposition rate, rather than being uniquely defined by E(mean), connected to the rate at which fresh monomer enters the system in the monomer deficient regime. The neutral species were collected in a time-averaged manner. As the energy delivered per molecule in the system (E(mean)) decreased, the amount of intact monomer increased, with the average neutral mass approaching 72 amu as E(mean) tends to zero. No neutral oligomeric species were detected. Langmuir probes have been used to determine the temporal evolution of the density and temperature of the electrons in the plasma and the plasma potential adjacent to the depositing film. It has been found that even 500 micros into the afterglow period that ionic densities are still significant, 5-10% of the on-time density, and that ion accelerating sheath potentials fall from 40 V in the on-time to a few volts in the off-time. We have made the first detailed, time- and energy-resolved mass spectrometry measurements in depositing acrylic acid plasma. These have allowed us to identify and quantify the positive ion

  16. Etching of CVD diamond films using oxygen ions in ECR plasma

    NASA Astrophysics Data System (ADS)

    Ma, Zhibin; Wu, Jun; Shen, Wulin; Yan, Lei; Pan, Xin; Wang, Jianhua

    2014-01-01

    Etching with oxygen ions produced by ECR plasma with an asymmetric magnetic mirror field was investigated as a potential technique for polishing CVD diamond. The morphology, structure and roughness of the diamond film surface before and after etching were analyzed respectively using scanning electron microscope (SEM), Raman spectroscopy and surface roughness measuring instrument. It was found that the ridges on diamond surface had been preferentially etched away and thereby the surface roughness decreased from 3.061 to 1.083 μm after 4 h etching. Meanwhile, non-diamond phase appeared on surface and dramatically increased with the extending of etching time. In order to fundamentally understand the etching mechanism, an etching model of diamond film was reasonably proposed on the ground of the experimental results and the theory of plasma physics. The as-generated ions taking screw movement are firstly accelerated along the magnetic field lines in the plasma and collisional presheath, and then deflected from their route towards the diamond film in the MP. When coming into Debye sheath, the motion of ions will be deflected further and strongly accelerated by electric field in the direction normal to the (1 1 1) crystal facets. This process gave rise to energetic ion bombardment towards every (1 1 1) crystal face, and thereby caused preferential etching of pyramidal crystallites.

  17. Oxygen activation at the plasma membrane: relation between superoxide and hydroxyl radical production by isolated membranes.

    PubMed

    Heyno, Eiri; Mary, Véronique; Schopfer, Peter; Krieger-Liszkay, Anja

    2011-07-01

    Production of reactive oxygen species (hydroxyl radicals, superoxide radicals and hydrogen peroxide) was studied using EPR spin-trapping techniques and specific dyes in isolated plasma membranes from the growing and the non-growing zones of hypocotyls and roots of etiolated soybean seedlings as well as coleoptiles and roots of etiolated maize seedlings. NAD(P)H mediated the production of superoxide in all plasma membrane samples. Hydroxyl radicals were only produced by the membranes of the hypocotyl growing zone when a Fenton catalyst (FeEDTA) was present. By contrast, in membranes from other parts of the seedlings a low rate of spontaneous hydroxyl radical formation was observed due to the presence of small amounts of tightly bound peroxidase. It is concluded that apoplastic hydroxyl radical generation depends fully, or for the most part, on peroxidase localized in the cell wall. In soybean plasma membranes from the growing zone of the hypocotyl pharmacological tests showed that the superoxide production could potentially be attributed to the action of at least two enzymes, an NADPH oxidase and, in the presence of menadione, a quinone reductase.

  18. Trapped electron plasma formation and equilibrium with a low-power radio-frequency drive

    SciTech Connect

    Romé, M.; Maero, G.; Paroli, B.; Pozzoli, R.; Chen, S.

    2015-06-29

    Penning-Malmberg traps confining electron plasmas usually rely on external sources like thermo- and photocathodes. It has been already demonstrated that electron plasmas of comparable densities can be produced by applying a radio-frequency (RF) power to any inner electrode of the trap. Such excitation may result in significant electron heating and ionization of the residual gas with the formation of a plasma column when the RF frequency is of the order or larger than the typical axial bounce frequencies of few-eV electrons, even at RF amplitude of few volts. While discharges are common in plasma generation at higher pressures and RF power, this mechanism is not yet well explored in our working conditions, namely ultra-high vacuum and very low RF power. This plasma production mechanism is very sensitive to the experimental conditions. Interesting phenomena can be observed: transition from a diffuse to a narrow-section, denser plasma column; presence of low-order diocotron modes in transient and steady-state plasmas; modulation of the m=1 diocotron mode and suppression of its instability despite the presence of positive ions and resistive loads. These observations are reported here, and possible explanations are discussed. In addition, a possible electron heating mechanism is investigated with a single-particle, one-dimensional model described by an area-preserving map where an electron bounces within a square potential well and the RF excitation is modelled by a time-oscillating square barrier. The low-energy part of the Poincaré plot includes both quasi-periodic and chaotic regions, where heating up to ionization energies is achievable. Results of a systematic analysis of the map extracting its chaotic properties and scaling laws as a function of the control parameters are reported.

  19. Trapped electron plasma formation and equilibrium with a low-power radio-frequency drive

    NASA Astrophysics Data System (ADS)

    Romé, M.; Chen, S.; Maero, G.; Paroli, B.; Pozzoli, R.

    2015-06-01

    Penning-Malmberg traps confining electron plasmas usually rely on external sources like thermo- and photocathodes. It has been already demonstrated that electron plasmas of comparable densities can be produced by applying a radio-frequency (RF) power to any inner electrode of the trap. Such excitation may result in significant electron heating and ionization of the residual gas with the formation of a plasma column when the RF frequency is of the order or larger than the typical axial bounce frequencies of few-eV electrons, even at RF amplitude of few volts. While discharges are common in plasma generation at higher pressures and RF power, this mechanism is not yet well explored in our working conditions, namely ultra-high vacuum and very low RF power. This plasma production mechanism is very sensitive to the experimental conditions. Interesting phenomena can be observed: transition from a diffuse to a narrow-section, denser plasma column; presence of low-order diocotron modes in transient and steady-state plasmas; modulation of the m=1 diocotron mode and suppression of its instability despite the presence of positive ions and resistive loads. These observations are reported here, and possible explanations are discussed. In addition, a possible electron heating mechanism is investigated with a single-particle, one-dimensional model described by an area-preserving map where an electron bounces within a square potential well and the RF excitation is modelled by a time-oscillating square barrier. The low-energy part of the Poincaré plot includes both quasi-periodic and chaotic regions, where heating up to ionization energies is achievable. Results of a systematic analysis of the map extracting its chaotic properties and scaling laws as a function of the control parameters are reported.

  20. Study on structural, morphological and thermal properties of surface modified polyvinylchloride (PVC) film under air, argon and oxygen discharge plasma

    NASA Astrophysics Data System (ADS)

    Suganya, Arjunan; Shanmugavelayutham, Gurusamy; Serra Rodríguez, Carmen

    2016-09-01

    The effect of air, argon, oxygen DC glow discharge plasma on the polyvinylchloride (PVC) film synthesized by solution casting technique, were evaluated via changes in physio-chemical properties such as structural, morphological, crystalline, thermal properties. The PVC film was plasma treated as a function of exposure time and different plasma forming gases, while other operating parameters such as power and pressure remained constant at 100 W and 2 Pa respectively. The plasma treated PVC were characterized by static contact angle, ATR-FTIR, XPS, AFM and T-peel analysis. It was found that various gaseous plasma treatments have improved the polar components, surface roughness on the surface of PVC which was confirmed by XPS, AFM, resulting in highly enhanced wettability and adhesion. X-ray diffraction study showed that plasma treatment does not persuade considerable change, even though it vaguely induces the crystallinity. The thermal properties of plasma treated PVC were evaluated by Differential Scanning Calorimetry and it was observed that O2 plasma treatment gives higher glass transition temperature of 87.21 °C compared with the untreated one. The glass transition temperature slightly increased for Oxygen plasma treated material due to the presence of higher concentration of the polar functional groups on the PVC surface due to strong intramolecular bonding.

  1. Reactive hydroxyl radical-driven oral bacterial inactivation by radio frequency atmospheric plasma

    NASA Astrophysics Data System (ADS)

    Kang, Sung Kil; Choi, Myeong Yeol; Koo, Il Gyo; Kim, Paul Y.; Kim, Yoonsun; Kim, Gon Jun; Mohamed, Abdel-Aleam H.; Collins, George J.; Lee, Jae Koo

    2011-04-01

    We demonstrated bacterial (Streptococcus mutans) inactivation by a radio frequency power driven atmospheric pressure plasma torch with H2O2 entrained in the feedstock gas. Optical emission spectroscopy identified substantial excited state •OH generation inside the plasma and relative •OH formation was verified by optical absorption. The bacterial inactivation rate increased with increasing •OH generation and reached a maximum 5-log10 reduction with 0.6% H2O2 vapor. Generation of large amounts of toxic ozone is drawback of plasma bacterial inactivation, thus it is significant that the ozone concentration falls within recommended safe allowable levels with addition of H2O2 vapor to the plasma.

  2. Microwave frequency sweep interferometer for plasma density measurements in ECR ion sources: Design and preliminary results

    SciTech Connect

    Torrisi, Giuseppe; Mascali, David; Neri, Lorenzo; Leonardi, Ornella; Celona, Luigi; Castro, Giuseppe; Agnello, Riccardo; Caruso, Antonio; Passarello, Santi; Longhitano, Alberto; Gammino, Santo; Sorbello, Gino; Isernia, Tommaso

    2016-02-15

    The Electron Cyclotron Resonance Ion Sources (ECRISs) development is strictly related to the availability of new diagnostic tools, as the existing ones are not adequate to such compact machines and to their plasma characteristics. Microwave interferometry is a non-invasive method for plasma diagnostics and represents the best candidate for plasma density measurement in hostile environment. Interferometry in ECRISs is a challenging task mainly due to their compact size. The typical density of ECR plasmas is in the range 10{sup 11}–10{sup 13} cm{sup −3} and it needs a probing beam wavelength of the order of few centimetres, comparable to the chamber radius. The paper describes the design of a microwave interferometer developed at the LNS-INFN laboratories based on the so-called “frequency sweep” method to filter out the multipath contribution in the detected signals. The measurement technique and the preliminary results (calibration) obtained during the experimental tests will be presented.

  3. Reactive hydroxyl radical-driven oral bacterial inactivation by radio frequency atmospheric plasma

    SciTech Connect

    Kang, Sung Kil; Lee, Jae Koo; Choi, Myeong Yeol; Koo, Il Gyo; Kim, Paul Y.; Kim, Yoonsun; Kim, Gon Jun; Collins, George J.; Mohamed, Abdel-Aleam H.

    2011-04-04

    We demonstrated bacterial (Streptococcus mutans) inactivation by a radio frequency power driven atmospheric pressure plasma torch with H{sub 2}O{sub 2} entrained in the feedstock gas. Optical emission spectroscopy identified substantial excited state OH generation inside the plasma and relative OH formation was verified by optical absorption. The bacterial inactivation rate increased with increasing OH generation and reached a maximum 5-log{sub 10} reduction with 0.6%H{sub 2}O{sub 2} vapor. Generation of large amounts of toxic ozone is drawback of plasma bacterial inactivation, thus it is significant that the ozone concentration falls within recommended safe allowable levels with addition of H{sub 2}O{sub 2} vapor to the plasma.

  4. Self-compensated standing wave probe for characterization of radio-frequency plasmas.

    PubMed

    Sung, Ta-Lun; Matsumura, Shosaku; Teii, Kungen; Teii, Shinriki

    2014-06-01

    A simple self-compensated Langmuir probe using the character of a standing wave is developed for characterization of radio-frequency (RF) discharge plasmas. This probe is based on a concept that the interference of RF field is eliminated at the node of a standing wave which exists ideally at one-fourth of the RF wavelength (λ/4) away from the probe tip in the plasma. The fluctuation of plasma space potential is suppressed as confirmed by comparison with a non-compensated probe and a self-compensated probe using an inductor-capacitor (LC) resonant circuit. The plasma parameters obtained with the standing wave probe are in agreement with those with the LC resonant probe within discrepancy of 15% indicating high reliability of the results.

  5. On quasi-thermal fluctuations near the plasma frequency in the outer plasmasphere: A case study

    NASA Technical Reports Server (NTRS)

    Lund, E. J.; Labelle, J.; Treumann, R. A.

    1994-01-01

    We present a derivation of the quasi-thermal electrostatic fluctuation power spectrum in a mult-Maxwellian plasma and show sample calculated spectra. We then apply this theory, which has been successfully applied in oter regions of space, to spectra from two Active Magnetospheric Particle Tracer Explorer/Ion Release Module (AMPTER IRM) passes through the duskside plasmasphere. WE show that the plasma line that is often seen in this region is usually quasi-thermal in origin. We obtain a refined estimate of the plasma frequency and infer a cold electron temperature which is consistent within a factor of 2 with both models and previous meausurements by other techniques, but closer investigation reveals that details of the plasma line cannot be explained with the ususal two isotropic Maxwellian model.

  6. Superhydrophilic poly(L-lactic acid) electrospun membranes for biomedical applications obtained by argon and oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Correia, D. M.; Ribeiro, C.; Botelho, G.; Borges, J.; Lopes, C.; Vaz, F.; Carabineiro, S. A. C.; Machado, A. V.; Lanceros-Méndez, S.

    2016-05-01

    Poly(L-lactic acid), PLLA, electrospun membranes and films were plasma treated at different times and power with argon (Ar) and oxygen (O2), independently, in order to modify the hydrophobic nature of the PLLA membranes. Both Ar and O2 plasma treatments promote an increase in fiber average size of the electrospun membranes from 830 ± 282 nm to 866 ± 361 and 1179 ± 397 nm, respectively, for the maximum exposure time (970 s) and power (100 W). No influence of plasma treatment was detected in the physical-chemical characteristics of PLLA, such as chemical structure, polymer phase or degree of crystallinity. On the other hand, an increase in the roughness of the films was obtained both with argon and oxygen plasma treatments. Surface wettability studies revealed a decrease in the contact angle with increasing plasma treatment time for a given power and with increasing power for a given time in membranes and films and superhydrophilic electrospun fiber membranes were obtained. Results showed that the argon and oxygen plasma treatments can be used to tailor hydrophilicity of PLLA membranes for biomedical applications. MTT assay results indicated that plasma treatments under Ar and O2 do not influence the metabolic activity of MC3T3-E1 pre-osteoblast cells.

  7. Kinetic theory of low-frequency cross-field instability in a weakly ionized plasma. II

    SciTech Connect

    Dimant, Y.S.; Sudan, R.N.

    1995-04-01

    The consistent kinetic approach developed in Paper I [Ya. S. Dimant and R. N. Sudan, Phys. Plasmas {bold 2}, 1157 (1995)] is applied to obtain the general dispersion relation of the two-stream {bold E}{times}{bold B} instability in collisionally dominated weakly ionized plasmas for wave frequencies small compared to the ion--neutral collision frequency. This dispersion relation covers the whole low-frequency band from the asymptotic short-wave limit studied in Paper I to the long-wave limit. Previous theories employing simplified kinetic theory or fluid equations for electron behavior are only correct in the long-wave limit. The principal new results are that the threshold conditions for this instability and the growth rates are altered from those predicted by earlier simplified theories. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  8. Low and high frequency instabilities in an explosion-generated-plasma and possibility of wave triplet

    NASA Astrophysics Data System (ADS)

    Malik, O. P.; Singh, Sukhmander; Malik, Hitendra K.; Kumar, A.

    2015-01-01

    An explosion-generated-plasma is explored for low and high frequency instabilities by taking into account the drift of all the plasma species together with the dust particles which are charged. The possibility of wave triplet is also discussed based on the solution of dispersion equation and synchronism conditions. High frequency instability (HFI) and low frequency instability (LFI) are found to occur in this system. LFI grows faster with the higher concentration of dust particles, whereas its growth rate goes down if the mass of the dust is higher. The ion and electron temperatures affect its growth in opposite manner and the electron temperature causes this instability to grow. In addition to the instabilities, a simple wave is also observed to propagate, whose velocity is larger for larger wave number, smaller mass of the dust and higher ion temperature.

  9. Characterization of oxygenated metabolites of ginsenoside Rg1 in plasma and urine of rat.

    PubMed

    Wang, Jing-Rong; Tong, Tian-Tian; Yau, Lee-Fong; Chen, Cheng-Yu; Bai, Li-Ping; Ma, Jing; Hu, Ming; Liu, Liang; Jiang, Zhi-Hong

    2016-07-15

    This study describes the characterization of oxygenated metabolites of ginsenoside Rg1 in rat urine and plasma. These in vivo metabolites were profiled by using UHPLC-QTOF MS-based method. On the basis of high-resolution MS/MS data, and comparison with chemically synthesized authentic compounds, nine oxygenated metabolites of Rg1 were characterized as vinaginsenosides 21 and 22 (M1 and M2), vinaginsenoside R15 (M3), 6-O-(β-d-glucopyranosyl)-20-O-(β-d-glucopyranosyl) 3β, 6α, 12β, 20(S)-tetrahydroxy-24ξ-hydroxydammar-25-ene (M4 and M5), floralginsenoside A (M7 and M8), floralginsenoside B (M9) and epoxyginsenoside Rg1 (M13), respectively. Among these metabolites, M4, M5 and M13 are new ginsenosides and others were detected as in vivo metabolites of Rg1 for the first time. In addition, a series of oxygenated metabolites of Rh1 and deglycosylated metabolite of Rg1, were observed and characterized by comparing with compounds synthesized by us, which revealed an association between C-20 configuration and the extent of oxidation metabolism. Appearance of all these metabolites in blood stream and urine after i.v. dosing and oral administration of Rg1 was further examined, which clearly showed that mono-oxygenated metabolites of Rg1 were major circulating metabolites at the early stage after dosing. Characterization of exact chemical structures of these circulating metabolites contribute greatly to our understanding of chemical exposure after consumption of ginseng products, and provide valuable information for explaining multiple bioactivities of ginseng products.

  10. Surface Modification of C3N4 through Oxygen-Plasma Treatment: A Simple Way toward Excellent Hydrophilicity.

    PubMed

    Bu, Xiuming; Li, Jipeng; Yang, Siwei; Sun, Jing; Deng, Yuan; Yang, Yucheng; Wang, Gang; Peng, Zheng; He, Peng; Wang, Xianying; Ding, Guqiao; Yang, Junhe; Xie, Xiaoming

    2016-11-16

    We developed a universal method to prepare hydrophilic carbon nitrogen (C3N4) nanosheets. By treating C3N4 nanosheets with oxygen plasma, hydroxylamine groups (N-OH) with intense protonation could be introduced on the surface; moreover, the content of N-OH groups increased linearly with the oxygen-plasma treatment time. Thanks to the excellent hydrophilicity, uniformly dispersed C3N4 solution were prepared, which was further translated into C3N4 paper by simple vacuum filtration. Pure C3N4 paper with good stability, excellent hydrophilicity, and biocompatibility were proved to have excellent performance in tissue repair. Further research demonstrated that the oxygen-plasma treatment method can also introduce N-OH groups into other nitrogen-containing carbon materials (NCMs) such as N-doped graphene, N-doped carbon nanotube, and C2N, which offers a new perspective on the surface modification and functionalization of these carbon nanomaterials.

  11. Raman spectra investigation of the defects of chemical vapor deposited multilayer graphene and modified by oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Li, Zongyao; Xu, Yu; Cao, Bing; Qi, Lin; He, Shunyu; Wang, Chinhua; Zhang, Jicai; Wang, Jianfeng; Xu, Ke

    2016-11-01

    Graphene, a two dimensional material, can be modified its properties by defects engineering. Here, we present Raman spectra studies of the multilayer graphene (MLG) fabricated by low-pressure chemical vapor deposition over copper foil, and report that the defects of MLG can be controlled by adjusting methane concentration. Moreover, MLG can be changed from metallic to semiconductoring properties by using oxygen plasma treatment, and we investigate the defects evolution of the graphene after exposing to oxygen plasma by Raman spectra. Our results indicate that the amount of defects in graphene can be changed by regulating the methane concentration and oxygen plasma exposure times, but the primary type of defect in MLG is still boundary-like defect. It is valuable for understanding the physics of defects evolution through artificially generated defects, and such defect engineering will greatly open up the future application of the novel material.

  12. Powerful single-frequency CO/sub 2/ laser for plasma diagnostics

    SciTech Connect

    Takahashi, H.; Kimura, M.; Morita, Y.; Sano, R.

    1984-10-01

    A cw 240-W CO/sub 2/ laser has been developed for plasma scattering measurements. The laser oscillates only on the 10P(20) transition (10.5912-..mu..m wavelength) at a single longitudinal as well as transverse mode with linear polarization. These properties are obtained by using an adequately long cavity with a folded beam configuration. Part of the output beam was heterodyned with a local oscillator laser to confirm the single-frequency oscillation. The short-term frequency stability was 200 kHz (7 x 10/sup -9/) for an observation time of 1/15 s. The shift of the oscillating frequency due to the discharge current was 360 kHz/mA and the frequency shift due to the total gas pressure was 4.1 MHz/Torr. These frequency shifts are mostly attributable to the change of the refractive index of the laser gas.

  13. Combining oxygen plasma treatment with anchorage of cationized gelatin for enhancing cell affinity of poly(lactide-co-glycolide).

    PubMed

    Shen, Hong; Hu, Xixue; Yang, Fei; Bei, Jianzhong; Wang, Shenguo

    2007-10-01

    Surface characteristics greatly influence attachment and growth of cells on biomaterials. Although polylactone-type biodegradable polymers have been widely used as scaffold materials for tissue engineering, lack of cell recognition sites, poor hydrophilicity and low surface energy lead to a bad cell affinity of the polymers, which limit the usage of polymers as scaffolds in tissue engineering. In the present study, surface of poly (L-lactide-co-glycolide) (PLGA) was modified by a method of combining oxygen plasma treatment with anchorage of cationized gelatin. Modification effect of the method was compared with other methods of oxygen plasma treatment, cationized gelatin or gelatin coating and combining oxygen plasma treatment with anchorage of gelatin. The change of surface property was compared by contact angles, surface energy, X-ray photoelectron spectra (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM) measurement. The optimum oxygen pretreatment time determined by surface energy was 10 min when the power was 50 W and the oxygen pressure was 20 Pa. Analysis of the stability of gelatin and cationized gelatin anchored on PLGA by XPS, ATR-FTIR, contact angles and surface energy measurement indicated the cationized gelatin was more stable than gelatin. The result using mouse NIH 3T3 fibroblasts as model cells to evaluate cell affinity in vitro showed the cationized gelatin-anchored PLGA (OCG-PLGA) was more favorable for cell attachment and growth than oxygen plasma treated PLGA (O-PLGA) and gelatin-anchored PLGA (OG-PLGA). Moreover cell affinity of OCG-PLGA could match that of collagen-anchored PLGA (AC-PLGA). So the surface modification method combining oxygen plasma treatment with anchorage of cationized gelatin provides a universally effective way to enhance cell affinity of polylactone-type biodegradable polymers.

  14. Measurement of high-frequency density fluctuations in improved confinement RFP plasmas

    NASA Astrophysics Data System (ADS)

    Duff, J. R.; Chapman, B. E.; Anderson, J. K.; Sarff, J. S.; Lin, L.; Ding, W. X.; Brower, D. L.

    2013-10-01

    In standard RFP plasmas, transport is dominated by global magnetic tearing modes. For improved-confinement plasmas using inductive current profile control (PPCD), smaller-scale fluctuations at higher frequencies (>50 kHz) may become more important as the global tearing modes are significantly reduced. In particular, drift-wave-like instabilities are theoretically unstable to the higher temperature and density gradients achieved during PPCD discharges. On the MST, an eleven chord Far-Infrared (FIR) laser-based diagnostic system with ~ 8 cm spacing is used to measure electron density fluctuations by interferometry and far-forward collective scattering. The existing diagnostic measures line-integrated density fluctuations within the divergence of the probe beam covering a wavenumber range k-< 1.3 cm-1, corresponding to k-ρs < 1.3 (ρs is the ion-sound Larmor radius). Experimentally, in PPCD plasmas, global tearing modes are reduced while high frequency coherent modes (50 < f < 140 kHz) emerge among broadband fluctuations. Correlations of these modes with sources of free energy, such as temperature and density gradients, will be investigated. Additionally, effects of increased plasma flow from a 1MW tangential NBI on high frequency density fluctuations will also be explored. Work Supported by U.S.D.O.E.

  15. Use of the absolute phase in frequency modulated continuous wave plasma reflectometry

    SciTech Connect

    Cunningham, G.

    2008-08-15

    In frequency modulated continuous wave reflectometry, used for density profile measurement in fusion plasmas, it is usual to measure the beat frequency between the launched wave and the reflected wave, and from this to calculate the position of the reflecting layer in the plasma. The absolute phase of the beat signal is usually neglected. The reason is that the phase shift between sweeps is usually comparable with or more than 2{pi}, leading to an ambiguity that is impossible to resolve. However, recent observations on the MAST tokamak have shown that, under quiet plasma conditions (this term has to be defined), the phase shift between sweeps is small compared with 2{pi} and the phase ambiguity can be readily resolved. The reflectometer signal is then being analyzed as an interferometer signal would normally be, and there is a substantial improvement in spatial resolution. The method is illustrated by application to small edge localized mode precursor and allows what is believed to be the first quantitative measurement of the displacement of the plasma boundary by such a precursor mode. The errors in both the absolute phase measurement and the more conventional frequency measurement are also estimated.

  16. Irradiation of silver and agar/silver nanoparticles with argon, oxygen glow discharge plasma, and mercury lamp.

    PubMed

    Ahmad, Mahmoud M; Abdel-Wahab, Essam A; El-Maaref, A A; Rawway, Mohammed; Shaaban, Essam R

    2014-01-01

    The irradiation effect of argon, oxygen glow discharge plasma, and mercury lamp on silver and agar/silver nanoparticle samples is studied. The irradiation time dependence of the synthesized silver and agar/silver nanoparticle absorption spectra and their antibacterial effect are studied and compared. In the agar/silver nanoparticle sample, as the irradiation time of argon glow discharge plasma or mercury lamp increases, the peak intensity and the full width at half maximum, FWHM, of the surface plasmon resonance absorption band is increased, however a decrease of the peak intensity with oxygen glow plasma has been observed. In the silver nanoparticle sample, as the irradiation time of argon, oxygen glow discharge plasma or mercury lamp increases, the peak intensity of the surface plasmon resonance absorption band is increased, however, there is no significant change in the FWHM of the surface plasmon resonance absorption band. The SEM results for both samples showed nanoparticle formation with mean size about 50 nm and 40 nm respectively. Throughout the irradiation time with the argon, oxygen glow discharge plasma or mercury lamp, the antibacterial activity of several kinds of Gram-positive and Gram-negative bacteria has been examined.

  17. Low-frequency plasma conductivity in the average-atom approximation.

    PubMed

    Kuchiev, M Yu; Johnson, W R

    2008-08-01

    Low-frequency properties of a plasma are examined within the average-atom approximation, which presumes that scattering of a conducting electron on each atom takes place independently of other atoms. The relaxation time tau distinguishes a high-frequency region omegatau>1 , where the single-atom approximation is applicable explicitly, from extreme low frequencies omegatau<1 , where, naively, the single-atom approximation is invalid. A proposed generalization of the formalism, which takes into account many-atom collisions, is found to be accurate in all frequency regions, from omega=0 to omegatau>1 , reproducing the Ziman formula in the static limit, results based on the Kubo-Greenwood formula for high frequencies and satisfying the conductivity sum rule precisely. The correspondence between physical processes leading to the conventional Ohm's law and the infrared properties of QED is discussed. The suggested average-atom approach to frequency-dependent conductivity is illustrated by numerical calculations for an aluminum plasma in the temperature range 2-10eV .

  18. Charge state distribution studies of pure and oxygen mixed krypton ECR plasma - signature of isotope anomaly and gas mixing effect.

    PubMed

    Kumar, Pravin; Mal, Kedar; Rodrigues, G

    2016-11-01

    We report the charge state distributions of the pure, 25% and 50% oxygen mixed krypton plasma to shed more light on the understanding of the gas mixing and the isotope anomaly [A. G. Drentje, Rev. Sci. Instrum. 63 (1992) 2875 and Y Kawai, D Meyer, A Nadzeyka, U Wolters and K Wiesemann, Plasma Sources Sci. Technol. 10 (2001) 451] in the electron cyclotron resonance (ECR) plasmas. The krypton plasma was produced using a 10 GHz all-permanent-magnet ECR ion source. The intensities of the highly abundant four isotopes, viz. (82) Kr (~11.58%), (83) Kr (~11.49%), (84) Kr (~57%) and (86) Kr (17.3%) up to ~ +14 charge state have been measured by extracting the ions from the plasma and analysing them in the mass and the energy using a large acceptance analyzer-cum-switching dipole magnet. The influence of the oxygen gas mixing on the isotopic krypton ion intensities is clearly evidenced beyond +9 charge state. With and without oxygen mixing, the charge state distribution of the krypton ECR plasma shows the isotope anomaly with unusual trends. The anomaly in the intensities of the isotopes having quite closer natural abundance, viz. (82) Kr, (86) Kr and (83) Kr, (86) Kr is prominent, whereas the intensity ratio of (86) Kr to (84) Kr shows a weak signature of it. The isotope anomaly tends to disappear with increasing oxygen mixing in the plasma. The observed trends in the intensities of the krypton isotopes do not follow the prediction of linear Landau wave damping in the plasma. Copyright © 2016 John Wiley & Sons, Ltd.

  19. Cellular-automata model of oxygen plasma impact on porous low-K dielectric

    NASA Astrophysics Data System (ADS)

    Rezvanov, Askar; Matyushkin, Igor V.; Gutshin, Oleg P.; Gornev, Evgeny S.

    2016-12-01

    Cellular-automata model of oxygen plasma influence on the integral properties of porous low-K dielectric is studied. The present work investigates the imitative simulation of this process. In our model we consider one isolated pore, which is simulated by cylinder with length L=200 nm and radius 1 nm ignoring the curvature factor. The simulation was performed for 2 million automata steps that correspond to 2 seconds in the real process time. Extrapolating the data to the longer time shows that more and more •CH3 groups will be replaced by the •OH groups, and over time almost all methyl groups will leave the pore surface (there is not more than 20% of the initial methyl groups amount on the first low-K dielectric 40nm after 2 seconds simulation).

  20. Electron energy distribution functions in low-pressure oxygen plasma columns sustained by propagating surface waves

    SciTech Connect

    Stafford, L.; Margot, J.; Moisan, M.; Khare, R.; Donnelly, V. M.

    2009-01-12

    Electron energy distribution functions (EEDFs) were measured in a 50 mTorr oxygen plasma column sustained by propagating surface waves. Trace-rare-gas-optical-emission spectroscopy was used to derive EEDFs by selecting lines to extract ''electron temperature''(T{sub e}) corresponding to either lower energy electrons that excite high-lying levels through stepwise excitation via metastable states or higher energy electrons that excite emission directly from the ground state. Lower energy T{sub e}'s decreased from 8 to 5.5 eV with distance from the wave launcher, while T{sub e}{approx_equal}6 eV for higher energy electrons and T{sub e}>20 eV for a high-energy tail. Mechanisms for such EEDFs are discussed.

  1. The adhesion of oxygen-plasma treated poly(ethylene) and poly(ethylene terephthlate) films

    SciTech Connect

    Holton, S.L.; Kinloch, A.J.; Watts, J.F.

    1996-12-31

    The effects of low-pressure oxygen-plasma treatment on the surfaces of poly(ethylene) (PE) and poly(ethylene terephthlate) (PET) films and its influence on the adhesion of PE/PET laminates were assessed. The 90{degree} peel test was used to estimate the adhesive fracture energy, G{sub c} for the laminates. XPS, SEM and AFM were used to analyse the treated films and fracture surfaces. Significant improvements in bond strength occurred within very short treatment times (5s at 50W) with the maximum adhesion occurring after 300s. For longer treatment times the bond strengths decrease slightly. G{sub c} values were found to be low when PET was the peel arm. When PE was the peel arm, the G{sub c} values were substantially larger using the current analysis.

  2. Improving the electrical performance of MoS2 by mild oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Nan, Haiyan; Wu, Zhangting; Jiang, Jie; Zafar, Amina; You, Yumeng; Ni, Zhenhua

    2017-04-01

    Two-dimensional (2D) molybdenum disulfide (MoS2) is considered as a promising candidate for electronic and optoelectronic devices. However, structural defects in MoS2 are widely reported and can greatly degrade its electrical and optical properties. In this work, we investigate the structural defects in MoS2 by low temperature photoluminescence (PL) spectroscopy and study their effects on the electrical performance, i.e. carrier mobility. We also adopt the mild oxygen plasma treatment to repair the structural defects and found that the carrier mobility of monolayer MoS2 can be greatly improved. This work would therefore offer a practical route to improve the performance of 2D dichalcogenide-based electrical and optoelectronic devices.

  3. Power supply and impedance matching to drive technological radio-frequency plasmas with customized voltage waveforms.

    PubMed

    Franek, James; Brandt, Steven; Berger, Birk; Liese, Martin; Barthel, Matthias; Schüngel, Edmund; Schulze, Julian

    2015-05-01

    We present a novel radio-frequency (RF) power supply and impedance matching to drive technological plasmas with customized voltage waveforms. It is based on a system of phase-locked RF generators that output single frequency voltage waveforms corresponding to multiple consecutive harmonics of a fundamental frequency. These signals are matched individually and combined to drive a RF plasma. Electrical filters are used to prevent parasitic interactions between the matching branches. By adjusting the harmonics' phases and voltage amplitudes individually, any voltage waveform can be approximated as a customized finite Fourier series. This RF supply system is easily adaptable to any technological plasma for industrial applications and allows the commercial utilization of process optimization based on voltage waveform tailoring for the first time. Here, this system is tested on a capacitive discharge based on three consecutive harmonics of 13.56 MHz. According to the Electrical Asymmetry Effect, tuning the phases between the applied harmonics results in an electrical control of the DC self-bias and the mean ion energy at almost constant ion flux. A comparison with the reference case of an electrically asymmetric dual-frequency discharge reveals that the control range of the mean ion energy can be significantly enlarged by using more than two consecutive harmonics.

  4. Power supply and impedance matching to drive technological radio-frequency plasmas with customized voltage waveforms

    NASA Astrophysics Data System (ADS)

    Franek, James; Brandt, Steven; Berger, Birk; Liese, Martin; Barthel, Matthias; Schüngel, Edmund; Schulze, Julian

    2015-05-01

    We present a novel radio-frequency (RF) power supply and impedance matching to drive technological plasmas with customized voltage waveforms. It is based on a system of phase-locked RF generators that output single frequency voltage waveforms corresponding to multiple consecutive harmonics of a fundamental frequency. These signals are matched individually and combined to drive a RF plasma. Electrical filters are used to prevent parasitic interactions between the matching branches. By adjusting the harmonics' phases and voltage amplitudes individually, any voltage waveform can be approximated as a customized finite Fourier series. This RF supply system is easily adaptable to any technological plasma for industrial applications and allows the commercial utilization of process optimization based on voltage waveform tailoring for the first time. Here, this system is tested on a capacitive discharge based on three consecutive harmonics of 13.56 MHz. According to the Electrical Asymmetry Effect, tuning the phases between the applied harmonics results in an electrical control of the DC self-bias and the mean ion energy at almost constant ion flux. A comparison with the reference case of an electrically asymmetric dual-frequency discharge reveals that the control range of the mean ion energy can be significantly enlarged by using more than two consecutive harmonics.

  5. Green frequency-doubled laser-beam propagation in high-temperature hohlraum plasmas.

    PubMed

    Niemann, C; Berger, R L; Divol, L; Froula, D H; Jones, O; Kirkwood, R K; Meezan, N; Moody, J D; Ross, J; Sorce, C; Suter, L J; Glenzer, S H

    2008-02-01

    We demonstrate propagation and small backscatter losses of a frequency-doubled (2omega) laser beam interacting with inertial confinement fusion hohlraum plasmas. The electron temperature of 3.3 keV, approximately a factor of 2 higher than achieved in previous experiments with open geometry targets, approaches plasma conditions of high-fusion yield hohlraums. In this new temperature regime, we measure 2omega laser-beam transmission approaching 80% with simultaneous backscattering losses of less than 10%. These findings suggest that good laser coupling into fusion hohlraums using 2omega light is possible.

  6. Nonlinear low-frequency electrostatic wave dynamics in a two-dimensional quantum plasma

    SciTech Connect

    Ghosh, Samiran; Chakrabarti, Nikhil

    2016-08-15

    The problem of two-dimensional arbitrary amplitude low-frequency electrostatic oscillation in a quasi-neutral quantum plasma is solved exactly by elementary means. In such quantum plasmas we have treated electrons quantum mechanically and ions classically. The exact analytical solution of the nonlinear system exhibits the formation of dark and black solitons. Numerical simulation also predicts the possible periodic solution of the nonlinear system. Nonlinear analysis reveals that the system does have a bifurcation at a critical Mach number that depends on the angle of propagation of the wave. The small-amplitude limit leads to the formation of weakly nonlinear Kadomstev–Petviashvili solitons.

  7. Scattering of radio frequency waves by cylindrical density filaments in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Ram, Abhay K.; Hizanidis, Kyriakos

    2016-02-01

    In tokamak fusion plasmas, coherent fluctuations in the form of blobs or filaments are routinely observed in the scrape-off layer. Radio frequency (RF) electromagnetic waves, excited by antenna structures placed near the wall of a tokamak, have to propagate through the scrape-off layer before reaching the core of the plasma. While the effect of fluctuations on the properties of RF waves has not been quantified experimentally, it is of interest to carry out a theoretical study to determine if fluctuations can affect the propagation characteristics of RF waves. Usually, the difference between the plasma density inside the filament and the background plasma density is sizable, the ratio of the density difference to the background density being of order one. Generally, this precludes the use of geometrical optics in determining the effect of fluctuations, since the relevant ratio has to be much less than one, typically, of the order of 10% or less. In this paper, a full-wave, analytical model is developed for the scattering of a RF plane wave by a cylindrical plasma filament. It is assumed that the plasma inside and outside the filament is cold and uniform and that the major axis of the filament is aligned along the toroidal magnetic field. The ratio of the density inside the filament to the density of the background plasma is not restricted. The theoretical framework applies to the scattering of any cold plasma wave. In order to satisfy the boundary conditions at the interface between the filament and the background plasma, the electromagnetic fields inside and outside the filament need to have the same k∥ , the wave vector parallel to the ambient magnetic field, as the incident plane wave. Consequently, in contrast to the scattering of a RF wave by a spherical blob [Ram et al., Phys. Plasmas 20, 056110-1-056110-10 (2013)], the scattering by a field-aligned filament does not broaden the k∥ spectrum. However, the filament induces side-scattering leading to surface

  8. Competitive Low Pressure Oxygen Plasma Interactions with Different= Carbon-Carbon Double Bonds

    NASA Astrophysics Data System (ADS)

    Patiño, P.; Sifontes, A.; Gambús, G.

    1999-10-01

    Recently we have shown advances from reactions of O(^3P) with both, l ong-chain hydrocarbons and refinery residuum. The oxidation products of t he process, a mixture of alcohols, epoxides and carbonyl compounds, might have potential properties as additives in formulating fuels. This work s hows the results of the interactions of an oxygen plasma with double bond s, both olefin and aromatic, in the same compound. The reactions have bee n carried out by making the plasma, created by a high voltage glow discha rge, reach the low vapor pressure surface of liquid 4-phenyl-1-butene. Th is (3 mL) was cooled down to -45 ^oC in a glass reactor, applied power was 24 W, at an oxygen pressure of 20 Pa. Products were analyzed by IR, N MR and mass spectroscopies. Conversions were studied as a function of the reaction time, this ranging from 5 to 120 minutes. At short times the O( ^3P) atoms produced in the discharge only reacted with the alkene fra ction of the hydrocarbon, 4-phenyl-1,2-epoxibutane (52%) and 4-phenyl-bu tanal (48%) being the products. Reactions on the benzene ring were obser ved from about 30 minutes on, the corresponding phenols having being prod uced at ratios ortho:para:meta :: 4:1:0.7. At 120 minutes, the ol efin have been completely oxidized and a low fraction of the non-equivale nt two methylene groups have reacted to produce alcohols and ketones.

  9. Evaluation of fatty acid oxidation by reactive oxygen species induced in liquids using atmospheric-pressure nonthermal plasma jets

    NASA Astrophysics Data System (ADS)

    Tani, Atsushi; Fukui, Satoshi; Ikawa, Satoshi; Kitano, Katsuhisa

    2015-10-01

    We investigated fatty acid oxidation by atmospheric-pressure nonthermal helium plasma using linoleic acid, an unsaturated fatty acid, together with evaluating active species induced in liquids. If the ambient gas contains oxygen, direct plasma such as plasma jets coming into contact with the liquid surface supplies various active species, such as singlet oxygen, ozone, and superoxide anion radicals, to the liquid. The direct plasma easily oxidizes linoleic acid, indicating that fatty acid oxidation will occur in the direct plasma. In contrast, afterglow flow, where the plasma is terminated in a glass tube and does not touch the surface of the liquid sample, supplies mainly superoxide anion radicals. The fact that there was no clear observation of linoleic acid oxidation using the afterglow reveals that it may not affect lipids, even in an atmosphere containing oxygen. The afterglow flow can potentially be used for the sterilization of aqueous solutions using the reduced pH method, in medical and dental applications, because it provides bactericidal activity in the aqueous solution despite containing a smaller amount of active species.

  10. The lower subsidiary diffuse plasma resonances and the classification of radio emissions below the plasma frequency

    NASA Technical Reports Server (NTRS)

    Osherovich, Vladimir A.; Benson, Robert F.

    1991-01-01

    Using previusly published data and newly scaled ionograms from the Alouette 2 and ISIS 1 experiments, the diffuse ionospheric resonances Dn, stimulated by topside sounders Dn, are classified. The classification also includes the lower subsidiary resonances Dn(-) (n = 1, 2, 3, and 4). It is shown that the Dn(-) frequencies are related to f(Dn) and f(H) by the expression f(Dn)- = sq rt of (f(Dn)-squared - f(H)-squared).

  11. Tuning the electrical property via defect engineering of single layer MoS2 by oxygen plasma

    NASA Astrophysics Data System (ADS)

    Islam, Muhammad R.; Kang, Narae; Bhanu, Udai; Paudel, Hari P.; Erementchouk, Mikhail; Tetard, Laurene; Leuenberger, Michael N.; Khondaker, Saiful I.

    2014-08-01

    We have demonstrated that the electrical property of single-layer molybdenum disulfide (MoS2) can be significantly tuned from the semiconducting to the insulating regime via controlled exposure to oxygen plasma. The mobility, on-current and resistance of single-layer MoS2 devices were varied by up to four orders of magnitude by controlling the plasma exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory studies suggest that the significant variation of electronic properties is caused by the creation of insulating MoO3-rich disordered domains in the MoS2 sheet upon oxygen plasma exposure, leading to an exponential variation of resistance and mobility as a function of plasma exposure time. The resistance variation calculated using an effective medium model is in excellent agreement with the measurements. The simple approach described here can be used for the fabrication of tunable two-dimensional nanodevices based on MoS2 and other transition metal dichalcogenides.We have demonstrated that the electrical property of single-layer molybdenum disulfide (MoS2) can be significantly tuned from the semiconducting to the insulating regime via controlled exposure to oxygen plasma. The mobility, on-current and resistance of single-layer MoS2 devices were varied by up to four orders of magnitude by controlling the plasma exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory studies suggest that the significant variation of electronic properties is caused by the creation of insulating MoO3-rich disordered domains in the MoS2 sheet upon oxygen plasma exposure, leading to an exponential variation of resistance and mobility as a function of plasma exposure time. The resistance variation calculated using an effective medium model is in excellent agreement with the measurements. The simple approach described here can be used for the fabrication of tunable two-dimensional nanodevices based on MoS2

  12. Heating of ions by high frequency electromagnetic waves in magnetized plasmas

    SciTech Connect

    Zestanakis, P. A.; Kominis, Y.; Hizanidis, K.; Ram, A. K.

    2013-07-15

    The heating of ions by high frequency electrostatic waves in magnetically confined plasmas has been a paradigm for studying nonlinear wave-particle interactions. The frequency of the waves is assumed to be much higher than the ion cyclotron frequency and the waves are taken to propagate across the magnetic field. In fusion type plasmas, electrostatic waves, like the lower hybrid wave, cannot access the core of the plasma. That is a domain for high harmonic fast waves or electron cyclotron waves—these are primarily electromagnetic waves. Previous studies on heating of ions by two or more electrostatic waves are extended to two electromagnetic waves that propagate directly across the confining magnetic field. While the ratio of the frequency of each wave to the ion cyclotron frequency is large, the frequency difference is assumed to be near the ion cyclotron frequency. The nonlinear wave-particle interaction is studied analytically using a two time-scale canonical perturbation theory. The theory elucidates the effects of various parameters on the gain in energy by the ions—parameters such as the amplitudes and polarizations of the waves, the ratio of the wave frequencies to the cyclotron frequency, the difference in the frequency of the two waves, and the wave numbers associated with the waves. For example, the ratio of the phase velocity of the envelope formed by the two waves to the phase velocity of the carrier wave is important for energization of ions. For a positive ratio, the energy range is much larger than for a negative ratio. So waves like the lower hybrid waves will impart very little energy to ions. The theoretical results are found to be in good agreement with numerical simulations of the exact dynamical equations. The analytical results are used to construct mapping equations, simplifying the derivation of the motion of ions, which are, subsequently, used to follow the evolution of an ion distribution function. The heating of ions can then be

  13. Conversion of CO2 to CO using radio-frequency atmospheric pressure plasmas

    NASA Astrophysics Data System (ADS)

    Foote, Alexander; Dedrick, James; O'Connell, Deborah; North, Michael; Gans, Timo

    2016-09-01

    Low temperature plasmas can be used for the in situ generation of CO, from relatively non-toxic CO2 . CO is very useful in many industrial chemical processes and so, via low temperature plasmas, CO2, a waste product, can be converted into a valuable chemical. The key challenges in using this method, for CO production, are optimising the energy efficiency, maximising the conversion of CO2 into CO and then separating the CO from the other species produced in the plasma. Very high yields of CO, greater than 90%, have been achieved at atmospheric pressure using argon as a carrier gas with admixtures up to 1.5% with energy efficiencies of up to 4%. The plasma generated in continuous and spatially homogeneous and is driven at a frequency of 40.68 MHz. A zero dimensional global model has also been used to simulate the chemical kinetics of the plasma to determine the dominant dissociation processes and is in good agreement with the experimentally determined yields. The model is used to determine how important a role the vibrational states of CO2 are, in a highly collisional plasma, to the production of CO and there can provide insight into how to improve the energy efficiency and suppress unwanted reactions.

  14. Plasma ionization frequency, edge-to-axis density ratio, and density on axis of a cylindrical gas discharge

    SciTech Connect

    Palacio Mizrahi, J. H.

    2014-06-15

    A rigorous derivation of expressions, starting from the governing equations, for the ionization frequency, edge-to-axis ratio of plasma density, plasma density at the axis, and radially averaged plasma density in a cylindrical gas discharge has been obtained. The derived expressions are simple and involve the relevant parameters of the discharge: Cylinder radius, axial current, and neutral gas pressure. The found expressions account for ion inertia, ion temperature, and changes in plasma ion collisionality.

  15. Absorption and emission of extraordinary-mode electromagnetic waves near cyclotron frequency in nonequilibrium plasmas

    NASA Technical Reports Server (NTRS)

    Wu, C. S.; Lin, C. S.; Wong, H. K.; Tsai, S. T.; Zhou, R. L.

    1981-01-01

    An investigation is presented of two cases: (1) weakly relativistic electrons with a loss-cone type distribution, and (2) electrons with a drift velocity parallel to the ambient magnetic field. Numerical computations are given for physical parameters close to those in the polar region of the earth magnetosphere and laboratory experiments, with attention to the fast extraordinary-mode radiation whose frequency is near that of the electron cyclotron frequency. The fast extraordinary mode can escape from a strong field region to the weaker field region and may therefore be measured outside the plasma. It is found that the X mode radiation can be amplified by means of a cyclotron maser effect when the electrons have a loss-cone distribution, and it is concluded that, when the electron energy is sufficiently high, the X mode cutoff frequency may be lower than the cyclotron frequency.

  16. Solid-Sampling Electrothermal Vaporization Inductively Coupled Plasma Optical Emission Spectrometry for Direct Determination of Total Oxygen in Coal.

    PubMed

    Vogt, Thomas; Bauer, Daniela; Nennstiel, David; Otto, Matthias

    2015-10-20

    A new analytical method for direct determination of total oxygen contents in eight coal samples of the Argonne Premium Coal (APC) series and in the NIST SRM 1632d is presented. The development of a suitable calibration procedure, optimization of measurement conditions, and the application of a tailored data processing for handling of plasma effects and high blanks enable the quantification of oxygen simultaneously with other trace, minor, or major elements in whole coal samples by means of electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP OES). For comparison, the oxygen contents were determined by a direct oxygen analyzer. The obtained oxygen values of the APC and the reference material NIST SRM 1632d were compared to data in the literature. The precision of the ETV-ICP OES was within ±3.5%, and the recovery better than 92%. With this good accuracy, the developed direct solid sampling method ETV-ICP OES is well suited for the fast determination of oxygen in coals, varying in rank from lignite to semianthracite, in a content range of about 100 ppm up to 27% using 1.5 mg sample weight. This direct analysis method represents an accurate, advantageous alternative to currently used methods for estimation of total oxygen contents in coals.

  17. Rapid assessment of singlet oxygen-induced plasma lipid oxidation and its inhibition by antioxidants with diphenyl-1-pyrenylphosphine (DPPP).

    PubMed

    Morita, Mayuko; Naito, Yuji; Yoshikawa, Toshikazu; Niki, Etsuo

    2016-01-01

    Recent studies suggesting the involvement of singlet oxygen in the pathogenesis of multiple diseases have attracted renewed attention to lipid oxidation mediated by singlet oxygen. Although the rate constants for singlet oxygen quenching by antioxidants have been measured extensively, the inhibition of lipid oxidation mediated by singlet oxygen has received relatively less attention, partly because a convenient method for measuring the rate of lipid oxidation is not available. The objective of this study was to develop a convenient method to measure plasma lipid oxidation mediated by singlet oxygen which may be applied to a rapid assessment of the antioxidant capacity to inhibit this oxidation using a conventional microplate reader. Singlet oxygen was produced from naphthalene endoperoxide, and lipid hydroperoxide production was followed by using diphenyl-1-pyrenylphosphine (DPPP). Non-fluorescent DPPP reacts stoichiometrically with lipid hydroperoxides to give highly fluorescent DPPP oxide. It was found that plasma oxidation by singlet oxygen increased the fluorescence intensity of DPPP oxide, which was suppressed by antioxidants. Fucoxanthin suppressed the oxidation more efficiently than β-carotene and α-tocopherol, while ascorbic acid and Trolox were not effective. The present method may be useful for monitoring lipid oxidation and also for rapid screening of the capacity of dietary antioxidants and natural products to inhibit lipid oxidation in a biologically relevant system.

  18. Cell attachment and biocompatibility of polytetrafluoroethylene (PTFE) treated with glow-discharge plasma of mixed ammonia and oxygen.

    PubMed

    Chen, Meng; Zamora, Paul O; Som, Prantika; Peña, Louis A; Osaki, Shigemasa

    2003-01-01

    The plasma generated from a gas mixture of NH3 plus O2 (NH3 + O2) has been used to impart unique chemical and biological characteristics to polytetrafluoroethylene (PTFE). PTFE treated with NH3 + O2 plasma was physiochemically distinct from surfaces treated with plasma of either NH3 or O2 alone, as determined by electron spectroscopy for chemical analysis (ESCA). The contact angle analysis revealed that the PTFE surfaces became less hydrophobic after plasma treatments. ESCA results indicate the presence of oxygen-containing groups and nitrogen-containing groups at the plasma-treated surfaces. PTFE treated with NH3 + O2 plasma resisted the attachment of platelets and leukocytes in a manner similar to untreated PTFE; however, the attachment of bovine aorta endothelial cells was substantially increased. Once attached, these cells grew to confluency. The increased endothelial cell attachment was higher than that observed following plasma treatment with each gas used separately, which could be attributed to the considerable amount of CF(OR)2-CF2 formed on the NH3 + O2 plasma-treated PTFE surface. At 14 days after subcutaneous implantation in rats, the PTFE wafers treated with NH3 + O2 plasma demonstrated less encapsulation and lower levels of inflammatory cells compared to controls. Collectively, the results suggest that NH3 + O2 plasma treatment imparts a unique character to PTFE and could be useful in certain in vivo applications.

  19. The surface chemistry resulting from low-pressure plasma treatment of polystyrene: The effect of residual vessel bound oxygen

    NASA Astrophysics Data System (ADS)

    Dhayal, Marshal; Alexander, Morgan R.; Bradley, James W.

    2006-09-01

    The surface chemistry of plasma treated polystyrene samples has been studied in a specially designed low-pressure argon discharge system incorporating in situ XPS analysis. By using an electrostatic grid biasing technique, the plasma source can also be used in a mode preventing ion interactions with the sample. The system, which utilizes a vacuum transfer chamber between plasma and XPS analysis has allowed us to differentiate between the level of oxygen incorporated at the polystyrene surface from residual gas during treatment and that from the exposure of the treated sample to the laboratory atmosphere. Using typical base pressures of about 5 × 10 -3 Pa (4 × 10 -5 Torr) the XPS results show that significant oxygen surface incorporation resulted from oxygen containing species in the plasma itself (i.e. water vapour with 2 × 10 -3 Pa partial pressure). The surface concentration of O was measured at 7.6 at.%. Subsequent atmospheric exposure of the treated samples resulted in only a small increase (of 0.6 at.%) in oxygen incorporation in the form of acid anhydride functionalities. XPS measurements of PS samples exposed to plasmas with no ion-surface component (i.e. exposure from VUV, UV and excited neutral species only) showed no appreciable change in oxygen incorporation compared to those with low-energy ion bombardment from the plasma (<20 eV). Given the energetics of the remaining bombarding species, it indicates that VUV radiation may be chiefly responsible for the production of free radical sites in this discharge regime.

  20. Mitigation of electron attachment to oxygen in high pressure air plasmas by vibrational excitation

    NASA Astrophysics Data System (ADS)

    Frederickson, K.; Lee, W.; Palm, P.; Adamovich, I. V.; Rich, J. W.; Lempert, W. R.

    2007-05-01

    A series of time resolved microwave attenuation measurements are performed of the electron number density of an electron beam generated, CO laser excited nonequilibrium O2/N2 plasma. Resonant absorption of infrared radiation from the CO laser produces the nonequilibrium state, in which the heavy species vibrational modes are disproportionately excited, compared to the rotational and translational modes (Tvib≈2000-3000K vs TR /T≈300K). It is shown that this results in an increase in the plasma free electron lifetime by two orders of magnitude compared to the unexcited cold gas, an effect which is ascribed to complete mitigation of rapid three-body electron attachment to molecular oxygen. A series of heavy species filtered pure rotational Raman scattering measurements are also presented, which exhibit minimal temperature change (+50K), indicating that the observed lifetime increase cannot be due to heavy-species thermal effects. Finally, computational modeling results infer an increase in the rate of O2- detachment by four to five orders of magnitude, compared to the equilibrium value.

  1. Anisotropic etching of amorphous perfluoropolymer films in oxygen-based inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Ono, Takao; Akagi, Takanori; Ichiki, Takanori

    2009-01-01

    An amorphous perfluoropolymer, "Cytop™" (Asahi Glass Co., Ltd.), is a preferable material for the fabrication of micro total analysis system devices because of its superior optical transparency over a wide wavelength range and low refractive index of 1.34, which is almost the same as that of water, as well as excellent chemical stability. To establish the precise microfabrication technology for this unique resin, the dry etching of the amorphous perfluoropolymer in Ar/O2 low-pressure inductively coupled plasma has been studied. A relatively high etch rate of approximately 6.3 μm/min at maximum and highly anisotropic etched features was attained. Plasma measurements by a single Langmuir probe technique and actinometry revealed that etching is dominated by ion-assisted surface desorption above a 10% O2 mixing ratio, whereas the supply of active oxygen species is the rate-limiting process below 10%. Moreover, angled x-ray photoelectron spectroscopy measurements of an etched trench pattern revealed that a high anisotropy is attributed to the formation of a carbon-rich sidewall protection layer.

  2. Resonant instability near the two-ion crossover frequency in the Io plasma torus

    NASA Astrophysics Data System (ADS)

    Thorne, R. M.; Moses, J. J.

    1985-07-01

    Thorne and Scarf (1984) have presented evidence for the existence of intense low-frequency fluctuating electric fields in the Io plasma torus. Two distinct mechanisms have been proposed for this phenomenon, namely, ion cyclotron instability which occurs at intermediate latitude, and whistler instability near the equator. The present investigation is concerned with a quantitative appraisal of each of these mechanisms, taking into account an evaluation of the net convective growth rate of waves along ray paths which traverse the Io torus. Aspects of wave propagation near the crossover frequency are considered along with questions regarding the resonant interaction with energetic particles.

  3. Effect of shape of scatterers and plasma frequency on the complete photonic band gap properties of two-dimensional dielectric-plasma photonic crystals

    NASA Astrophysics Data System (ADS)

    Fathollahi Khalkhali, T.; Bananej, A.

    2016-12-01

    In this study, we analyze complete photonic band gap properties of two-dimensional dielectric-plasma photonic crystals with triangular and square lattices, composed of plasma rods with different geometrical shapes in the anisotropic tellurium background. Using the finite-difference time-domain method we discuss the maximization of the complete photonic band gap width as a function of plasma frequency and plasma rods parameters with different shapes and orientations. The numerical results demonstrate that our proposed structures represent significantly wide complete photonic band gaps in comparison to previously studied dielectric-plasma photonic crystals.

  4. Plasma heating in stellarators by radio frequency electromagnetic waves at the fundamental ion cyclotron resonance

    NASA Astrophysics Data System (ADS)

    Svidzinski, Vladimir A.

    1998-11-01

    A perturbation method is developed to find the structure of Alfven wave modes in a cylindrical waveguide filled with a cold, collisional, uniform plasma with a vacuum layer between the plasma and a conducting wall when the magnetic field in the waveguide is a superposition of a uniform and an inhomogeneous /ell=2 (quadrupole) field created by helical windings. The influence of the helical field on the wave mode structure is treated as a perturbation. This innovative technique is applied in order to investigate the possibility of direct heating of plasma ions at the fundamental ion cyclotron resonance in stellarator magnetic field configuration. However, the theoretical development itself is unique and complete, and it can be useful for the analysis of other similar plasma models. We investigated the mode structure of an m=[+]1 (azimuthal wave number) fast wave which is modified by the magnetic field inhomogeneity. We found that the m=[- ]1 azimuthal component of the modified m=[+]1 fast Alfven wave is left-hand polarized in the central part of the plasma. This implies a coupling between the m=[+]1 fast (right-hand polarized) wave and m=[-]1 slow (left- hand polarized) waves due to the inhomogeneity of the /ell=2 fields. The coupling efficiency is examined for different plasma parameters. Results demonstrate that efficient coupling between the modes occurs for appropriate plasma parameters in this model, indicating that efficient plasma heating at the fundamental ion cyclotron frequency is possible in stellarators. The results of the analysis also point the way to a general theory of linear wave coupling in any inhomogeneous, anisotropic medium, since conventional mode conversion theory may be seen as just another example of this general theory.

  5. Effect of driving frequency on excitation of turbulence in a kinetic plasma

    SciTech Connect

    Parashar, T. N.; Shay, M. A.; Matthaeus, W. H.; Servidio, S.; Breech, B.

    2011-09-15

    The effect of driving frequency on the efficiency of turbulence generation through magnetic forcing is studied using kinetic hybrid simulations with fully kinetic ions and fluid electrons. The efficiency of driving is quantified by examining the energy input into magnetic field as well as the thermal energy for various driving frequencies. The driving is efficient in exciting turbulence and heating the plasma when the time period of the driving is larger than the nonlinear time of the system. For driving at faster time scales, the energy input is weak and the steady state energy is much lower. The heating of the plasma is correlated with intermittent properties of the magnetic field, which are manifested as non-Gaussian statistics. Implications for turbulence in solar corona are discussed.

  6. Investigation of Millimeter Wave Bursts at ECE Frequencies in DIII-D Plasmas

    NASA Astrophysics Data System (ADS)

    Wu, S. M.; Austin, M. E.

    2005-10-01

    Intense bursts of narrowband millimeter wave radiation have been observed in low density H-mode and QH-mode plasmas in the DIII-D tokamak. These bursts occur in the range of second harmonic electron cyclotron frequencies and have bandwidths of 1 to 4 GHz. The narrow frequency width suggests that the bursting is not classic runaway electron emission which typically has a bandwidth of 10 GHz or more. ECE bursting has been observed in three different conditions. The burst occurs simultaneously with edge-localized mode (ELM) precursors, edge harmonic oscillations, or plasma disruption precursors. In the precursor cases the bursts precede the collapse phase and are coincident with similar types of MHD events. The data will be compared to models of stimulated and scattered emission for electrons in the high energy tail of the distribution.

  7. Low-frequency, self-sustained oscillations in inductively coupled plasmas used for optical pumping

    SciTech Connect

    Coffer, J.; Encalada, N.; Huang, M.; Camparo, J.

    2014-10-28

    We have investigated very low frequency, on the order of one hertz, self-pulsing in alkali-metal inductively-coupled plasmas (i.e., rf-discharge lamps). This self-pulsing has the potential to significantly vary signal-to-noise ratios and (via the ac-Stark shift) resonant frequencies in optically pumped atomic clocks and magnetometers (e.g., the atomic clocks now flying on GPS and Galileo global navigation system satellites). The phenomenon arises from a nonlinear interaction between the atomic physics of radiation trapping and the plasma's electrical nature. To explain the effect, we have developed an evaporation/condensation theory (EC theory) of the self-pulsing phenomenon.

  8. Low-frequency, self-sustained oscillations in inductively coupled plasmas used for optical pumping

    NASA Astrophysics Data System (ADS)

    Coffer, J.; Encalada, N.; Huang, M.; Camparo, J.

    2014-10-01

    We have investigated very low frequency, on the order of one hertz, self-pulsing in alkali-metal inductively-coupled plasmas (i.e., rf-discharge lamps). This self-pulsing has the potential to significantly vary signal-to-noise ratios and (via the ac-Stark shift) resonant frequencies in optically pumped atomic clocks and magnetometers (e.g., the atomic clocks now flying on GPS and Galileo global navigation system satellites). The phenomenon arises from a nonlinear interaction between the atomic physics of radiation trapping and the plasma's electrical nature. To explain the effect, we have developed an evaporation/condensation theory (EC theory) of the self-pulsing phenomenon.

  9. Low-frequency instabilities of collisionless plasma and the 16-moment approximation

    SciTech Connect

    Dzhalilov, N. S. Kuznetsov, V. D.

    2013-12-15

    Using the 16-moment equations that take into account heat fluxes in anisotropic collisionless plasma, the properties of magnetohydrodynamic (MHD) instabilities are investigated. For all instabilities occurring in the MHD approach (the normal incompressible firehose instability, the second compressible almost longitudinal firehose instability, and the almost transverse mirror instability of slow magnetosonic modes, as well as thermal instability caused by the heat flux directed along the magnetic field), their kinetic analogs are considered. The kinetic dispersion relation in the low-frequency range in the vicinity of the ion thermal velocity is analyzed. The flow of plasma ions along the magnetic field is taken into account. The thresholds and instability growth rates obtained in the MHD and kinetic approaches are found to be in good agreement. This indicates that the 16-moment MHD equations adequately describe the dynamics of collisionless plasma.

  10. Temporally resolved ion velocity distribution measurements in a radio-frequency plasma sheath

    SciTech Connect

    Jacobs, B.; Gekelman, W.; Pribyl, P.; Barnes, M.

    2011-05-15

    The ion velocity distribution function (IVDF) above and within a radio-frequency (RF) biased plasma sheath is studied experimentally with a pulsed laser-induced fluorescence diagnostic in an industrial plasma etch tool. Temporally resolved measurements taken at eight different phases of the 2.2 MHz bias waveform show that the ion dynamics vary dramatically throughout the RF cycle (the ratio of the average ion transit time through the sheath to the RF period is {tau}{sub ion}/{tau}{sub RF} = 0.3). The position of the presheath/sheath edge is constant throughout the RF cycle and the time-averaged ion flux is conserved within the sheath region. The characteristic bimodal structure of the time-averaged ion distributions found in previous experiments is observed to arise from the time-dependent ion dynamics, in accord with existing theory. The large temporal variation of the IVDF has implications for the plasma chemistry and etching quality.

  11. Particle simulation for direct plasma injection in a radio frequency quadrupole matching section.

    PubMed

    Tamura, J; Hattori, T; Hayashizaki, N; Ishibashi, T; Kanesue, T; Kashiwagi, H; Kondo, K; Okamura, M

    2010-02-01

    We have been investigating direct plasma injection scheme (DPIS) for high-intensity heavy-ion beam acceleration. In the DPIS, laser-produced plasma is directly injected into a radio frequency quadrupole (RFQ) linac. To study the beam dynamics of the ion injection in the DPIS, we tracked particle motions in the RFQ matching section using three-dimensional particle-in-cell method. As a result of the numerical simulation, we found that the electrostatic field generated by the extraction electrode reduces the transmission efficiency. To avoid the radially defocusing force, the input beam into the RFQ has to be initially convergent. In the DPIS, further optimization of the plasma density is required for better matching.

  12. Dust removal in radio-frequency plasmas by a traveling potential modulation

    SciTech Connect

    Li Yangfang; Jiang Ke; Thomas, Hubertus M.; Morfill, Gregor E.

    2010-06-16

    The dust contamination in plasma deposition processes plays a crucial role in the quality and the yield of the products. To improve the quality and the yield of plasma processing, a favorable way is to remove the dust particles actively from the plasma reactors.Our recent experiments in the striped electrode device show that a traveling plasma modulation allows for a systematic particle removal independent of the reactor size. Besides the rf powered electrode, the striped electrode device includes a segmented electrode that consists of 100 electrically insulated narrow stripes. A traveling potential profile is produced by the modulation of the voltage signals applied on the stripes. The dust particles are trapped in the potential wells and transported with the traveling of the potential profile.The particle-in-cell (PIC) simulation on the potential above the segmented electrode indicates that the traveling potential profile can be realized either by applying low-frequency (0.1-10 Hz) voltage signals with a fixed phase shift between adjacent stripes or high-frequency (10 kHz a circumflex AS 100 MHz) signals with the amplitudes modulated by a low-frequency envelope. The transportation of the dust particles is simulated with a two-dimensional molecular dynamics (MD) code with the potential profile obtained from the PIC simulation. The MD results reproduce the experimental observations successfully.This technology allows for an active removal of the contaminating particles in processing plasmas and it is independent of the reactor size. The removal velocity is controllable by adjusting the parameters for the modulation.

  13. Tailoring Surface Properties of Polymeric Separators for Lithium-Ion Batteries by 13.56 MHz Radio-Frequency Plasma Glow Discharge

    NASA Astrophysics Data System (ADS)

    Liang, Chia-Han; Juang, Ruey-Shin; Tsai, Ching-Yuan; Huang, Chun

    2013-11-01

    The hydrophilic surface modification of the polymeric separator is achieved by low-pressure 13.56 MHz radio-frequency Ar and He gas plasma treatments. The changes in surface hydrophilicity and surface free energy were examined by static contact angle analysis. The static water contact angle of the plasma-modified polymeric separator particularly decreased with the increase in treatment time. An obvious increase in the surface energy of polymeric separators owing to the crosslinking by activated species of inert gases effect of monatomic-gas-plasma treatments was also observed. Optical emission spectroscopy was carried out to analyze the chemical species generated after Ar and He gas plasma treatments. The variations in the surface morphology and chemical structure of the polymeric separators were confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS) measurements. XPS analysis showed significantly higher surface concentrations of oxygen functional groups for monatomic-gas-plasma-modified polymeric separator surfaces than for the unmodified polymeric separator surface. The experimental results show the important role of chemical species in the interaction between Ar and He gas plasmas and the polymeric separator surface, which can be controlled by surface modification to tailor the hydrophilicity of the polymeric separator.

  14. Focused excimer laser initiated, radio frequency sustained high pressure air plasmas

    SciTech Connect

    Giar, Ryan; Scharer, John

    2011-11-15

    Measurements and analysis of air breakdown processes and plasma production by focusing 193 nm, 300 mJ, 15 MW high power laser radiation inside a 6 cm diameter helical radio frequency (RF) coil are presented. Quantum resonant multi-photon ionization (REMPI) and collisional cascade laser ionization processes are exploited that have been shown to produce high-density (n{sub e} {approx} 7 x 10{sup 16}/cm{sup 3}) cylindrical seed plasmas at 760 Torr. Air breakdown in lower pressures (from 7-22 Torr), where REMPI is the dominant laser ionization process, is investigated using an UV 18 cm focal length lens, resulting in a laser flux of 5.5 GW/cm{sup 2} at the focal spot. The focused laser power absorption and associated shock wave produce seed plasmas for sustainment by the RF (5 kW incident power, 1.5 s) pulse. Measurements of the helical RF antenna load impedance in the inductive and capacitive coupling regimes are obtained by measuring the loaded antenna reflection coefficient. A 105 GHz interferometer is used to measure the plasma electron density and collision frequency. Spectroscopic measurements of the plasma and comparison with the SPECAIR code are made to determine translational, rotational, and vibrational neutral temperatures and the associated neutral gas temperature. From this and the associated measurement of the gas pressure the electron temperature is obtained. Experiments show that the laser-formed seed plasma allows RF sustainment at higher initial air pressures (up to 22 Torr) than that obtained via RF-only initiation (<18 Torr) by means of a 0.3 J UV laser pulse.

  15. Frequency-Domain Tomography for Single-shot, Ultrafast Imaging of Evolving Laser-Plasma Accelerators

    NASA Astrophysics Data System (ADS)

    Li, Zhengyan; Zgadzaj, Rafal; Wang, Xiaoming; Downer, Michael

    2011-10-01

    Intense laser pulses propagating through plasma create plasma wakefields that often evolve significantly, e.g. by expanding and contracting. However, such dynamics are known in detail only through intensive simulations. Laboratory visualization of evolving plasma wakes in the ``bubble'' regime is important for optimizing and scaling laser-plasma accelerators. Recently snap-shots of quasi-static wakes were recorded using frequency-domain holography (FDH). To visualize the wake's evolution, we have generalized FDH to frequency-domain tomography (FDT), which uses multiple probes propagating at different angles with respect to the pump pulse. Each probe records a phase streak, imprinting a partial record of the evolution of pump-created structures. We then topographically reconstruct the full evolution from all phase streaks. To prove the concept, a prototype experiment visualizing nonlinear index evolution in glass is demonstrated. Four probes propagating at 0, 0.6, 2, 14 degrees to the index ``bubble'' are angularly and temporally multiplexed to a single spectrometer to achieve cost-effective FDT. From these four phase streaks, an FDT algorithm analogous to conventional CT yields a single-shot movie of the pump's self-focusing dynamics.

  16. REACTIVE OXYGEN SPECIES IN WHOLE BLOOD, BLOOD PLASMA AND BREAST MILK: VALIDATION OF A POTENTIAL MARKER OF EXPOSURE AND EFFECT

    EPA Science Inventory

    Reactive oxygen species (ROS) are recognized to contribute to the pathobiology of many diseases. We have applied a simple chemiluminescent (CL) probe to detect ROS in various biological fluids (plasma, whole blood, urine and breast milk) in an environmental arsenic drinking wate...

  17. Study of electron current extraction from a radio frequency plasma cathode designed as a neutralizer for ion source applications.

    PubMed

    Jahanbakhsh, Sina; Satir, Mert; Celik, Murat

    2016-02-01

    Plasma cathodes are insert free devices that are developed to be employed as electron sources in electric propulsion and ion source applications as practical alternatives to more commonly used hollow cathodes. Inductively coupled plasma cathodes, or Radio Frequency (RF) plasma cathodes, are introduced in recent years. Because of its compact geometry, and simple and efficient plasma generation, RF plasma source is considered to be suitable for plasma cathode applications. In this study, numerous RF plasma cathodes have been designed and manufactured. Experimental measurements have been conducted to study the effects of geometric and operational parameters. Experimental results of this study show that the plasma generation and electron extraction characteristics of the RF plasma cathode device strongly depend on the geometric parameters such as chamber diameter, chamber length, orifice diameter, orifice length, as well as the operational parameters such as RF power and gas mass flow rate.

  18. Study of electron current extraction from a radio frequency plasma cathode designed as a neutralizer for ion source applications

    NASA Astrophysics Data System (ADS)

    Jahanbakhsh, Sina; Satir, Mert; Celik, Murat

    2016-02-01

    Plasma cathodes are insert free devices that are developed to be employed as electron sources in electric propulsion and ion source applications as practical alternatives to more commonly used hollow cathodes. Inductively coupled plasma cathodes, or Radio Frequency (RF) plasma cathodes, are introduced in recent years. Because of its compact geometry, and simple and efficient plasma generation, RF plasma source is considered to be suitable for plasma cathode applications. In this study, numerous RF plasma cathodes have been designed and manufactured. Experimental measurements have been conducted to study the effects of geometric and operational parameters. Experimental results of this study show that the plasma generation and electron extraction characteristics of the RF plasma cathode device strongly depend on the geometric parameters such as chamber diameter, chamber length, orifice diameter, orifice length, as well as the operational parameters such as RF power and gas mass flow rate.

  19. Study of electron current extraction from a radio frequency plasma cathode designed as a neutralizer for ion source applications

    SciTech Connect

    Jahanbakhsh, Sina Satir, Mert; Celik, Murat

    2016-02-15

    Plasma cathodes are insert free devices that are developed to be employed as electron sources in electric propulsion and ion source applications as practical alternatives to more commonly used hollow cathodes. Inductively coupled plasma cathodes, or Radio Frequency (RF) plasma cathodes, are introduced in recent years. Because of its compact geometry, and simple and efficient plasma generation, RF plasma source is considered to be suitable for plasma cathode applications. In this study, numerous RF plasma cathodes have been designed and manufactured. Experimental measurements have been conducted to study the effects of geometric and operational parameters. Experimental results of this study show that the plasma generation and electron extraction characteristics of the RF plasma cathode device strongly depend on the geometric parameters such as chamber diameter, chamber length, orifice diameter, orifice length, as well as the operational parameters such as RF power and gas mass flow rate.

  20. In situ measurements of ionospheric plasma turbulence over five frequency decades: Heritage flight of the Plasma Local Anomalous Noise Experiment (PLANE)

    NASA Astrophysics Data System (ADS)

    Habash Krause, L.; Enloe, C. L.; McHarg, M. G.

    2013-12-01

    Observations of ionospheric plasma density and frequency-dependent broadband plasma turbulence made during the heritage flight of the Plasma Local Anomalous Noise Experiment (PLANE) are presented. Rather than record high frequency time series data, the experiment was designed to record Power Spectral Distributions (PSDs) in five decadal frequency bins with upper limits ranging from 1.0 Hz to 10 kHz. Additionally, PLANE was designed distinguish turbulence in the ambient plasma from that local to the spacecraft. The instrument consists of two retarding potential analyzers (RPAs) connected together via a feedback loop to force one analyzer into the I-V trace retardation region at all times. Fluctuations in this measurement are believed to be ambient only as the RPA's voltage would be too high for locally turbulent plasma to surmount the potential barrier, which is nominally at ram energy. The instrument requires pointing along the spacecraft's ram velocity vector to make this measurement, thus requiring stabilization in pitch and yaw. During PLANE's heritage flight, though the satellite's attitude control system failed early in the mission, plasma data were collected during opportune times in which the instrument rotated into and out of the ram. Observations of plasma density and PSDs of high frequency plasma turbulence were recorded on several occasions. Additionally, a plasma source onboard the satellite was used to generate artificial plasma turbulence, and the PLANE data observed periodic structure presumably associated with the rotation of the spacecraft during these source firings. A brief comparison with other high frequency in situ plasma instruments is presented.

  1. Transparent ultra water-repellent poly(ethylene terephthalate) substrates fabricated by oxygen plasma treatment and subsequent hydrophobic coating

    NASA Astrophysics Data System (ADS)

    Teshima, Katsuya; Sugimura, Hiroyuki; Inoue, Yasushi; Takai, Osamu; Takano, Atsushi

    2005-05-01

    Wettability of solid surfaces with water is well-known to be governed by chemical properties and nanotextures of the surfaces. A proper nanotexture of surfaces enhances their hydrophobicity. In this study, a novel method consisting of two dry process techniques, that is, nanotexturing by an oxygen plasma treatment and subsequent hydrophobic coating by means of low temperature chemical vapor deposition or plasma-enhanced chemical vapor deposition, was employed to form ultra water-repellent polymer sheets. A nanotexture was formed on a poly(ethylene terephthalate) substrate surface via selective oxygen plasma etching. This surface nanotexture remained after the hydrophobic coatings using organosilane precursors. The surface-modified substrate was transparent and ultra water-repellent, showing a water contact angle greater than 150°.

  2. Biodegradability of oxygen-plasma treated cellulose textile functionalized with ZnO nanoparticles as antibacterial treatment

    NASA Astrophysics Data System (ADS)

    Primc, Gregor; Tomšič, Brigita; Vesel, Alenka; Mozetič, Miran; Ercegović Ražić, Sanja; Gorjanc, Marija

    2016-08-01

    Samples of bleached cellulose fabric were treated with weakly ionized highly dissociated oxygen plasma in order to improve the binding of ZnO nanoparticles, antibacterial properties and biodegradability. Low specific discharge power of about 24 W l-1 was applied in order to minimize thermal effects following plasma treatment. Optical emission spectroscopy revealed weak etching of the fabric while x-ray photoelectron spectroscopy showed formation of oxygen-rich functional groups. Scanning electron microscopy revealed an improved uptake of ZnO nanoparticles and the standard transfer method highlighted excellent antimicrobial effects for Staphylococcus aureus and Escherichia coli. The biodegradability of all samples was determined using the standard ISO test and revealed excellent results for plasma-treated samples even in cases when they were functionalized using ZnO nanoparticles.

  3. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity.

    PubMed

    Ahmed, Shahid; Mammosser, John D

    2015-07-01

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar-O2 (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM010-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

  4. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity

    SciTech Connect

    Ahmed, Shahid; Mammosser, John D.

    2015-07-15

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar–O{sub 2} (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM{sub 010}-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

  5. Measurement of high-frequency, small scale density fluctuations in improved confinement RFP plasmas

    NASA Astrophysics Data System (ADS)

    Duff, J. R.; Chapman, B. E.; Sarff, J. S.; Carmody, D.; Terry, P. W.; den Hartog, D. J.; Morton, L. A.; Lin, L.; Ding, W. X.; Brower, D. L.; MST Team

    2014-10-01

    In standard MST RFP plasmas, core transport is governed by magnetic fluctuations associated with global tearing modes. Using pulsed parallel current drive, tearing is significantly reduced and smaller-scale fluctuations are likely important to electron particle and heat transport for these improved confinement plasmas. On MST, an 11-chord FIR laser-based interferometry diagnostic, with ~ 8 cm chord spacing, is used to measure electron density fluctuations with wavenumbers k < 1-2 cm-1. An upgrade underway will allow resolution up to k ~ 15 cm-1. A fast magnetic coil array is employed for magnetic fluctuations. High-frequency (>50 kHz) small-scale (n > 15) density and magnetic fluctuations have been observed in the edge plasma, where density and temperature gradients are largest. These fluctuations are distinct from tearing and have amplitudes that correlate with the density gradient and electron beta. The MST is well suited to explore beta scaling given the large dynamic range (9-26%) found in the device. Correlation of the measured density fluctuations with plasma parameters in high beta plasmas will serve to identify the drive and contribute to validation of gyrokinetic codes. Work supported by DOE and NSF.

  6. Creating nanoporosity in silver nanocolumns by direct exposure to radio-frequency air plasma

    NASA Astrophysics Data System (ADS)

    El Mel, Abdel-Aziz; Stephant, Nicolas; Hamon, Jonathan; Thiry, Damien; Chauvin, Adrien; Chettab, Meriem; Gautron, Eric; Konstantinidis, Stephanos; Granier, Agnès; Tessier, Pierre-Yves

    2015-12-01

    Nanoporous materials are of great importance for a broad range of applications including catalysis, optical sensors and water filtration. Although several approaches already exist for the creation of nanoporous materials, the race for the development of versatile methods, more suitable for the nanoelectronics industry, is still ongoing. In this communication we report for the first time on the possibility of generating nanoporosity in silver nanocolumns using a dry approach based on the oxidation of silver by direct exposure to a commercially available radio-frequency air plasma. The silver nanocolumns are created by glancing angle deposition using magnetron sputtering of a silver target in pure argon plasma. We show that upon exposure to the rf air plasma, the nanocolumns transform from solid silver into nanoporous silver oxide. We further show that by tuning the plasma pressure and the exposure duration, the oxidation process can be finely adjusted allowing for precisely controlling the morphology and the nanoporosity of the silver oxide nanocolumns. The generation of porosity within the silver nanocolumns is explained according to a cracking-induced oxidation mechanism based on two repeated events occurring alternately during the oxidation process: (i) oxidation of silver upon exposure to the air plasma and (ii) generation of nanocracks and blisters within the oxide layer due to the high internal stress generated within the material during oxidation.

  7. Creating nanoporosity in silver nanocolumns by direct exposure to radio-frequency air plasma.

    PubMed

    El Mel, Abdel-Aziz; Stephant, Nicolas; Hamon, Jonathan; Thiry, Damien; Chauvin, Adrien; Chettab, Meriem; Gautron, Eric; Konstantinidis, Stephanos; Granier, Agnès; Tessier, Pierre-Yves

    2016-01-07

    Nanoporous materials are of great importance for a broad range of applications including catalysis, optical sensors and water filtration. Although several approaches already exist for the creation of nanoporous materials, the race for the development of versatile methods, more suitable for the nanoelectronics industry, is still ongoing. In this communication we report for the first time on the possibility of generating nanoporosity in silver nanocolumns using a dry approach based on the oxidation of silver by direct exposure to a commercially available radio-frequency air plasma. The silver nanocolumns are created by glancing angle deposition using magnetron sputtering of a silver target in pure argon plasma. We show that upon exposure to the rf air plasma, the nanocolumns transform from solid silver into nanoporous silver oxide. We further show that by tuning the plasma pressure and the exposure duration, the oxidation process can be finely adjusted allowing for precisely controlling the morphology and the nanoporosity of the silver oxide nanocolumns. The generation of porosity within the silver nanocolumns is explained according to a cracking-induced oxidation mechanism based on two repeated events occurring alternately during the oxidation process: (i) oxidation of silver upon exposure to the air plasma and (ii) generation of nanocracks and blisters within the oxide layer due to the high internal stress generated within the material during oxidation.

  8. Effects of hyperbaric oxygen therapy combined with platelet-rich plasma on diabetic wounds: an experimental rat model

    PubMed Central

    Kahaman, Cüneyt; Kahaman, Nail; Yalçınkaya, Ulviye; Akçılar, Aydin; Akgül, Engin; Vural, Ahmet Hakan

    2016-01-01

    Introduction Hyperbaric oxygen and platelet-rich plasma are used in the treatment of diabetic wounds. The aim of this study is to evaluate the effects of hyperbaric oxygen therapy and autologous platelet concentrates in healing diabetic wounds. Material and methods Thirty-six female Wistar albino rats were used in this study. Diabetes mellitus was induced chemically with an intraperitoneal injection of streptozotocin. The rats were divided into a control group, a hyperbaric oxygen group, a platelet-rich plasma group, and a combined therapy group. Platelet-rich plasma was applied just after the creation of the wound; hyperbaric oxygen treatment was carried out daily over 7 days. Wound healing was evaluated according to four parameters: ulcerations, epidermal thickness, density of dermal collagen fibers, and proliferation of dermal blood vessels. Results The number of active ulcers in the combined therapy group was fewer than in the control group (p = 0.039), and the wound area was greatest in controls (p < 0.001). The epidermal thickness in platelet-rich plasma and combined therapy groups was non-significantly greater than in the control group (p = 0.097 and p = 0.074, respectively). The amount of fibrous collagen in these two groups was greater than in the control group (p = 0.002). Conclusions Combined hyperbaric oxygen and platelet-rich plasma therapy was found to be successful in diabetic wound healing. The combination therapy had no additive effect in terms of angiogenesis and the development of new collagen fibers. PMID:27904531

  9. Cold atmospheric-pressure air plasma treatment of C6 glioma cells: effects of reactive oxygen species in the medium produced by the plasma on cell death

    NASA Astrophysics Data System (ADS)

    Yuyang, Wang; Cheng, Cheng; Peng, Gao; Shaopeng, Li; Jie, Shen; Yan, Lan; Yongqiang, Yu; Paul, K. Chu

    2017-02-01

    An atmospheric-pressure air plasma is employed to treat C6 glioma cells in vitro. To elucidate on the mechanism causing cell death and role of reactive species (RS) in the medium produced by the plasma, the concentration of the long-lived RS such as hydrogen peroxide, nitrate, and ozone in the plasma-treated liquid (phosphate-buffered saline solution) is measured. When vitamin C is added to the medium as a ROS quencher, the viability of C6 glioma cells after the plasma treatment is different from that without vitamin C. The results demonstrate that reactive oxygen species (ROS) such as H2O2, and O3 constitute the main factors for inactivation of C6 glioma cells and the reactive nitrogen species (RNS) may only play an auxiliary role in cell death.

  10. Dispersion relations and polarizations of low-frequency waves in two-fluid plasmas

    SciTech Connect

    Zhao, Jinsong

    2015-04-15

    Analytical expressions for the dispersion relations and polarizations of low-frequency waves in magnetized plasmas based on two-fluid model are obtained. The properties of waves propagating at different angles (to the ambient magnetic field B{sub 0}) and β (the ratio of the plasma to magnetic pressures) values are investigated. It is shown that two linearly polarized waves—namely, the fast and Alfvén modes in the low-β (β≪1) plasmas, the fast and slow modes in the β∼1 plasmas, and the Alfvén and slow modes in the high-β (β≫1) plasmas—become circularly polarized at the near-parallel (to B{sub 0}) propagation. The negative magnetic-helicity of the Alfvén mode occurs only at small or moderate angles in the low-β plasmas, and the ion cross-helicity of the slow mode is nearly the same as that of the Alfvén mode in the high-β plasmas. It is also shown that the electric polarization δE{sub z}/δE{sub y} decreases with the temperature ratio T{sub e}/T{sub i} for the long-wavelength waves, and the transition between left- and right-hand polarizations of the Alfvén mode in T{sub e}/T{sub i}≠0 plasmas can disappear when T{sub e}/T{sub i}=0. The approximate dispersion relations in the near-perpendicular propagation, low-β, and high-β limits can quite accurately describe the three modes.

  11. A time-dependent model of pulse-driven radio frequency capacitively coupled collisional plasma sheath

    NASA Astrophysics Data System (ADS)

    Rahman, M. T.; Hossain, M. Mofazzal

    2017-01-01

    The time-dependent model of ion motion is used to propose an analytical model for dual frequency (DF) capacitively coupled plasma (CCP) sheath driven by a pulsed source and a radio-frequency source. In this model, the sheath is considered to be collisional. In this model, the time dependent terms of ion fluid equations are ignored, but the electric field, ion motion and ion density remain time dependent. Electron profile is assumed to be step-like. Analytical expressions for electron sheath width and sheath potential have been developed. The calculated sheath width and potential are compared with the dual radio frequency driven time dependent models of capacitively coupled plasma sheath. From the temporal evaluation of sheath motion and potential, it has been found that pulse driven sheath has higher sheath potential and sheath width than that of conventional radio frequency driven DF CCP. Moreover, it is also found that ion energy spread can be reduced using pulsed power. From the temporal investigation of sheath motion and potential, it has been found that the duty cycle of the pulse power significantly affects sheath width and sheath potential.

  12. Cyclokinetic models and simulations for high-frequency turbulence in fusion plasmas

    NASA Astrophysics Data System (ADS)

    Deng, Zhao; Waltz, R. E.; Wang, Xiaogang

    2016-10-01

    Gyrokinetics is widely applied in plasma physics. However, this framework is limited to weak turbulence levels and low drift-wave frequencies because high-frequency gyro-motion is reduced by the gyro-phase averaging. In order to test where gyrokinetics breaks down, Waltz and Zhao developed a new theory, called cyclokinetics [R. E. Waltz and Zhao Deng, Phys. Plasmas 20, 012507 (2013)]. Cyclokinetics dynamically follows the high-frequency ion gyro-motion which is nonlinearly coupled to the low-frequency drift-waves interrupting and suppressing gyro-averaging. Cyclokinetics is valid in the high-frequency (ion cyclotron frequency) regime or for high turbulence levels. The ratio of the cyclokinetic perturbed distribution function over equilibrium distribution function δf/ F can approach 1. This work presents, for the first time, a numerical simulation of nonlinear cyclokinetic theory for ions, and describes the first attempt to completely solve the ion gyro-phase motion in a nonlinear turbulence system. Simulations are performed [Zhao Deng and R. E. Waltz, Phys. Plasmas 22(5), 056101 (2015)] in a local flux-tube geometry with the parallel motion and variation suppressed by using a newly developed code named rCYCLO, which is executed in parallel by using an implicit time-advanced Eulerian (or continuum) scheme [Zhao Deng and R. E. Waltz, Comp. Phys. Comm. 195, 23 (2015)]. A novel numerical treatment of the magnetic moment velocity space derivative operator guarantee saccurate conservation of incremental entropy. By comparing the more fundamental cyclokinetic simulations with the corresponding gyrokinetic simulations, the gyrokinetics breakdown condition is quantitatively tested. Gyrokinetic transport and turbulence level recover those of cyclokinetics at high relative ion cyclotron frequencies and low turbulence levels, as required. Cyclokinetic transport and turbulence level are found to be lower than those of gyrokinetics at high turbulence levels and low- Ω* values

  13. Quantitative Determination of Density of Ground State Atomic Oxygen from Both TALIF and Emission Spectroscopy in Hot Air Plasma Generated by Microwave Resonant Cavity

    NASA Astrophysics Data System (ADS)

    Marchal, F.; Yousfi, M.; Merbahi, N.; Wattieaux, G.; Piquemal, A.

    2016-03-01

    Two experimental techniques have been used to quantify the atomic oxygen density in the case of hot air plasma generated by a microwave (MW) resonant cavity. The latter operates at a frequency of 2.45 GHz inside a cell of gas conditioning at a pressure of 600 mbar, an injected air flow of 12 L/min and an input MW power of 1 kW. The first technique is based on the standard two photon absorption laser induced fluorescence (TALIF) using xenon for calibration but applied for the first time in the present post discharge hot air plasma column having a temperature of about 4500 K near the axis of the nozzle. The second diagnostic technique is an actinometry method based on optical emission spectroscopy (OES). In this case, we compared the spectra intensities of a specific atomic oxygen line (844 nm) and the closest wavelength xenon line (823 nm). The two lines need to be collected under absolutely the same spectroscopic parameters. The xenon emission is due to the addition of a small proportion of xenon (1% Xe) of this chemically inert gas inside the air while a further small quantity of H2 (2%) is also added in the mixture in order to collect OH(A-X) and NH(A-X) spectra without noise. The latter molecular spectra are required to estimate gas and excitation temperatures. Optical emission spectroscopy measurements, at for instance the position z=12 mm on the axis plasma column that leads to a gas measured temperature equal to 3500 K, an excitation temperature of about 9500 K and an atomic oxygen density 2.09×1017±0.2×1017 cm-3. This is in very good agreement with the TALIF measurement, which is equal to 2.0×1017 cm-3.

  14. Nonlinear gyrokinetic equations for low-frequency electromagnetic waves in general plasma equilibria

    SciTech Connect

    Frieman, E.A.; Chen, L.

    1981-10-01

    A nonlinear gyrokinetic formalism for low-frequency (less than the cyclotron frequency) microscopic electromagnetic perturbations in general magnetic field configurations is developed. The nonlinear equations thus derived are valid in the strong-turbulence regime and contain effects due to finite Larmor radius, plasma inhomogeneities, and magentic field geometries. The specific case of axisymmetric tokamaks is then considered, and a model nonlinear equation is derived for electrostatic drift waves. Also, applying the formalism to the shear Alfven wave heating sceme, it is found that nonlinear ion Landau damping of kinetic shear-Alfven waves is modified, both qualitatively and quantitatively, by the diamagnetic drift effects. In particular, wave energy is found to cascade in wavenumber instead of frequency.

  15. Modeling Plasma Formation in a Micro-gap at Microwave Frequency

    NASA Astrophysics Data System (ADS)

    Bowman, Arthur; Remillard, Stephen

    2013-03-01

    In the presence of a strong electric field, gas molecules become ionized, forming a plasma. The study of this dielectric breakdown at microwave frequency has important applications in improving the operation of radio frequency (RF) devices, where the high electric fields present in small gaps can easily ionize gases like air. A cone and tuner resonant structure was used to induce breakdown of diatomic Nitrogen in adjustable micro-gaps ranging from 13 to 1,156 μm. The electric field for plasma formation exhibited strong pressure dependence in the larger gap sizes, as predicted by previous theoretical and experimental work. Pressure is proportional to the frequency of collision between electrons and molecules, which increases with pressure when the gap is large, but levels off in the micro-gap region. A separate model of the breakdown electric field based on the characteristic diffusion length of the plasma also fit the data poorly for these smaller gap sizes. This may be explained by a hypothesis that dielectric breakdown at and below the 100 μm gap size occurs outside the gap, an argument that is supported by the observation of very high breakdown threshold electric fields in this region. Optical emissions revealed that vibrational and rotational molecular transitions of the first positive electronic system are suppressed in micro-gaps, indicating that transitions into the molecular ground state do not occur in micro-gap plasmas. Acknowledgements: National Science Foundation under NSF-REU Grant No. PHY/DMR-1004811, the Provost's Office of Hope College, and the Hope College Division of Natural and Applied Sciences.

  16. Impact of interstitial oxygen trapped in silicon during plasma growth of silicon oxy-nitride films for silicon solar cell passivation

    NASA Astrophysics Data System (ADS)

    Saseendran, Sandeep S.; Saravanan, S.; Raval, Mehul C.; Kottantharayil, Anil

    2016-03-01

    Low temperature oxidation of silicon in plasma ambient is a potential candidate for replacing thermally grown SiO2 films for surface passivation of crystalline silicon solar cells. In this work, we report the growth of silicon oxy-nitride (SiOxNy) film in N2O plasma ambient at 380 °C. However, this process results in trapping of interstitial oxygen within silicon. The impact of this trapped interstitial oxygen on the surface passivation quality is investigated. The interstitial oxygen trapped in silicon was seen to decrease for larger SiOxNy film thickness. Effective minority carrier lifetime (τeff) measurements on n-type float zone silicon wafers passivated by SiOxNy/silicon nitride (SiNv:H) stack showed a decrease in τeff from 347 μs to 68 μs, for larger SiOxNy film thickness due to degradation in interface properties. From high frequency capacitance-voltage measurements, it was concluded that the surface passivation quality was governed by the interface parameters (fixed charge density and interface state density). High temperature firing of the SiOxNy/SiNv:H stack resulted in a severe degradation in τeff due to migration of oxygen across the interface into silicon. However, on using the SiOxNy/SiNv:H stack for emitter surface passivation in screen printed p-type Si solar cells, an improvement in short wavelength response was observed in comparison to the passivation by SiNv:H alone, indicating an improvement in emitter surface passivation quality.

  17. Plasma osmolality and oxygen consumption of perch Perca fluviatilis in response to different salinities and temperatures.

    PubMed

    Christensen, E A F; Svendsen, M B S; Steffensen, J F

    2017-03-01

    The present study determined the blood plasma osmolality and oxygen consumption of the perch Perca fluviatilis at different salinities (0, 10 and 15) and temperatures (5, 10 and 20° C). Blood plasma osmolality increased with salinity at all temperatures. Standard metabolic rate (SMR) increased with salinity at 10 and 20° C. Maximum metabolic rate (MMR) and aerobic scope was lowest at salinity of 15 at 5° C, yet at 20° C, they were lowest at a salinity of 0. A cost of osmoregulation (SMR at a salinity of 0 and 15 compared with SMR at a salinity of 10) could only be detected at a salinity of 15 at 20° C, where it was 28%. The results show that P. fluviatilis have capacity to osmoregulate in hyper-osmotic environments. This contradicts previous studies and indicates intraspecific variability in osmoregulatory capabilities among P. fluviatilis populations or habitat origins. An apparent cost of osmoregulation (28%) at a salinity of 15 at 20° C indicates that the cost of osmoregulation in P. fluviatilis increases with temperature under hyperosmotic conditions and a power analysis showed that the cost of osmoregulation could be lower than 12·5% under other environmental conditions. The effect of salinity on MMR is possibly due to a reduction in gill permeability, initiated to reduce osmotic stress. An interaction between salinity and temperature on aerobic scope shows that high salinity habitats are energetically beneficial during warm periods (summer), whereas low salinity habitats are energetically beneficial during cold periods (winter). It is suggested, therefore, that the seasonal migrations of P. fluviatilis between brackish and fresh water is to select an environment that is optimal for metabolism and aerobic scope.

  18. Centaur feedline dynamics study using power spectral methods. [fundamental mode resonant frequencies of RL-10 oxygen and hydrogen feed lines

    NASA Technical Reports Server (NTRS)

    Lorenzo, C. F.

    1974-01-01

    Tests were conducted to determine the dynamic characteristics of the Centaur/RL-10 oxygen and hydrogen feedlines. The fundamental-mode resonant frequencies were determined by applying power spectral methods to noise-generated data from hot firings of the RL-10 engine. The effect of net positive suction pressure of the main feed pumps on resonant frequency characteristics was determined to be a straight-line relation. Power spectral methods were also used to determine the dynamic characteristics of the boost pumps.

  19. Experiments with Plasmas Produced by Potassium-Seeded Cyanogen Oxygen Flames for Study of Radio Transmission at Simulated Reentry Vehicle Plasma Conditions

    NASA Technical Reports Server (NTRS)

    Huber, Paul W.; Gooderum, Paul B.

    1961-01-01

    A method for the chemical production of an ionized gas stream for application to radio transmission studies is described. Involved is the combustion of gaseous cyanogen and oxygen with the addition of vaporized potassium in some cases to further increase the ionization. Experiments are described in which a 3-inch-diameter subsonic free jet at atmospheric pressure is used, and the results are presented. The plasma obtained by using this method is sufficient to simulate plasma conditions expected for reentering hypersonic vehicles. The unseeded plasma stream temperature is indicated to be about 4,200 K, with the degree of ionization indicated to be that expected from thermal equilibrium considerations. Measurements of radio-signal loss due to the unseeded flame plasma are presented for microwaves of 8 to 20 kmc transmitted through the stream and for a dipole transmitting model of 219.5 mc immersed in the stream. Favorable comparison of these results with the simple plane-wave signal-attenuation theory was obtained. In the case of a 9.4-kmc microwave signal of 30-kw peak power, the preliminary indication is that the plasma characteristics were not changed due to this strong signal. Comparison of a simplified concept of radio-signal attenuation due to plasmas is made with some hypersonic reentry vehicle signal-loss data. Other areas of plasma research using this method for the transmission problem are indicated.

  20. Effect of oxygen plasma treatment on the electrical characteristics of Pt/n-type Si Schottky diodes

    NASA Astrophysics Data System (ADS)

    Janardhanam, V.; Jyothi, I.; Yuk, Shim-Hoon; Choi, Chel-Jong; Lee, Sung-Nam; Reddy, V. Rajagopal

    2016-10-01

    The electrical properties of Pt/n-type Si Schottky diodes fabricated from n-type Si wafers subjected to an oxygen (O2) plasma treatment were investigated as a function of the power of the O2 plasma. The Pt/n-type Si Schottky diode with an O2 plasma treatment at a power of 100 W showed better rectifying characteristics with increasing barrier height and decreasing ideality factor compared to the conventional Pt/n-type Si Schottky diodes. This could be attributed to an improvement in the interface homogeneity associated with damage-free surface smoothing driven by the O2 plasma treatment at a power of 100 W. On the other hand, with increasing power of the O2 plasma for powers above 150 W, the barrier height decreased and the leakage current increased, indicating degradation of the device performance. The degradation in the rectifying properties after the O2 plasma treatment at a higher plasma power in excess of 150 W could be associated with increases in the series resistance and the interface state density caused by plasma-induced damage to the Si surface.

  1. Detonation mode and frequency analysis under high loss conditions for stoichiometric propane-oxygen

    DOE PAGES

    Jackson, Scott I.; Lee, Bok Jik; Shepherd, Joseph E.

    2016-03-24

    In this paper, the propagation characteristics of galloping detonations were quantified with a high-time-resolution velocity diagnostic. Combustion waves were initiated in 30-m lengths of 4.1-mm inner diameter transparent tubing filled with stoichiometric propane–oxygen mixtures. Chemiluminescence from the resulting waves was imaged to determine the luminous wave front position and velocity every 83.3 μ. As the mixture initial pressure was decreased from 20 to 7 kPa, the wave was observed to become increasingly unsteady and transition from steady detonation to a galloping detonation. While wave velocities averaged over the full tube length smoothly decreased with initial pressure down to half ofmore » the Chapman–Jouguet detonation velocity (DCJ) at the quenching limit, the actual propagation mechanism was seen to be a galloping wave with a cycle period of approximately 1.0 ms, corresponding to a cycle length of 1.3–2.0 m or 317–488 tube diameters depending on the average wave speed. The long test section length of 7300 tube diameters allowed observation of up to 20 galloping cycles, allowing for statistical analysis of the wave dynamics. In the galloping regime, a bimodal velocity distribution was observed with peaks centered near 0.4 DCJ and 0.95 DCJ. Decreasing initial pressure increasingly favored the low velocity mode. Galloping frequencies ranged from 0.8 to 1.0 kHz and were insensitive to initial mixture pressure. Wave deflagration-to-detonation transition and detonation failure trajectories were found to be repeatable in a given test and also across different initial mixture pressures. The temporal duration of wave dwell at the low and high velocity modes during galloping was also quantified. It was found that the mean wave dwell duration in the low velocity mode was a weak function of initial mixture pressure, while the mean dwell time in the high velocity mode depended exponentially on initial mixture pressure. Analysis of the velocity

  2. Detonation mode and frequency analysis under high loss conditions for stoichiometric propane-oxygen

    SciTech Connect

    Jackson, Scott I.; Lee, Bok Jik; Shepherd, Joseph E.

    2016-03-24

    In this paper, the propagation characteristics of galloping detonations were quantified with a high-time-resolution velocity diagnostic. Combustion waves were initiated in 30-m lengths of 4.1-mm inner diameter transparent tubing filled with stoichiometric propane–oxygen mixtures. Chemiluminescence from the resulting waves was imaged to determine the luminous wave front position and velocity every 83.3 μ. As the mixture initial pressure was decreased from 20 to 7 kPa, the wave was observed to become increasingly unsteady and transition from steady detonation to a galloping detonation. While wave velocities averaged over the full tube length smoothly decreased with initial pressure down to half of the Chapman–Jouguet detonation velocity (DCJ) at the quenching limit, the actual propagation mechanism was seen to be a galloping wave with a cycle period of approximately 1.0 ms, corresponding to a cycle length of 1.3–2.0 m or 317–488 tube diameters depending on the average wave speed. The long test section length of 7300 tube diameters allowed observation of up to 20 galloping cycles, allowing for statistical analysis of the wave dynamics. In the galloping regime, a bimodal velocity distribution was observed with peaks centered near 0.4 DCJ and 0.95 DCJ. Decreasing initial pressure increasingly favored the low velocity mode. Galloping frequencies ranged from 0.8 to 1.0 kHz and were insensitive to initial mixture pressure. Wave deflagration-to-detonation transition and detonation failure trajectories were found to be repeatable in a given test and also across different initial mixture pressures. The temporal duration of wave dwell at the low and high velocity modes during galloping was also quantified. It was found that the mean wave dwell duration in the low velocity mode was a weak function of initial mixture pressure, while the mean dwell time in the high velocity mode depended exponentially on initial mixture pressure. Analysis

  3. Broadband frequency ECR ion source concepts with large resonant plasma volumes

    SciTech Connect

    Alton, G.D.

    1995-12-31

    New techniques are proposed for enhancing the performances of ECR ion sources. The techniques are based on the use of high-power, variable-frequency, multiple-discrete-frequency, or broadband microwave radiation, derived from standard TWT technology, to effect large resonant ``volume`` ECR sources. The creation of a large ECR plasma ``volume`` permits coupling of more power into the plasma, resulting in the heating of a much larger electron population to higher energies, the effect of which is to produce higher charge state distributions and much higher intensities within a particular charge state than possible in present forms of the ECR ion source. If successful, these developments could significantly impact future accelerator designs and accelerator-based, heavy-ion-research programs by providing multiply-charged ion beams with the energies and intensities required for nuclear physics research from existing ECR ion sources. The methods described in this article can be used to retrofit any ECR ion source predicated on B-minimum plasma confinement techniques.

  4. Theory of high-frequency waves in a coaxial plasma wave guide

    NASA Astrophysics Data System (ADS)

    Maraghechi, B.; Farrokhi, B.; Willett, J. E.

    1999-10-01

    An analysis of the high-frequency eigenmodes of a coaxial wave guide containing a magnetized annular plasma column is presented. A transcendental equation is derived from the boundary conditions in the form of an eighth-order determinant equated to zero. Simultaneous solution of this determinantal equation and a polynomial equation derived from the wave equation yields the dispersion relations for the eigenmodes. By reduction of the order of the determinant the appropriate transcendental equation is easily obtained for some special cases, e.g., partially filled coaxial wave guide. The electrostatic treatment of a coaxial cylindrical wave guide is also presented. The corresponding transcendental equation is reduced to some special cases, e.g., conventional wave guide containing an annular plasma column under electrostatic approximation. Numerical solutions are obtained for some azimuthally symmetric EH (perturbed TM) and HE (perturbed TE) wave guide modes, cyclotron modes, and space-charge modes. A strong dependence of the frequencies of these electromagnetic-electrostatic waves on the radii of the coaxial wave guide and the plasma column is revealed.

  5. Effect of an oxygen plasma on the physical and chemical properties of several fluids for the liquid droplet radiator

    NASA Technical Reports Server (NTRS)

    Gulino, D. A.; Coles, C. E.

    1986-01-01

    The Liquid Droplet Radiator is one of several radiator systems currently under investigation by NASA Lewis Research Center. It involves the direct exposure of the radiator working fluid to the space environment. An area of concern is the potential harmful effects of the low-Earth-orbit atomic oxygen environment on the radiator working fluid. To address this issue, seven candidate fluids were exposed to an oxygen plasma environment in a laboratory plasma asher. The fluids studied included Dow Corning 705 Diffusion Pump Fluid, polymethylphenylsiloxane and polydimethlsiloxane, both of which are experimental fluids made by Dow Corning, Fomblin Z25, made by Montedison, and three fluids from the Krytox family of fluids, Krytox 143AB, 1502, and 16256, which are made by DuPont. The fluids were characterized by noting changes in visual appearance, physical state, mass, and infrared spectra. Of the fluids tested, the Fomblin and the three Krytoxes were the least affected by the oxygen plasma. The only effect noted was a change in mass, which was most likely due to an oxygen-catalyzed deploymerization of the fluid molecule.

  6. Effect of an oxygen plasma on the physical and chemical properties of several fluids for the Liquid Droplet Radiator

    NASA Technical Reports Server (NTRS)

    Gulino, Daniel A.; Coles, Carolyn E.

    1987-01-01

    The Liquid Droplet Radiator is one of several radiator systems currently under investigation by NASA Lewis Research Center. It involves the direct exposure of the radiator working fluid to the space environment. An area of concern is the potential harmful effects of the low-Earth-orbit atomic oxygen environment on the radiator working fluid. To address this issue, seven candidate fluids were exposed to an oxygen plasma environment in a laboratory plasma asher. The fluids studied included Dow Corning 705 Diffusion Pump Fluid, polymethylphenylsiloxane and polydimethylsiloxane, both of which are experimental fluids made by Dow Corning, Fomblin Z25, made by Montedison, and three fluids from the Krytox family of fluids, Krytox 143AB, 1502, and 16256, which are made by DuPont. The fluids were characterized by noting changes in visual appearance, physical state, mass, and infrared spectra. Of the fluids tested, the Fomblin and the three Krytoxes were the least affected by the oxygen plasma. The only effect noted was a change in mass, which was most likely due to an oxygen-catalyzed depolymerization of the fluid molecule.

  7. Radio frequency plasma power dependence of the moisture permeation barrier characteristics of Al{sub 2}O{sub 3} films deposited by remote plasma atomic layer deposition

    SciTech Connect

    Jung, Hyunsoo; Choi, Hagyoung; Lee, Sanghun; Jeon, Heeyoung; Jeon, Hyeongtag

    2013-11-07

    In the present study, we investigated the gas and moisture permeation barrier properties of Al{sub 2}O{sub 3} films deposited on polyethersulfone films (PES) by capacitively coupled plasma (CCP) type Remote Plasma Atomic Layer Deposition (RPALD) at Radio Frequency (RF) plasma powers ranging from 100 W to 400 W in 100 W increments using Trimethylaluminum [TMA, Al(CH{sub 3}){sub 3}] as the Al source and O{sub 2} plasma as the reactant. To study the gas and moisture permeation barrier properties of 100-nm-thick Al{sub 2}O{sub 3} at various plasma powers, the Water Vapor Transmission Rate (WVTR) was measured using an electrical Ca degradation test. WVTR decreased as plasma power increased with WVTR values for 400 W and 100 W of 2.6 × 10{sup −4} gm{sup −2}day{sup −1} and 1.2 × 10{sup −3} gm{sup −2}day{sup −1}, respectively. The trends for life time, Al-O and O-H bond, density, and stoichiometry were similar to that of WVTR with improvement associated with increasing plasma power. Further, among plasma power ranging from 100 W to 400 W, the highest power of 400 W resulted in the best moisture permeation barrier properties. This result was attributed to differences in volume and amount of ion and radical fluxes, to join the ALD process, generated by O{sub 2} plasma as the plasma power changed during ALD process, which was determined using a plasma diagnosis technique called the Floating Harmonic Method (FHM). Plasma diagnosis by FHM revealed an increase in ion flux with increasing plasma power. With respect to the ALD process, our results indicated that higher plasma power generated increased ion and radical flux compared with lower plasma power. Thus, a higher plasma power provides the best gas and moisture permeation barrier properties.

  8. Numerical Simulation of Waves Driven by Plasma Currents Generated by Low-Frequency Alfven Waves in a Multi-Ion Plasma

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Khazanov, George

    2003-01-01

    When multi-ion plasma consisting of heavy and light ions is permeated by a lowfrequency Alfien (LFA) wave, the EXB and the polarization drifts of the different ion species and the electrons could be quite different. The relative drifts between the charged-particle species drive waves, which energize the plasma. Using 2.5-D particle-in-cell simulations, we study this process of wave generation and its nonlinear consequences in terms of acceleration and heating plasma. Specifically we study the situation for LFA wave frequency being lower than the heavyion cyclotron frequency in a multi-ion plasma. We impose such a wave to the plasma assuming that its wavelength is much larger than that of the waves generated by the relative drifts. For better understanding, the LFA-wave driven simulations are augmented by those driven by initialized ion beams.

  9. Investigation of Atomic Oxygen Erosion of Polyimide Kapton H Exposed to a Plasma Asher Environment

    NASA Technical Reports Server (NTRS)

    Snyder, Aaron

    1999-01-01

    Experimental results are presented on the erosion characteristics of the polyimide Kapton H, which serves as a blanket material in solar arrays. This polymer has a number of characteristics that make it a suitable choice for both terrestrial and space applications. In this paper attention is focused on the durability of protected Kapton when exposed to atomic oxygen (AO) in a plasma asher. A strip of 0.025-mm thick Kapton film, coated on both sides with SiO2, was studied during a 1306 hour exposure. The erosion, located at defect sites in the protective coating and measured optically, is described in terms of volume loss as a function of AO fluence. Three simple geometric profiles are used to generate a useful array of cavity shapes to model erosion evolution. These models connect the volume erosion rate to the observed lateral expansion of the developing cavities via their diameters, measured adviacent to the upper and lower protective film, and fitted by least-squares regression to simple power law functions of fluence. The rationale for the choice of models is discussed. It was found that lateral growth in cavity size evolves less than linearly with fluence.

  10. HEMORHEOLOGICAL IMPLICATIONS OF PERFLUOROCARBON BASED OXYGEN CARRIER INTERACTION WITH COLLOID PLASMA EXPANDERS AND BLOOD

    PubMed Central

    Vásquez, Diana M.; Ortiz, Daniel; Alvarez, Oscar A.; Briceño, Juan C.; Cabrales, Pedro

    2013-01-01

    Perfluorocarbon (PFC) emulsion based oxygen carriers lack colloid osmotic pressure (COP) and must be administered with colloid-based plasma expanders (PEs). Although PFC emulsions have been widely studied, there is limited information about PFC emulsion interaction with PEs and blood. Their interaction forms aggregates due to electrostatic and rheological phenomena, and change blood rheology and blood flow. This study analyzes the effects of the interaction between PFC emulsions with blood in the presence of clinically-used PEs. The rheological behavior of the mixtures was analyzed in parallel with in vivo analysis of blood flow in microvessels using intravital microscopy when administered in a clinically relevant scenario. The interaction between the PFC emulsion and PE with blood produced PFC droplets and red blood cell (RBCs) aggregation, and increased blood viscosity. The PFC droplets formed aggregates when mixed with PEs containing electrolytes, and the aggregation increased with the electrolyte concentration. Mixtures of PFC with PEs that produced PFC aggregates also induced RCBs aggregation when mixed with blood, increasing blood viscosity at low shear rates. The more viscous suspension at low shear rates produced a blunted blood flow velocity profile in vivo relative to non-aggregating mixtures of PFC and PEs. For the PEs evaluated, albumin produced minimal to undetectable aggregation. PFC and PEs interaction with blood can affect sections of the microcirculation with low shear rate (e.g. arterioles, venules, and pulmonary circulation) because aggregates could cause capillary occlusion, decrease perfusion, pulmonary emboli, or focal ischemia. PMID:23606592

  11. Oxygen bomb combustion of biological samples for inductively coupled plasma optical emission spectrometry

    NASA Astrophysics Data System (ADS)

    Souza, Gilberto B.; Carrilho, Elma Neide V. M.; Oliveira, Camila V.; Nogueira, Ana Rita A.; Nóbrega, Joaquim A.

    2002-12-01

    A rapid sample preparation method is proposed for decomposition of milk powder, corn bran, bovine and fish tissues, containing certified contents of the analytes. The procedure involves sample combustion in a commercial stainless steel oxygen bomb operating at 25 bar. Most of the samples were decomposed within 5 min. Diluted nitric acid or water-soluble tertiary amines 10% v/v were used as absorption solutions. Calcium, Cu, K, Mg, Na, P, S and Zn were recovered with the bomb washings and determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Ethanol mixed with paraffin was used as a combustion aid to allow complete combustion. A cooling step prior releasing of the bomb valve was employed to increase the efficiency of sample combustion. Iodine was also determined in milk samples spiked with potassium iodide to evaluate the volatilization and collection of iodine in amine CFA-C medium and the feasibility of its determination by ICP-OES with axial view configuration. Most of the element recoveries in the samples were between 91 and 105% and the certified and found contents exhibited a fair agreement at a 95% confidence level.

  12. Metal-insulator transition at lanthanum aluminate-strontium titanate interface induced by oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Dai, Weitao; Cen, Cheng

    The formation of two-dimensional electron gas (2DEG) at lanthanum aluminate (LAO)-strontium titanate (STO) interface, as well as the 2DEG's unique characters in metal-insulator transition, have evoked widespread interest. Highly insulating interfaces are obtained for the structures with LAO thickness below 3 unit cell (uc) and abrupt transition from an insulating to conducting interface was observed for samples with thicker LAO layers. For 3uc LAO/STO samples, reversible nanoscale control of the metal-insulator transition was implemented by a conductive AFM writing. Our research furtherly discovered a very stable metal-insulator transition can be achieved by oxygen plasma (OP) treatment for samples with thicker LAO layers. AFM imaging and XPS measurement demonstrated the low energy OP treatment altered only the surface bonds, which confirmed the importance of surface properties in the heterostructures. Then microscale Hall bars were patterned at the interface and imaged by electrostatic force microscope. Their transport and magnetic properties were measured. This research will promote deeper understanding about the interfacial metal-insulator transition mechanism and open new device opportunities. This work is supported by the Department of Energy Grant No. DE-SC-0010399 and National Science Foundation Grant No. NSF-1454950.

  13. High and low frequency instabilities driven by counter-streaming electron beams in space plasmas

    SciTech Connect

    Mbuli, L. N.; Maharaj, S. K.; Bharuthram, R.

    2014-05-15

    A four-component plasma composed of a drifting (parallel to ambient magnetic field) population of warm electrons, drifting (anti-parallel to ambient magnetic field) cool electrons, stationary hot electrons, and thermal ions is studied in an attempt to further our understanding of the excitation mechanisms of broadband electrostatic noise (BEN) in the Earth's magnetospheric regions such as the magnetosheath, plasmasphere, and plasma sheet boundary layer (PSBL). Using kinetic theory, beam-driven electrostatic instabilities such as the ion-acoustic, electron-acoustic instabilities are found to be supported in our multi-component model. The dependence of the instability growth rates and real frequencies on various plasma parameters such as beam speed, number density, temperature, and temperature anisotropy of the counter-streaming (relative to ambient magnetic field) cool electron beam are investigated. It is found that the number density of the anti-field aligned cool electron beam and drift speed play a central role in determining which instability is excited. Using plasma parameters which are closely correlated with the measurements made by the Cluster satellites in the PSBL region, we find that the electron-acoustic and ion-acoustic instabilities could account for the generation of BEN in this region.

  14. Kinetic theory of low-frequency cross-field instability in a weakly ionized plasma. I

    SciTech Connect

    Dimant, Y.S.; Sudan, R.N.

    1995-04-01

    A consistent kinetic theory is developed for the description of electrons under conditions of a low-frequency two-stream {bold E}{times}{bold B} instability in collisionally dominated, weakly ionized plasmas. Starting from the Boltzmann collision integral, a simplified kinetic equation for the electron distribution function has been derived, which takes into account strong pitch-angle scattering of electrons by neutrals, velocity dependence of the electron--neutral collision frequency, etc. Linearized equations describing small oscillations of the electron distribution function and ion density are presented. For the asymptotic case of short waves, the dispersion relation of the {bold E}{times}{bold B} instability has been obtained and analyzed under conditions typical for the lower ionosphere. Under certain conditions, the rigorous kinetic consideration yields substantial changes in results compared to previous theories. The general approach may be applied to other linear and nonlinear low-frequency processes in a weakly ionized plasma. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  15. Plasma characteristics of argon glow discharge produced by AC power supply operating at low frequencies

    NASA Astrophysics Data System (ADS)

    Kongpiboolkid, Watcharapon; Mongkolnavin, Rattachat

    2015-04-01

    Non-thermal properties of Argon glow discharge operating with various operating pressures were measured and presented in this work. The Argon plasma is produced by a parallel conducting electrodes coupling with a high voltage AC power supply. The power supply can generate high AC voltage at various frequencies. The frequencies for the operation are in the range of a few kHz. The system is capable of generating electric field between the two metal electrodes discharge system. The characteristics of plasma produced were measured by optical emission spectroscopy (OES) technique where electron temperature (Te) and electron number density (ne) can be determined by line intensity ratio method. The value of electron number density was then determined from the Saha-Eggert equation. Our results show that the electron number density of the discharge obtained is of the order of 10-17 - 10-18 m-3 where the electron temperature is between 1.00-2.00 eV for various operating frequencies used which are in good agreement with similar results published earlier.

  16. Plasma characteristics of argon glow discharge produced by AC power supply operating at low frequencies

    SciTech Connect

    Kongpiboolkid, Watcharapon; Mongkolnavin, Rattachat

    2015-04-24

    Non-thermal properties of Argon glow discharge operating with various operating pressures were measured and presented in this work. The Argon plasma is produced by a parallel conducting electrodes coupling with a high voltage AC power supply. The power supply can generate high AC voltage at various frequencies. The frequencies for the operation are in the range of a few kHz. The system is capable of generating electric field between the two metal electrodes discharge system. The characteristics of plasma produced were measured by optical emission spectroscopy (OES) technique where electron temperature (T{sub e}) and electron number density (n{sub e}) can be determined by line intensity ratio method. The value of electron number density was then determined from the Saha-Eggert equation. Our results show that the electron number density of the discharge obtained is of the order of 10{sup −17} − 10{sup −18} m{sup −3} where the electron temperature is between 1.00−2.00 eV for various operating frequencies used which are in good agreement with similar results published earlier.

  17. A dominant role of oxygen additive on cold atmospheric-pressure He + O{sub 2} plasmas

    SciTech Connect

    Yang, Aijun; Liu, Dingxin E-mail: xhw@mail.xjtu.edu.cn; Rong, Mingzhe; Wang, Xiaohua E-mail: xhw@mail.xjtu.edu.cn; Kong, Michael G.

    2014-08-15

    We present in this paper how oxygen additive impacts on the cold atmospheric-pressure helium plasmas by means of a one-dimensional fluid model. For the oxygen concentration [O{sub 2}] > ∼0.1%, the influence of oxygen on the electron characteristics and the power dissipation becomes important, e.g., the electron density, the electron temperature in sheath, the electron-coupling power, and the sheath width decreasing by 1.6 to 16 folds with a two-log increase in [O{sub 2}] from 0.1% to 10%. Also the discharge mode evolves from the γ mode to the α mode. The reactive oxygen species are found to peak in the narrow range of [O{sub 2}] = 0.4%–0.9% in the plasmas, similar to their power-coupling values. This applies to their wall fluxes except for those of O* and O{sub 2}{sup −}. These two species have very short lifetimes, thus only when generated in boundary layers within several micrometers next to the electrode can contribute to the fluxes. The dominant reactive oxygen species and the corresponding main reactions are schematically presented, and their relations are quantified for selected applications.

  18. Narrow band wave emissions and noise around the plasma frequency in the solar wind

    NASA Astrophysics Data System (ADS)

    Chugunov, Yu. V.; Hayosh, M.; Fiala, V.; Soucek, J.; Santolik, O.; Pickett, J.

    2007-08-01

    The wave data obtained with a wide band instrument were recently used for interpretation of both quasi-thermal noise spectra and narrow band signals observed in the near vicinity of the local plasma frequency on CLUSTER II spacecraft in the solar wind, well upstream of the Earth's bow shock [1, 2] This approach is planned to continue with the large Cluster database and will be of use for other space missions such as Stereo and Solar Orbiter. If available, multi-component and/or multi-point measurements are expected to provide even greater insight in the generation of radio waves in the heliosphere in this frequency range. Our approach is based on a novel study of performance of receiving antennas in resonance regions in a streaming plasma. As far as noise spectra is concerned two distinctive features appear: a cutoff shifted down below the plasma frequency by a factor proportional to the ratio of stream velocity to the electron thermal velocity squared. The spectral maximum depends on the orientation of the antenna axis with respect to the stream velocity; it is shifted above the plasma frequency according to the antenna orientation, which is changing with the spacecraft spin. When the time resolution of the instrument is sufficient, it is possible to follow these changes. The overall form of the spectrum depends on the plasma distribution function, but even with a simplified model of two electron populations with largely different temperatures the estimates of the drift velocity and/or the temperature of the hot component can be obtained. In the case of a quasi-harmonic wave (narrow band signal) incident on the antenna, it is the antenna's effective length that allows for conversion of the open circuit voltage induced on its terminals to the electric field of the incoming wave. We show that this effective length grows by more than an order of magnitude under resonance conditions. This was already confirmed for waves propagating close to the lower oblique resonance

  19. Observation of quasi-periodic frequency sweeping in electron cyclotron emission of nonequilibrium mirror-confined plasma

    NASA Astrophysics Data System (ADS)

    Viktorov, M. E.; Shalashov, A. G.; Mansfeld, D. A.; Golubev, S. V.

    2016-12-01

    Chirping frequency patterns have been observed in the electron cyclotron emission from strongly nonequilibrium plasma confined in a table-top mirror magnetic trap. Such patterns are typical for the formation of nonlinear phase-space structures in a proximity of the wave-particle resonances of a kinetically unstable plasma, also known as the “holes and clumps” mechanism. Our data provides the first experimental evidence for the acting of this mechanism in the electron cyclotron frequency domain.

  20. Nonlinear frequency shift of electrostatic waves in general collisionless plasma: Unifying theory of fluid and kinetic nonlinearities

    SciTech Connect

    Liu, Chang; Dodin, Ilya Y.

    2015-08-15

    The nonlinear frequency shift is derived in a transparent asymptotic form for intense Langmuir waves in general collisionless plasma. The formula describes both fluid and kinetic effects simultaneously. The fluid nonlinearity is expressed, for the first time, through the plasma dielectric function, and the kinetic nonlinearity accounts for both smooth distributions and trapped-particle beams. Various known limiting scalings are reproduced as special cases. The calculation avoids differential equations and can be extended straightforwardly to other nonlinear plasma waves.

  1. Observation of ion-cyclotron-frequency mode-conversion flow drive in tokamak plasmas.

    PubMed

    Lin, Y; Rice, J E; Wukitch, S J; Greenwald, M J; Hubbard, A E; Ince-Cushman, A; Lin, L; Porkolab, M; Reinke, M L; Tsujii, N

    2008-12-05

    Strong toroidal flow (Vphi) and poloidal flow (Vtheta) have been observed in D-3He plasmas with ion cyclotron range of frequencies (ICRF) mode-conversion (MC) heating on the Alcator C-Mod tokamak. The toroidal flow scales with the rf power Prf (up to 30 km/s per MW), and is significantly larger than that in ICRF minority heated plasmas at the same rf power or stored energy. The central Vphi responds to Prf faster than the outer regions, and the Vphi(r) profile is broadly peaked for r/a < or =0.5. Localized (0.3 < or = r/a < or =0.5) Vtheta appears when Prf > or =1.5 MW and increases with power (up to 0.7 km/s per MW). The experimental evidence together with numerical wave modeling suggests a local flow drive source due to the interaction between the MC ion cyclotron wave and 3He ions.

  2. Study of some plasma radiative properties based on the frequency fluctuation model approach.

    NASA Astrophysics Data System (ADS)

    Calisti, A.; Mosse, C.; Koubiti, M.; Stamm, R.; Talin, B.

    1995-08-01

    The main ideas of the Frequency Fluctuation Model (FFM), developed to calculate line shapes emitted by multi electron ions in hot and dense plasmas, are summarized. The line shape code which has been based on the FFM is particularly useful in accounting for the so-called ion dynamics effect and permits the tracing of the relevant inhomogeneous characteristics of the radiative patterns at each stage of the calculations. Information about the inhomogeneities of a given line is collected through a numerical coarse-graining process giving rise to microfield dressed two-level systems. These systems mimic the main features of the radiative properties of the emitter and are used as a basis to model the radiative redistribution function, a second order plasma radiative property. The second order theory is discussed and a few examples, calculated for complex emitter systems, are shown.

  3. Cleaning of HT-7 Tokamak Exposed First Mirrors by Radio Frequency Magnetron Sputtering Plasma

    NASA Astrophysics Data System (ADS)

    Yan, Rong; Chen, Junling; Chen, Longwei; Ding, Rui; Zhu, Dahuan

    2014-12-01

    The stainless steel (SS) first mirror pre-exposed in the deposition-dominated environment of the HT-7 tokamak was cleaned in the newly built radio frequency (RF) magnetron sputtering plasma device. The deposition layer on the FM surface formed during the exposure was successfully removed by argon plasma with a RF power of about 80 W and a gas pressure of 0.087 Pa for 30 min. The total reflectivity of the mirrors was recovered up to 90% in the wavelength range of 300-800 nm, while the diffuse reflectivity showed a little increase, which was attributed to the increase of surface roughness in sputtering, and residual contaminants. The FMs made from single crystal materials could help to achieve a desired recovery of specular reflectivity in the future.

  4. Low-frequency fluctuations in scrape-off layer of tokamak plasma with limiter biasing

    NASA Astrophysics Data System (ADS)

    Bisai, N.; Singh, Rameswar; Singh, R.

    2011-12-01

    The effects of limiter biasing on the equilibrium density and potential profiles of the scrape-off layer (SOL) in tokamak plasma are investigated by including ionization and cross-field mobility. It is shown that a broadening of SOL can take place by the inclusion of ionization for low negative biasing. Various microinstabilities relevant for SOL plasmas have been studied. Generalized low-frequency dispersion relation is derived. It is shown that limiter biasing significantly modifies the SOL fluctuations. It is also shown that growth rate of conductive wall instability is smaller for negative biasing than positive biasing case. New mode, the modified Simon-Hoh, and ion temperature gradient instabilities are found to contribute significantly to the growth of curvature- and electron temperature-gradient-driven conductive wall instabilities.

  5. Backreflection diagnostics for ultra-intense laser plasma experiments based on frequency resolved optical gating

    NASA Astrophysics Data System (ADS)

    Wagner, F.; Hornung, J.; Schmidt, C.; Eckhardt, M.; Roth, M.; Stöhlker, T.; Bagnoud, V.

    2017-02-01

    We report on the development and implementation of a time resolved backscatter diagnostics for high power laser plasma experiments at the petawatt-class laser facility PHELIX. Pulses that are backscattered or reflected from overcritical plasmas are characterized spectrally and temporally resolved using a specially designed second harmonic generation frequency resolved optical gating system. The diagnostics meets the requirements made by typical experiments, i.e., a spectral bandwidth of more than 30 nm with sub-nanometer resolution and a temporal window of 10 ps with 50 fs temporal resolution. The diagnostics is permanently installed at the PHELIX target area and can be used to study effects such as laser-hole boring or relativistic self-phase-modulation which are important features of laser-driven particle acceleration experiments.

  6. Electron acceleration in relativistic plasma waves generated by a single frequency short-pulse laser

    SciTech Connect

    Coverdale, C.A.; Darrow, C.B.; Decker, C.D.; Mori, W.B.; Tzeng, K.C., Clayton, C.E.; Marsh, K.A.; Joshi, C.

    1995-04-27

    Experimental evidence for the acceleration of electrons in a relativistic plasma wave generated by Raman forward scattering (SRS-F) of a single-frequency short pulse laser are presented. A 1.053 {mu}m, 600 fsec, 5 TW laser was focused into a gas jet with a peak intensity of 8{times}10{sup 17} W/cm{sup 2}. At a plasma density of 2{times}10{sup 19} cm{sup {minus}3}, 2 MeV electrons were detected and their appearance was correlated with the anti-Stokes laser sideband generated by SRS-F. The results are in good agreement with 2-D PIC simulations. The use of short pulse lasers for making ultra-high gradient accelerators is explored.

  7. Verification of particle simulation of radio frequency waves in fusion plasmas

    SciTech Connect

    Kuley, Animesh; Lin, Z.; Wang, Z. X.; Wessel, F.

    2013-10-15

    Radio frequency (RF) waves can provide heating, current and flow drive, as well as instability control for steady state operations of fusion experiments. A particle simulation model has been developed in this work to provide a first-principles tool for studying the RF nonlinear interactions with plasmas. In this model, ions are considered as fully kinetic particles using the Vlasov equation and electrons are treated as guiding centers using the drift kinetic equation. This model has been implemented in a global gyrokinetic toroidal code using real electron-to-ion mass ratio. To verify the model, linear simulations of ion plasma oscillation, ion Bernstein wave, and lower hybrid wave are carried out in cylindrical geometry and found to agree well with analytic predictions.

  8. Noise control of a flow around a cylinder using high-frequency dielectric barrier discharge plasma actuators

    NASA Astrophysics Data System (ADS)

    Kopiev, V. F.; Belyaev, I. V.; Zaytsev, M. Yu.; Kazansky, P. N.; Kopiev, V. A.; Moralev, I. A.

    2015-03-01

    The effect of high-frequency dielectric barrier discharge plasma actuators on the noise of a flow around a circular cylinder is experimentally studied. It is shown that the plasma actuators are able to reduce the vortex noise of a cylinder within the range of velocities typical for aeroacoustic applications.

  9. Oxygen plasma treatment and deposition of CN{sub x} on a fluorinated polymer matrix composite for improved erosion resistance

    SciTech Connect

    Muratore, C.; Korenyi-Both, A.; Bultman, J. E.; Waite, A. R.; Jones, J. G.; Storage, T. M.; Voevodin, A. A.

    2007-07-15

    The use of polymer matrix composites in aerospace propulsion applications is currently limited by insufficient resistance to erosion by abrasive media. Erosion resistant coatings may provide necessary protection; however, adhesion to many high temperature polymer matrix composite (PMC) materials is poor. A low pressure oxygen plasma treatment process was developed to improve adhesion of CN{sub x} coatings to a carbon reinforced, fluorinated polymer matrix composite. Fullerene-like CN{sub x} was selected as an erosion resistant coating for its high hardness-to-elastic modulus ratio and elastic resilience which were expected to reduce erosion from media incident at different angles (normal or glancing) relative to the surface. In situ x-ray photoelectron spectroscopy was used to evaluate the effect of the plasma treatment on surface chemistry, and electron microscopy was used to identify changes in the surface morphology of the PMC substrate after plasma exposure. The fluorine concentration at the surface was significantly reduced and the carbon fibers were exposed after plasma treatment. CN{sub x} coatings were then deposited on oxygen treated PMC substrates. Qualitative tests demonstrated that plasma treatment improved coating adhesion resulting in an erosion resistance improvement of a factor of 2 compared to untreated coated composite substrates. The combination of PMC pretreatment and coating with CN{sub x} reduced the erosion rate by an order of magnitude for normally incident particles.

  10. Real-time in situ electron spin resonance measurements on fungal spores of Penicillium digitatum during exposure of oxygen plasmas

    NASA Astrophysics Data System (ADS)

    Ishikawa, Kenji; Mizuno, Hiroko; Tanaka, Hiromasa; Tamiya, Kazuhiro; Hashizume, Hiroshi; Ohta, Takayuki; Ito, Masafumi; Iseki, Sachiko; Takeda, Keigo; Kondo, Hiroki; Sekine, Makoto; Hori, Masaru

    2012-07-01

    We report the kinetic analysis of free radicals on fungal spores of Penicillium digitatum interacted with atomic oxygen generated plasma electric discharge using real time in situ electron spin resonance (ESR) measurements. We have obtained information that the ESR signal from the spores was observed and preliminarily assignable to semiquinone radical with a g-value of around 2.004 and a line width of approximately 5G. The decay of the signal is possibly linked to the inactivation of the fungal spore. The real-time in situ ESR has proven to be a useful method to elucidate plasma-induced surface reactions on biological specimens.

  11. Generation of Low-Frequency Electromagnetic Waves by Spectrally Broad Intense Laser Pulses in a Plasma

    NASA Astrophysics Data System (ADS)

    Tsintsadze, L. N.; Tajima, T.; Nishikawa, K.; Koga, J. K.; Nakagawa, K.; Kishimoto, Y.

    A new mechanism for the emission of low-frequency electromagnetic (EM) waves, including the generation of a quasistatic magnetic field, by a relativistically intense laser pulse with a wide spectrum is presented. The emission is due to modulational and filamentational instabilities of the photon gas in a plasma. The generation of the magnetic field is associated with a significant change in the laser pulse shape during the propagation. This process is identified in our 2D particle-in-cell (PIC) simulations with a high intensity (1019

  12. Amorphous hollow carbon spheres synthesized using radio frequency plasma-enhanced chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Yang, G. M.; Xu, Q.; Tian, H. W.; Wang, X.; Zheng, W. T.

    2008-10-01

    We report a method to synthesize amorphous hollow carbon spheres, with diameters ranging from 100 to 800 nm, which are dispersed among bent graphitized carbon nanotubes using radio frequency plasma-enhanced chemical vapour deposition in mixed CH4/H2 gases. The products are characterized by techniques including scanning electron microscopy, energy-dispersive x-ray spectroscopy, Raman spectroscopy and transmission electron microscopy. It is found that MgO and Ni nanoparticles together with hydrogen play important roles in the formation of the spheres. A possible formation mechanism for the carbon composites has been proposed.

  13. Self-focusing of intense high frequency electromagnetic waves in a collisional magnetoactive plasma

    SciTech Connect

    Niknam, A. R.; Hashemzadeh, M.; Aliakbari, A.; Majedi, S.; Haji Mirzaei, F.

    2011-11-15

    The self-focusing of an intense electromagnetic beam in a collisional magnetoactive plasma has been investigated by the perturbation method. Considering the relativistic and ponderomotive nonlinearities and the first three terms of perturbation expansion for the electron density and velocity, the nonlinear wave equation is obtained. This wave equation is solved by applying the source dependent expansion method and the evolution of electromagnetic beam spot-size is discussed. It is shown that the laser spot-size decreases with increasing the collision frequency and external magnetic field strength.

  14. Radio Frequency Generation of an Electron Plasma in a Malmberg-Penning Trap

    SciTech Connect

    Paroli, B.; De Luca, F.; Pozzoli, R.; Rome, M.; Maero, G.

    2010-06-16

    The generation of an electron plasma via low-power Radio Frequency (RF) excitation has been observed in the Malmberg-Penning trap ELTRAP under ultra-high vacuum conditions. The process is sensitive to the RF parameters as well as to the trapping length. The electron heating mechanism necessary to reach the ionization energy of the residual gas has been modeled with the use of a simple one-dimensional iterative map, whose properties show a behavior similar to that of the Fermi acceleration map.

  15. Trench and hole patterning with EUV resists using dual frequency capacitively coupled plasma (CCP)

    NASA Astrophysics Data System (ADS)

    Feurprier, Yannick; Lutker-Lee, Katie; Rastogi, Vinayak; Matsumoto, Hiroie; Chiba, Yuki; Metz, Andrew; Kumar, Kaushik; Beique, Genevieve; Labonte, Andre; Labelle, Cathy; Mignot, Yann; Hamieh, Bassem; Arnold, John

    2015-03-01

    Patterning at 10 nm and sub-10 nm technology nodes is one of the key challenges for the semiconductor industry. Several patterning techniques are under investigation to enable the aggressive pitch requirements demanded by the logic technologies. EUV based patterning is being considered as a serious candidate for the sub-10nm nodes. As has been widely published, a new technology like EUV has its share of challenges. One of the main concerns with EUV resists is that it tends to have a lower etch selectivity and worse LER/LWR than traditional 193nm resists. Consequently the characteristics of the dry etching process play an increasingly important role in defining the outcome of the patterning process. In this paper, we will demonstrate the role of the dual-frequency Capacitively Coupled Plasma (CCP) in the EUV patterning process with regards to improving LER/LWR, resist selectivity and CD tunability for holes and line patterns. One of the key knobs utilized here to improve LER and LWR, involves superimposing a negative DC voltage in RF plasma at one of the electrodes. The emission of ballistic electrons, in concert with the plasma chemistry, has shown to improve LER and LWR. Results from this study along with traditional plasma curing methods will be presented. In addition to this challenge, it is important to understand the parameters needed to influence CD tunability and improve resist selectivity. Data will be presented from a systematic study that shows the role of various plasma etch parameters that influence the key patterning metrics of CD, resist selectivity and LER/LWR. This work was performed by the Research Alliance Teams at various IBM Research and Development Facilities.

  16. Deposition of organosilicone thin film from hexamethyldisiloxane (HMDSO) with 50 kHz/33 MHz dual-frequency atmospheric-pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Jiaojiao, LI; Qianghua, YUAN; Xiaowei, CHANG; Yong, WANG; Guiqin, YIN; Chenzhong, DONG

    2017-04-01

    The deposition of organosilicone thin films from hexamethyldisiloxane(HMDSO) by using a dual-frequency (50 kHz/33 MHz) atmospheric-pressure micro-plasma jet with an admixture of a small volume of HMDSO and Ar was investigated. The topography was measured by using scanning electron microscopy. The chemical bond and composition of these films were analyzed by Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy. The results indicated that the as-deposited film was constituted by silicon, carbon, and oxygen elements, and FTIR suggested the films are organosilicon with the organic component (–CH x ) and hydroxyl functional group(–OH) connected to the Si–O–Si backbone. Thin-film hardness was recorded by an MH–5–VM Digital Micro-Hardness Tester. Radio frequency power had a strong impact on film hardness and the hardness increased with increasing power.

  17. Radio-frequency plasma functionalization of carbon nanotubes surface O2, NH3, and CF4 treatments

    NASA Astrophysics Data System (ADS)

    Felten, A.; Bittencourt, C.; Pireaux, J. J.; van Lier, G.; Charlier, J. C.

    2005-10-01

    Inductive coupled rf-plasma at 13.56 MHz was used to modify multiwalled carbon nanotubes (MWCNTs). This technique can be easily used to tailor the chemical composition of carbon nanotubes by attaching a wide variety of functional groups at their surface: oxygen-, nitrogen-, and fluorine-containing groups have been grafted. The influence of various plasma conditions (power, type of gas, treatment time, pressure, position of the CNT sample inside the chamber) on the functionalization of the MWCNT surface was analyzed by x-ray photoelectron spectroscopy. The results show that for too high oxygen plasma power, chemical etching occurs at the surface of the CNT, thus destroying its structure. On the other hand, for optimal values of the plasma parameters, functional groups (hydroxide, carbonyl, carboxyl, amine, fluorine, etc.) were found to bond to the CNT surface, suggesting that both the concentration and type of the functional groups are in close connection with the plasma conditions. These results were compared to interaction energies predicted by ab initio calculations for different functional groups under consideration, showing that functionalization by oxygen plasma produces mainly functional groups with lower interaction energy.

  18. Frequency-fluctuation model applied to Stark-Zeeman spectral line shapes in plasmas

    SciTech Connect

    Ferri, S.; Calisti, A.; Mosse, C.; Mouret, L.; Talin, B.; Gigosos, M. A.; Gonzalez, M. A.; Lisitsa, V.

    2011-08-15

    A very fast method for calculating line shapes in the presence of an external magnetic field accounting for charge particle dynamics is proposed. It is based on a reformulation of the frequency fluctuation model, which provides an expression of the dynamic line shape as a functional of the static distribution function of frequencies. In the presence of an external magnetic field, the distribution of intensity and polarization of the emission depends on the angle between the observation line and the magnetic field's direction. Comparisons with numerical simulations and experimental results for various plasma conditions show very good agreement. Results on hydrogen lines in the context of magnetic fusion and the Lyman-{alpha} line, accounting for fine structure, emitted by argon in the context of inertial fusion, are also presented.

  19. Comment on "Mode Conversion of Waves In The Ion-Cyclotron Frequency Range in Magnetospheric Plasmas"

    SciTech Connect

    Kim, Eun; Johnson, J. R.

    2014-02-01

    Recently, Kazakov and Fulop [1] studied mode conversion (MC) at the ion-ion hybrid (IIH) resonance in planetary magnetospheric plasmas by simplifying the dispersion relation of the fast wave (FW) modes to describe a cutoff-resonance (CR) pair near the IIH resonance, which can be reduced to a Budden problem. They suggested that when the IIH resonance frequency (ωS) approaches the crossover frequency (ωcr), and the parallel wavenumber (k∥) is close to the critical wavenumber k* ∥(ωS = ωcr), MC can be efficient for arbitrary heavy ion density ratios. In this Comment, we argue that (a) the FW dispersion relation cannot be simplified to the CR pair especially near ωcr because in many parameter regimes there is a cutoff-resonance-cutoff (CRC) triplet that completely changes the wave absorption; and (b) the maximum MC efficiency does not always occur near k∥ ≈ k*∥∥.

  20. High-frequency Plasma Waves Associated with Magnetic Reconnection in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Wang, Y.

    2015-12-01

    Activities of high-frequency plasma waves associated with magnetic reconnection in the solar wind observed by Time Domain Sampler (TDS) experiments on STEREO/WAVES are preliminarily analyzed. The TDS instrument can provide burst mode electric fields data with as long as 16384 sample points at 250 kHz sampling rate. In all 1120 suspected reconnection events, it is found that the most commonly occurred waves are neither ion acoustic waves, electrostatic solitary waves, nor Langmuir/upper hybrid waves, but Bernstein-like waves with harmonics of the electron cyclotron frequency. In addition, to each type of waves, Langmuir/upper hybrid waves reveal the largest occurrence rate in the reconnection region than in the ambient solar wind. These results indicate that Bernstein-like waves and Langmuir/upper hybrid waves might play important roles in the reconnection associated particle heating processes and they might also influence the dissipation of magnetic reconnection.

  1. Optical emission spectroscopic diagnostics of a non-thermal atmospheric pressure helium-oxygen plasma jet for biomedical applications

    NASA Astrophysics Data System (ADS)

    Thiyagarajan, Magesh; Sarani, Abdollah; Nicula, Cosmina

    2013-06-01

    In this work, we have applied optical emission spectroscopy diagnostics to investigate the characteristics of a non-thermal atmospheric pressure helium plasma jet. The discharge characteristics in the active and afterglow region of the plasma jet, that are critical for biomedical applications, have been investigated. The voltage-current characteristics of the plasma discharge were analyzed and the average plasma power was measured to be around 18 W. The effect of addition of small fractions of oxygen at 0.1%-0.5% on the plasma jet characteristics was studied. The addition of oxygen resulted in a decrease in plasma plume length due to the electronegativity property of oxygen. Atomic and molecular lines of selected reactive plasma species that are considered to be useful to induce biochemical reactions such as OH transitions A2Σ+(ν=0,1)→X2Π(Δν =0) at 308 nm and A2Σ+(ν=0,1)→X2Π(Δν =1) at 287 nm, O I transitions 3p5P→3s5S0 at 777.41 nm, and 3p3P→3s3S0 at 844.6 nm, N2(C-B) second positive system with electronic transition C3Πu→B3Πg in the range of 300-450 nm and N2+(B-X) first negative system with electronic transition B2Σu+→X2Σg+(Δν =0) at 391.4 nm have been studied. The atomic emission lines of helium were identified, including the He I transitions 3p3P0→2s3S at 388.8 nm, 3p1P0→ 2s1S at 501.6 nm, 3d3D→2p3P0 at 587.6 nm, 3d1D→2p1P0 at 667.8 nm, 3s3S1→2p3P0 at 706.5 nm, 3s1S0→2p1P0 at 728.1 nm, and Hα transition 2p-3d at 656.3 nm. Using a spectral fitting method, the OH radicals at 306-312 nm, the rotational and vibrational temperatures equivalent to gas temperatures of the discharge was measured and the effective non-equilibrium nature of the plasma jet was demonstrated. Our results show that, in the entire active plasma region, the gas temperature remains at 310 ± 25 K and 340 ± 25 K and it increases to 320 ± 25 K and 360 ± 25 K in the afterglow region of the plasma jet for pure helium and helium/oxygen (0.1%) mixture

  2. Undoped InOx films deposited by radio frequency plasma enhanced reactive thermal evaporation at room temperature: importance of substrate.

    PubMed

    Parreira, P; Lavareda, G; Valente, J; Nunes, F T; Amaral, A; de Carvalho, C Nunes

    2010-04-01

    Conductive and transparent undoped thin films of indium oxide (InOx ), 120 nm average thick, were deposited by radio frequency plasma enhanced reactive thermal evaporation (rf-PERTE) of indium in the presence of oxygen at room temperature. Several substrates were used in order to study their influence on the main properties of these films: alkali free (AF) glass, fused silica, crystalline silicon and polyethylene terephthalate (PET). Surface morphology of the InOx films as a function of the substrates was observed by SEM and showed that the undoped InOx films obtained are nanostructured. For the c-Si substrate, InOx films with increased grain size are obtained, induced by the crystalline substrate. Films deposited on fused silica and AF glass substrates show a nano-grainy surface with similar surface morphologies. The InOx films deposited on AF glass show the highest values of both: electrical conductivity of about 1100 (omega cm)(-1) and visible transmittance of 85%. The substrate has a greater influence on the surface morphology of the films when a polymer (PET) is used. InOx films deposited on PET show a decrease in the electrical conductivity (90 (omega cm)(-1)) and a slight decrease in the average visible transmittance (78%).

  3. [Spectral analysis of oxygen radical in a synergistic system of pulsed discharge plasma/TiO2].

    PubMed

    Wang, Hui-Juan; Li, Jie; Chu, Jin-Yu

    2011-01-01

    Based on the synergistic effect of pulsed discharge plasma and titanium dioxide (TiO2) photocatalysis, a coupling system of pulsed discharge plasma/TiO2 was set up in the present paper, by using the ultraviolet radiation produced during the pulsed discharge process. TiO2 film immobilized on the glass beads was used as the photocatalyst in the synergistic system. In the research, the synergistic mechanism of pulsed discharge plasma and TiO2 photocatalysis was reviewed by the spectral diagnosis of oxygen radical (* O radical) produced in different reaction systems. The obtained results showed that the characteristic emission spectrum of * O radical could be observed at 777 nm and the corresponding transitions was 3p5 P --> 3s5 S. When air was used as bubbling gas, the relative emission intensity of * O radical recorded in the synergistic system was stronger than that in the plasma alone system, and the same result was also obtained when oxygen (O2) was used as bubbling gas. This result revealed that the photocatalytic activity of the immobilized TiO2 in the synergistic system could be induced by the ultraviolet radiation formed during the pulsed discharge process. In the systems of pulsed discharge plasma alone and pulsed discharge plasma combined with TiO2 photocatalysis, the relative emission intensity of * O radical in distilled water was stronger than that in phenol solutions. The results showed that * O radical was one of responsible radicals for phenol degradation in the pulsed discharge plasma alone system as well as the synergistic system.

  4. Extremely high wear resistance and ultra-low friction behaviour of oxygen-plasma-treated nanocrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Radhika, R.; Kumar, N.; Sankaran, K. J.; Dumpala, Ravikumar; Dash, S.; Ramachandra Rao, M. S.; Arivuoli, D.; Tyagi, A. K.; Tai, N. H.; Lin, I.-Nan

    2013-10-01

    The diamond nanowire (DNW) film was deposited by N2-enriched microwave plasma-enhanced chemical vapour deposition (MPECVD) process. As-deposited DNW film was treated in O2 plasma which resulted in chemical and microstructural modification. Sheath of the DNW film is chemically constituted by amorphous carbon (a-C)- and graphite (sp2C=C)-like bonding. However, nanowires transformed into ultra-small spherical grains after the O2-plasma treatments. In this condition, a-C and sp2C=C bonding significantly reduced due to plasma etching caused by oxygen atoms. After the O2-plasma treatment, formation of functional groups such as C=O, C-O-C, O-H, O-CH3 and H2O was observed on the surface and inside the wear track as evident from the micro FTIR analysis. H2O is hydrogen bonded to oxygen-containing groups such as -OH and -H. The O2-plasma-exposed DNW film exhibits surface charging and causes formation of dangling bonds and electron trapping centres. This results in significant decrease in contact angle, hence superhydrophilic behaviour. The friction coefficient of O2-plasma-treated film showed super low value ˜0.002 with high wear resistance 2 × 10-12 mm3 N-1 m-1. In the reciprocating ball-on-disc tribology test, only ˜80 nm wear loss was observed after the 1 km of sliding distance at 10 N loads. Such an advance in tribological properties is explained by passivation of covalent carbon bonding and transformation of sliding surfaces by weak van der Waals and hydrogen bondings. High surface energy and the consequent superhydrophilic behaviour of film is attributed to the formation of the above-mentioned functional groups on the surface. This protects against deformation of the wear track leading to extremely high wear resistance.

  5. First Observation of a (1,0) Mode Frequency Shift of an Electron Plasma at Antiproton Beam Injection

    NASA Astrophysics Data System (ADS)

    Kuroda, N.; Mohri, A.; Torii, H. A.; Nagata, Y.; Shibata, M.

    2014-07-01

    The frequency shift of the center-of-mass oscillation, known as the (1,0) mode, of a trapped electron plasma and, furthermore, its time evolution were observed during the cooling of an injected antiproton beam for the first time. Here, antiprotons mixed with the electrons did not follow faster electron oscillations but contributed to the modification of the effective potential. The time evolution of the plasma temperature, deduced from the frequency shift of the excited (3,0) mode, suggested that there was an abnormal energy deposition of the antiproton beam in the electron plasma before thermalization.

  6. Model polymer etching and surface modification by a time modulated RF plasma jet: role of atomic oxygen and water vapor

    NASA Astrophysics Data System (ADS)

    Luan, P.; Knoll, A. J.; Wang, H.; Kondeti, V. S. S. K.; Bruggeman, P. J.; Oehrlein, G. S.

    2017-01-01

    The surface interaction of a well-characterized time modulated radio frequency (RF) plasma jet with polystyrene, poly(methyl methacrylate) and poly(vinyl alcohol) as model polymers is investigated. The RF plasma jet shows fast polymer etching but mild chemical modification with a characteristic carbonate ester and NO formation on the etched surface. By varying the plasma treatment conditions including feed gas composition, environment gaseous composition, and treatment distance, we find that short lived species, especially atomic O for Ar/1% O2 and 1% air plasma and OH for Ar/1% H2O plasma, play an essential role for polymer etching. For O2 containing plasma, we find that atomic O initiates polymer etching and the etching depth mirrors the measured decay of O atoms in the gas phase as the nozzle-surface distance increases. The etching reaction probability of an O atom ranging from 10-4 to 10-3 is consistent with low pressure plasma research. We also find that adding O2 and H2O simultaneously into Ar feed gas quenches polymer etching compared to adding them separately which suggests the reduction of O and OH density in Ar/O2/H2O plasma.

  7. On the history of plasma treatment and comparison of microbiostatic efficacy of a historical high-frequency plasma device with two modern devices

    PubMed Central

    Napp, Judith; Daeschlein, Georg; Napp, Matthias; von Podewils, Sebastian; Gümbel, Denis; Spitzmueller, Romy; Fornaciari, Paolo; Hinz, Peter; Jünger, Michael

    2015-01-01

    Background: Cold atmospheric pressure plasma (CAP) with its many bioactive properties has defined a new medical field: the plasma medicine. However, in the related form of high-frequency therapy, CAP was even used briefly a century ago. The aim of this study was to review historic CAP treatments and to obtain data regarding the antimicrobial efficacy of a historical high-frequency plasma device. Methods: First, historic literature regarding the history of CAP treatment was evaluated, because in the modern literature no data were available. Second, the susceptibility of 5 different bacterial wound isolates, cultured on agar, to a historic plasma source (violet wand [VW]) and two modern devices (atmospheric pressure plasma jet [APPJ] and Dielectric Barrier Discharge [DBD]) was analyzed . The obtained inhibition areas (IA) were compared. Results: First, the most convenient popular historical electromedical treatments produced a so-called effluvia by using glass electrodes, related to today’s CAP. Second, all three tested plasma sources showed complete eradication of all tested microbial strains in the treated area. The “historical” cold VW plasma showed antimicrobial effects similar to those of modern APPJ and DBD regarding the diameter of the IA. Conclusion: Some retrograde evidence may be deducted from this, especially for treatment of infectious diseases with historical plasma devices. The underlying technology may serve as model for construction of modern sucessive devices. PMID:26124985

  8. Spectroscopy diagnostic of dual-frequency capacitively coupled CHF{sub 3}/Ar plasma

    SciTech Connect

    Liu, Wen-Yao; Du, Yong-Quan; Liu, Yong-Xin; Liu, Jia; Zhao, Tian-Liang; Wang, You-Nian; Xu, Yong; Li, Xiao-Song; Zhu, Ai-Min

    2013-11-15

    A combined spectroscopic method of absorption, actinometry, and relative optical emission intensity is employed to determine the absolute CF{sub 2} density, the relative F and H densities, H atom excitation temperature and the electron density in dual-frequency (60/2 MHz) capacitively coupled CHF{sub 3}/Ar plasmas. The effects of different control parameters, such as high-frequency (HF) power, low-frequency (LF) power, gas pressure, gap length and content of CHF{sub 3}, on the concentration of radical CF{sub 2}, F, and H and excitation temperature are discussed, respectively. It is found that the concentration of CF{sub 2} is strongly dependent on the HF power, operating pressure and the proportion of CHF{sub 3} in feed gas, while it is almost independent of the LF power and the gap length. A higher concentration ratio of F to CF{sub 2} could be obtained in dual-frequency discharge case. Finally, the generation and decay mechanisms of CF{sub 2} and F were also discussed.

  9. Seasonal plasticity of auditory hair cell frequency sensitivity correlates with plasma steroid levels in vocal fish

    PubMed Central

    Rohmann, Kevin N.; Bass, Andrew H.

    2011-01-01

    SUMMARY Vertebrates displaying seasonal shifts in reproductive behavior provide the opportunity to investigate bidirectional plasticity in sensory function. The midshipman teleost fish exhibits steroid-dependent plasticity in frequency encoding by eighth nerve auditory afferents. In this study, evoked potentials were recorded in vivo from the saccule, the main auditory division of the inner ear of most teleosts, to test the hypothesis that males and females exhibit seasonal changes in hair cell physiology in relation to seasonal changes in plasma levels of steroids. Thresholds across the predominant frequency range of natural vocalizations were significantly less in both sexes in reproductive compared with non-reproductive conditions, with differences greatest at frequencies corresponding to call upper harmonics. A subset of non-reproductive males exhibiting an intermediate saccular phenotype had elevated testosterone levels, supporting the hypothesis that rising steroid levels induce non-reproductive to reproductive transitions in saccular physiology. We propose that elevated levels of steroids act via long-term (days to weeks) signaling pathways to upregulate ion channel expression generating higher resonant frequencies characteristic of non-mammalian auditory hair cells, thereby lowering acoustic thresholds. PMID:21562181

  10. Oxygen plasma surface modification augments poly(L-lactide-co-glycolide) cytocompatibility toward osteoblasts and minimizes immune activation of macrophages.

    PubMed

    Scislowska-Czarnecka, Anna; Szmigiel, Dariusz; Genet, Michel; Dupont-Gillain, Christine; Pamula, Elzbieta; Kolaczkowska, Elzbieta

    2015-12-01

    Here, we report on modification of one of the model biomedical polymers, poly L-lactide-co-glycolide (PLGA; 85:15), by reactive ion etching (RIE) oxygen plasma treatment. PLGA's major disadvantage is high hydrophobicity which restrains binding of cell-adhesive proteins and host cells. In the current approach, we aimed to answer two questions: (1) will only short (10 s) and moderate (20-200 mTorr, 45-90 W) RIE oxygen plasma treatment, leading to decrease of water contact angle by only up to 10°, sufficiently improve PLGA adherence to cells, and (2) how will this affect osteoblasts and activation of the immune system? All obtained modified PLGAs had improved hydrophilicity but unaltered roughness (as revealed by water contact angle measurements, X-ray photoelectron spectroscopy, and atomic force microscopy) resulting in significantly improved adhesion of osteoblasts (MG-63) and their low activation. Importantly, macrophages (RAW 264.7), one of the key cells initiating inflammation and bone resorption, responded significantly less vigorously to the modified polymers, expressing/releasing lower amounts of nitric oxide, matrix metalloproteinases (MMP-9), and pro-inflammatory cytokines (TNF-α, IL-6, IL-12p70, IFN-γ, IL-10). We conclude that already slight RIE oxygen plasma modification of PLGA is sufficient to improve its surface properties, and enhance cytocompatibility. Most importantly, this type of modification prevents excessive immune response.

  11. Surface modification of PdlLGA microspheres with gelatine methacrylate: Evaluation of adsorption, entrapment, and oxygen plasma treatment approaches.

    PubMed

    Baki, Abdulrahman; Rahman, Cheryl V; White, Lisa J; Scurr, David J; Qutachi, Omar; Shakesheff, Kevin M

    2017-01-16

    Injectable poly (dl-lactic-co-glycolic acid) (PdlLGA) microspheres are promising candidates as biodegradable controlled release carriers for drug and cell delivery applications; however, they have limited functional groups on the surface to enable dense grafting of tissue specific biocompatible molecules. In this study we have evaluated surface adsorption, entrapment and oxygen plasma treatment as three approaches to modify the surfaces of PdlLGA microspheres with gelatine methacrylate (gel-MA) as a biocompatible and photo cross-linkable macromolecule. Time of flight secondary ion mass spectroscopy (TOF SIMS) and X-ray photoelectron spectroscopy (XPS) were used to detect and quantify gel-MA on the surfaces. Fluorescent and scanning electron microscopies (SEM) were used to image the topographical changes. Human mesenchymal stem cells (hMSCs) of immortalised cell line were cultured on the surface of gel-MA modified PdlLGA microspheres and Presto-Blue assay was used to study the effect of different surface modifications on cell proliferation. Data analysis showed that the oxygen plasma treatment approach resulted in the highest density of gel-MA deposition. This study supports oxygen plasma treatment as a facile approach to modify the surface of injectable PdlLGA microspheres with macromolecules such as gel-MA to enhance proliferation rate of injected cells and potentially enable further grafting of tissue specific molecules.

  12. The characteristics of Ta2O5 films deposited by radio frequency pure oxygen ion assisted deposition (RFOIAD) technology

    NASA Astrophysics Data System (ADS)

    Han, Jinghua; Zhang, Qiuhui; Fan, Weixing; Feng, Guoying; Li, Yaguo; Wei, Aixiang; Hu, Ruifeng; Gu, Qiongqiong

    2017-02-01

    The characteristics of Ta2O5 films deposited by radio frequency pure oxygen ion assisted deposition (RFOIAD) technology were compared to a gas mixture of oxygen and argon (O2/Ar) ion beam assisted deposition experimentally and theoretically, inclusive of optical, electronic, and laser-induced damage resistance. The results showed that the RFOIAD could make removal of the pinholes and oxygen vacancies in the film and increase of the band gap, which resulted in the enhancement of refractive index, breakdown voltage, and the diminution of absorptivity as well as leakage current. The laser induced damage testing suggested that the damage induced damage threshold of the film deposited by RFOIAD could be increased, but the cracks appeared easily due to the concentration of thermal stress. While for the Ta2O5 film deposited using a sputtering gas of the mixtures of oxygen and argon, the porous characteristics were helpful to relief the thermal stress concentration, and the formation of cracks can be avoided.

  13. Numerical Simulation of Waves Driven by Plasma Currents Generated by Low-Frequency Alfven Waves in a Multi-Ion Plasma

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Khazanov, George

    2004-01-01

    When multi-ion plasma consisting of heavy and light ions is permeated by a low-frequency Alfven (LFA) wave, the crossed-electric-and-magnetic field (E x B), and the polarization drifts of the different ion species and the electrons could be quite different. The relative drifts between the charged-particle species drive waves, which energize the plasma. Using 2.5-dimensional (2.5-D) particle-in-cell simulations, we study this process of wave generation and its nonlinear consequences in terms of acceleration and heating plasma. Specifically, we study the situation for LFA wave frequency being lower than the heavy-ion cyclotron frequency in a multi-ion plasma. We impose such a wave to the plasma assuming that its wavelength is much larger than that of the waves generated by the relative drifts. For better understanding, the LFA-wave driven simulations are augmented by those driven by initialized ion beams. The driven high-frequency (HF) wave modes critically depend on the heavy ion density nh; for small values of nh, the lower hybrid (LH) waves dominate. On the other hand, for large nh a significantly enhanced level of waves occurs over a much broader frequency spectrum below the LH frequency and such waves are interpreted here as the ion Bernstein (IB) mode near the light ion cyclotron harmonics. Irrespective of the driven wave modes, both the light and heavy ions undergo significant transverse acceleration, but for the large heavy-ion densities, even the electrons are significantly accelerated in the parallel direction by the waves below the LH frequency. Even when the LFA wave drive is maintained, the ion heating leads to the cessation of HF wave excitation just after a few cycles of the former wave. On the basis of marginal stability seen in the simulations, an empirical relation for LFA wave amplitude, frequency and ion temperature is given.

  14. Parametric investigations of striations in electronegative capacitively coupled radio-frequency plasmas

    NASA Astrophysics Data System (ADS)

    Liu, Yong-Xin; Schungel, Edmund; Korolov, Ihor; Donko, Zoltan; Schulze, Julian; Wang, You-Nian

    2016-09-01

    Striated structures in light emission have been observed by Phase Resolved Optical Emission Spectroscopy (PROES) and analyzed based on particle-based kinetic simulations in capacitively coupled rf CF4 plasmas. On this basis, we conduct a systematic study on the effects of external parameters on the striated structure by PROES and particle-based kinetic simulations. Our results exhibit that at 100 Pa pressure and 300 V voltage amplitude striations generally occur within a certain driving frequency range, i.e., between 2 MHz and 18 MHz, and the distance between the ion density maxima decreases with rising driving frequency. A mode discharge transition from the ``drift-ambipolar'' into ``striation'' mode could be observed by increasing the pressure or rf voltage. The reasons for these observations are further understood by the analytical solution of a simply model of the ion-ion plasma. This work has been supported by the National Natural Science Foundation of China (NSFC) (Grant Nos. 11335004 and 11405018).

  15. Formation and characteristics of patterns in atmospheric-pressure radio-frequency dielectric barrier discharge plasma

    NASA Astrophysics Data System (ADS)

    Yang, Lizhen; Liu, Zhongwei; Mao, Zhiguo; Li, Sen; Chen, Qiang

    2017-01-01

    The patterns in radio-frequency dielectric barrier discharge (RF DBD) are studied at atmospheric pressure of argon (Ar) or helium (He) mixed with nitrogen (N2) gas. When a small amount of N2 is mixed with He or Ar gas, discharge patterns are formed. In a N2/He gas mixture, besides the filament discharge that forms patterns, a glow background discharge is also observed, whereas only the filament discharge forms patterns in a N2/Ar gas mixture. The resolution of the hexagonal pattern as a function of applied power and gas flow rate is then explored. On the basis of spatial-temporal images taken using an intensified charge-coupled device (ICCD), we find that there is no interleaving of two transient hexagon sublattices in N2/Ar or N2/He plasma in RF DBD patterns, which are totally different from those in which surface charges dominated in the mid-frequency DBD plasma. This supports our hypothesis that the bulk charges dominate the pattern formation in RF DBD.

  16. The stability of radio-frequency plasma-treated polydimethylsiloxane surfaces.

    PubMed

    Chen, I-Jane; Lindner, Ernö

    2007-03-13

    Polydimethylsiloxane (PDMS) is a widely used material for manufacturing lab-on-chip devices. However, the hydrophobic nature of PDMS is a disadvantage in microfluidic systems. To transform the hydrophobic PDMS surface to hydrophilic, it was treated with radio-frequency (RF) air plasma at 150, 300, and 500 mTorr pressures for up to 30 min. Following the surface treatment, the PDMS specimens were stored in air, deionized water, or 0.14 M NaCl solution at 4 degrees C, 20 degrees C, and 70 degrees C. The change in the hydrophilicity (wettability) of the PDMS surfaces was followed by contact angle measurements and Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy as a function of time. As an effect of the RF plasma treatment, the contact angles measured on PDMS surfaces dropped from 113 +/- 4 degrees to 9 +/- 3 degrees . The chamber pressure and the treatment time had no or negligible effect on the results. However, the PDMS surface gradually lost its hydrophilic properties in time. The rate of this process is influenced by the difference in the dielectric constants of the PDMS and its ambient environment. It was the smallest at low temperatures in deionized water and largest at high temperatures in air. Apparently, the OH groups generated on the PDMS surface during the plasma treatment tended toward a more hydrophilic/less hydrophobic environment during the relaxation processes. The correlation between the FTIR-ATR spectral information and the contact angle data supports this interpretation.

  17. A computationally assisted spectroscopic technique to measure secondary electron emission coefficients in radio frequency plasmas

    NASA Astrophysics Data System (ADS)

    Daksha, M.; Berger, B.; Schuengel, E.; Korolov, I.; Derzsi, A.; Koepke, M.; Donkó, Z.; Schulze, J.

    2016-06-01

    A computationally assisted spectroscopic technique to measure secondary electron emission coefficients (γ-CAST) in capacitively-coupled radio-frequency plasmas is proposed. This non-intrusive, sensitive diagnostic is based on a combination of phase resolved optical emission spectroscopy and particle-based kinetic simulations. In such plasmas (under most conditions in electropositive gases) the spatio-temporally resolved electron-impact excitation/ionization rate features two distinct maxima adjacent to each electrode at different times within each RF period. While one maximum is the consequence of the energy gain of electrons due to sheath expansion, the second maximum is produced by secondary electrons accelerated towards the plasma bulk by the sheath electric field at the time of maximum voltage drop across the adjacent sheath. Due to these different excitation/ionization mechanisms, the ratio of the intensities of these maxima is very sensitive to the secondary electron emission coefficient γ. This sensitvity, in turn, allows γ to be determined by comparing experimental excitation profiles and simulation data obtained with various γ-coefficients. The diagnostic, tested here in a geometrically symmetric argon discharge, yields an effective secondary electron emission coefficient of γ =0.066+/- 0.01 for stainless steel electrodes.

  18. The role of high frequency oscillations in the penetration of plasma clouds across magnetic boundaries

    SciTech Connect

    Hurtig, Tomas; Brenning, Nils; Raadu, Michael A.

    2005-01-01

    Experiments are reported where a collissionfree plasma cloud penetrates a magnetic barrier by self-polarization. Three closely related effects, all fundamental for the penetration mechanism, are studied quantitatively: (1) anomalous fast magnetic field penetration (two orders of magnitude faster than classical) (2) anomalous fast electron transport (three orders of magnitude faster than classical and two orders of magnitude faster than Bohm diffusion), and (3) the ion energy budget as ions enter the potential structure set up by the self-polarized plasma cloud. It is concluded that all three phenomena are closely related and that they are mediated by highly nonlinear oscillations in the lower hybrid range, driven by a strong diamagnetic current loop which is set up in the plasma in the penetration process. The fast magnetic field penetration occurs as a consequence of the anomalous resistivity caused by the wave field and the fast electron transport across magnetic field lines is caused by the correlation between electric field and density oscillations in the wave field. It is also found that ions do not lose energy in proportion to the potential 'hill' they have to climb, rather they are transported against the dc potential structure by the same correlation that is responsible for the electron transport. The results obtained through direct measurements are compared to particle in cell simulations that reproduce most aspects of the high frequency wave field.

  19. High frequency core localized modes in neutral beam heated plasmas on TFTR

    SciTech Connect

    Nazikian, R.; Chang, Z.; Fredrickson, E.D.

    1995-11-01

    A band of high frequency modes in the range 50--150 kHz with intermediate toroidal mode numbers 4 < n < 10 are commonly observed in the core of supershot plasmas on TFTR. Two distinct varieties of MHD modes are identified corresponding to a flute-like mode predominantly appearing around the q = 1 surface and an outward ballooning mode for q > 1. The flute-like modes have nearly equal amplitude on the high field and low field side of the magnetic axis and are mostly observed in moderate performance supershot plasmas with {tau}{sub E} < 2{tau}{sub L} while the ballooning-like modes have enhanced amplitude on the low field side of the magnetic axis and tend to appear in higher performance supershot plasmas with {tau}{sub E} > 2{tau}{sub L}, where {tau}{sub L} is the equivalent L-mode confinement time. The modes propagate in the ion diamagnetic drift direction and are highly localized with radial widths {Delta}r {approximately} 5--10 cm, fluctuation levels {tilde n}/n, {tilde T}{sub e}/T{sub e} < 0.01, and radial displacements {zeta}{sub r} {approximately} 0.1 cm. Unlike the toroidally localized high-n activity observed just prior to major and minor disruptions on TFTR, these modes are typically much weaker, more benign, and may be indicative of kinetic ballooning modes destabilized by resonant circulating neutral beam ions.

  20. Reactive molecular dynamics simulations of oxygen species in a liquid water layer of interest for plasma medicine

    NASA Astrophysics Data System (ADS)

    Yusupov, M.; Neyts, E. C.; Simon, P.; Berdiyorov, G.; Snoeckx, R.; van Duin, A. C. T.; Bogaerts, A.

    2014-01-01

    The application of atmospheric pressure plasmas in medicine is increasingly gaining attention in recent years, although very little is currently known about the plasma-induced processes occurring on the surface of living organisms. It is known that most bio-organisms, including bacteria, are coated by a liquid film surrounding them, and there might be many interactions between plasma species and the liquid layer before the plasma species reach the surface of the bio-organisms. Therefore, it is essential to study the behaviour of the reactive species in a liquid film, in order to determine whether these species can travel through this layer and reach the biomolecules, or whether new species are formed along the way. In this work, we investigate the interaction of reactive oxygen species (i.e. O, OH, HO2 and H2O2) with water, which is assumed as a simple model system for the liquid layer surrounding biomolecules. Our computational investigations show that OH, HO2 and H2O2 can travel deep into the liquid layer and are hence in principle able to reach the bio-organism. Furthermore, O, OH and HO2 radicals react with water molecules through hydrogen-abstraction reactions, whereas no H-abstraction reaction takes place in the case of H2O2. This study is important to gain insight into the fundamental operating mechanisms in plasma medicine, in general, and the interaction mechanisms of plasma species with a liquid film, in particular.

  1. An atmospheric-pressure cold plasma leads to apoptosis in Saccharomyces cerevisiae by accumulating intracellular reactive oxygen species and calcium

    NASA Astrophysics Data System (ADS)

    Ma, R. N.; Feng, H. Q.; Liang, Y. D.; Zhang, Q.; Tian, Y.; Su, B.; Zhang, J.; Fang, J.

    2013-07-01

    A non-thermal plasma is known to induce apoptosis of various cells but the mechanism is not yet clear. A eukaryotic model organism Saccharomyces cerevisiaewas used to investigate the cellular and biochemical regulations of cell apoptosis and cell cycle after an atmospheric-pressure cold plasma treatment. More importantly, intracellular calcium (Ca2+) was first involved in monitoring the process of plasma-induced apoptosis in this study. We analysed the cell apoptosis and cell cycle by flow cytometry and observed the changes in intracellular reactive oxygen species (ROS) and Ca2+ concentration, cell mitochondrial membrane potential (Δψm) as well as nuclear DNA morphology via fluorescence staining assay. All experimental results indicated that plasma-generated ROS leads to the accumulation of intracellular ROS and Ca2+ that ultimately contribute to apoptosis associated with cell cycle arrest at G1 phase through depolarization of Δψm and fragmenting nuclear DNA. This work provides a novel insight into the physical and biological mechanism of apoptosis induced by a plasma which could benefit for promoting the development of plasmas applied to cancer therapy.

  2. Tuning the electrical property via defect engineering of single layer MoS2 by oxygen plasma.

    PubMed

    Islam, Muhammad R; Kang, Narae; Bhanu, Udai; Paudel, Hari P; Erementchouk, Mikhail; Tetard, Laurene; Leuenberger, Michael N; Khondaker, Saiful I

    2014-09-07

    We have demonstrated that the electrical property of single-layer molybdenum disulfide (MoS2) can be significantly tuned from the semiconducting to the insulating regime via controlled exposure to oxygen plasma. The mobility, on-current and resistance of single-layer MoS2 devices were varied by up to four orders of magnitude by controlling the plasma exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory studies suggest that the significant variation of electronic properties is caused by the creation of insulating MoO3-rich disordered domains in the MoS2 sheet upon oxygen plasma exposure, leading to an exponential variation of resistance and mobility as a function of plasma exposure time. The resistance variation calculated using an effective medium model is in excellent agreement with the measurements. The simple approach described here can be used for the fabrication of tunable two-dimensional nanodevices based on MoS2 and other transition metal dichalcogenides.

  3. Deposition and properties of high-velocity-oxygen-fuel and plasma-sprayed Mo-Mo2C composite coatings

    NASA Astrophysics Data System (ADS)

    Prchlik, L.; Gutleber, J.; Sampath, S.

    2001-12-01

    Molybdenum thermal-spray coatings, dispersion strengthened by molybdenum oxides and molybdenum carbides, play an important role in industrial tribological applications. Traditionally, they have been prepared by plasma and wire flame spraying. High porosity and lower cohesion strength limit their application in situations where both galling and abrasion wear is involved. In this study, high-velocity-oxygen-fuel (HVOF) deposition of molybdenum and molybdenum carbide coatings was attempted. Deposition was achieved for all powders used. Composition, microstructure, mechanical, and wear properties of the HVOF synthesized coatings were evaluated and compared with plasma-sprayed counterparts. The HVOF coatings possessed a very good abrasion resistance, whereas plasma deposits performed better in dry sliding tests. Measurements showed a close relationship between the coating surface hardness and its abrasion resistance. Results also suggested correlation between molybdenum carbide distribution in the molybdenum matrix and the sliding friction response of Mo-Mo2C coatings.

  4. Effect of oxygen plasma on field emission characteristics of single-wall carbon nanotubes grown by plasma enhanced chemical vapour deposition system

    SciTech Connect

    Kumar, Avshish; Parveen, Shama; Husain, Samina; Ali, Javid; Zulfequar, Mohammad; Harsh; Husain, Mushahid

    2014-02-28

    Field emission properties of single wall carbon nanotubes (SWCNTs) grown on iron catalyst film by plasma enhanced chemical vapour deposition system were studied in diode configuration. The results were analysed in the framework of Fowler-Nordheim theory. The grown SWCNTs were found to be excellent field emitters, having emission current density higher than 20 mA/cm{sup 2} at a turn-on field of 1.3 V/μm. The as grown SWCNTs were further treated with Oxygen (O{sub 2}) plasma for 5 min and again field emission characteristics were measured. The O{sub 2} plasma treated SWCNTs have shown dramatic improvement in their field emission properties with emission current density of 111 mA/cm{sup 2} at a much lower turn on field of 0.8 V/μm. The as grown as well as plasma treated SWCNTs were also characterized by various techniques, such as scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy before and after O{sub 2} plasma treatment and the findings are being reported in this paper.

  5. Oxygen-Plasma-Treated Indium-Tin-Oxide Films on Nonalkali Glass Deposited by Super Density Arc Plasma Ion Plating

    NASA Astrophysics Data System (ADS)

    Kim, Soo Young; Hong, Kihyon; Son, Jun Ho; Jung, Gwan Ho; Lee, Jong-Lam; Choi, Kyu Han; Song, Kyu Ho; Ahn, Kyung Chul

    2008-02-01

    The effects of O2 plasma treatment on both the chemical composition and work function of an indium-tin-oxide (ITO) film were investigated. ITO films were deposited on non-alkali glass substrate by super density arc plasma ion plating for application in active-matrix organic light-emitting diodes (OLEDs). The water contact angle decreased from 38 to 11° as the ITO films were treated with O2 plasma for 60 s at a plasma power of 150 W, indicating an increase in the hydrophilicity of the surface. It was found that there were no distinct changes in the microstructure or electrical properties of the ITO films with O2 plasma treatment. Synchrotron radiation photoemission spectroscopy data revealed that O2 plasma treatment decreased the amount of carbon contamination and increased the number of unscreened states of In3+ and (O2)2- peroxo species. This played the role of increasing the work function of the ITO films by 1.7 eV. As a result, the turn-on voltage of the OLED decreased markedly from 24 to 8 V and the maximum luminance value of the OLED increased to 2500 cd/m2.

  6. Products and bioenergy from the pyrolysis of rice straw via radio frequency plasma and its kinetics.

    PubMed

    Tu, Wen-Kai; Shie, Je-Lung; Chang, Ching-Yuan; Chang, Chiung-Fen; Lin, Cheng-Fang; Yang, Sen-Yeu; Kuo, Jing T; Shaw, Dai-Gee; You, Yii-Der; Lee, Duu-Jong

    2009-03-01

    The radio frequency plasma pyrolysis technology, which can overcome the disadvantages of common pyrolysis methods such as less gas products while significant tar formation, was used for pyrolyzing the biomass waste of rice straw. The experiments were performed at various plateau temperatures of 740, 813, 843 and 880K with corresponding loading powers of 357, 482, 574 and 664W, respectively. The corresponding yields of gas products (excluding nitrogen) from rice straw are 30.7, 56.6, 62.5 and 66.5wt.% with respect to the original dried sample and the corresponding specific heating values gained from gas products are about 4548, 4284, 4469 and 4438kcalkg(-1), respectively, for the said cases. The corresponding combustible portions remained in the solid residues are about 64.7, 35, 28.2 and 23.5wt.% with specific heating values of 4106, 4438, 4328 and 4251kcalkg(-1) with respective to solid residues, while that in the original dried sample is 87.2wt.% with specific heating value of 4042kcalkg(-1). The results indicated that the amount of combustibles converted into gas products increases with increasing plateau temperature. The kinetic model employed to describe the pyrolytic conversion of rice straw at constant temperatures agrees well with the experimental data. The best curve fittings render the frequency factor of 5759.5s(-1), activation energy of 74.29kJ mol(-1) and reaction order of 0.5. Data and information obtained are useful for the future design and operation of pyrolysis of rice straw via radio frequency plasma.

  7. Plasma production and heating in a tandem mirror central cell by radio-frequency waves in the ion cyclotron frequency range

    NASA Astrophysics Data System (ADS)

    Golovato, S. N.; Brau, K.; Casey, J.; Coleman, J.; Gerver, M. J.; Guss, W.; Hallock, G.; Horne, S.; Irby, J.; Kumazawa, R.; Kesner, J.; Lane, B.; Machuzak, J.; Moran, T.; Myer, R.; Post, R. S.; Sevillano, E.; Smith, D. K.; Sullivan, J. D.; Torti, R.; Wang, L.; Yasaka, Y.; Yao, X. Z.; Zielinski, J.

    1988-12-01

    Plasma production and heating in the central cell of the Tara tandem mirror [Nucl. Fusion 22, 549 (1982); Plasma Physics and Controlled Nuclear Fusion Research, 1986, Proceedings of the 11th International Conference, Kyoto, Japan (IAEA, Vienna, 1987), Vol. 2, p. 251] have been studied. Using radio-frequency excitation by a slot antenna in the ion cyclotron frequency range (ICRF), plasmas with a peak β⊥ of 3%, density of 4×1012 cm-3, ion temperature of 800 eV, and electron temperature of 75-100 eV were routinely produced. The plasma radius decreased with increasing ICRF power, causing reduced ICRF coupling and saturation of the plasma beta. About 70% of the applied ICRF power can be accounted for in direct heating of both ions and electrons. Wave field measurements have identified the applied ICRF to be the slow, ion cyclotron wave. In operation without end plugging, the plasma parameters were limited by poor axial confinement and the requirements for maintenance of magnetohydrodynamic stability and microstability.

  8. A solar plasma stream measured by DRVID and dual-frequency range and Doppler radio metric data

    NASA Technical Reports Server (NTRS)

    Winn, F. B.; Wu, S. C.; Komarek, T. A.; Lam, V. W.; Royden, H. N.; Yip, K. B. W.

    1977-01-01

    S- and X-band DRVID, S- and X-band dual-frequency range (SX(p)), and Doppler (SX(p)) measured a 15-fold increase in the line-of-sight electron content of the solar plasma above the normal plasma background. A general increase in the plasma electron content continued for nearly 50 hours: it started about 12:00 (GMT) on 12 March 1976 and continued to grow until 17:00 (GMT) on 14 March. For the next 55 hours, between 17:00 (GMT) on 14 March to 00:54 (GMT) on 17 March, the plasma level diminished as the background level was approached. Not only were the temporal changes and absolute level of the plasma content measured but the measurements were also used to ascertain the mean-plasma-concentration location: it was estimated to be 4.1 light minutes from earth.

  9. The Effects of Oxygen Plasma on the Chemical Composition and Morphology of the Ru Capping Layer of the Extreme Ultraviolet (EUV) Mask Blanks

    SciTech Connect

    Belau, Leonid; Park, Jeong Y.; Liang, Ted; Somorjai, Gabor A.

    2008-06-07

    Contamination removal from extreme ultraviolet (EUV) mask surfaces is one of the most important aspects to improve reliability for the next generation of EUV lithography. We report chemical and morphological changes of the ruthenium (Ru) mask surface after oxygen plasma treatment using surface sensitive analytical methods: X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and transmission electron microscopy (TEM). Chemical analysis of the EUV masks shows an increase in the subsurface oxygen concentration, Ru oxidation and surface roughness. XPS spectra at various photoelectron takeoff angles suggest that the EUV mask surface was covered with chemisorbed oxygen after oxygen plasma treatment. It is proposed that the Kirkendall effect is the most plausible mechanism that explains the Ru surface oxidation. The etching rate of the Ru capping layer by oxygen plasma was estimated to be 1.5 {+-} 0.2 {angstrom}/min, based on TEM cross sectional analysis.

  10. Modelling algae growth and dissolved oxygen in the Seine River downstream the Paris urban area: contribution of high frequency measurements

    NASA Astrophysics Data System (ADS)

    Vilmin, Lauriane; Escoffier, Nicolas; Groleau, Alexis; Poulin, Michel; Flipo, Nicolas

    2014-05-01

    Dissolved oxygen is a key variable in the hydro-ecological functioning of river systems. The accurate representation of the different biogeochemical processes affecting algal blooms and dissolved oxygen in the water column in hydro-ecological models is crucial for the use of these models as reliable management tools. This study focuses on the water quality of the Seine River along a 225 km stretch, from Paris to the Seine estuary. The study area is highly urbanized and located downstream France's largest agricultural area, and therefore receives large amounts of nutrients. During the last decades, nutrient inputs have been significantly reduced, especially with the implementation of new sewage water treatment technologies. Even though the frequency and the intensity of observed algal blooms have decreased, blooms were observed in 2011 and 2012. These blooms are generally followed by a period of high organic matter accumulation, leading to high mineralization fluxes and potential oxygen depletion. The hydrodynamics and the water quality of the Seine River are simulated for the 2011-2012 period with the distributed process-based hydro-ecological model ProSe (Even et al., 1998). The simulated chlorophyll a and dissolved oxygen concentrations are compared to high frequency measurements at the Bougival monitoring station (50 km downstream from Paris), which is part of the CarboSeine monitoring network. The high frequency continuous dataset allows calibrating of primary producers' physiological parameters. New growth parameters are defined for the diatom community. The blooms occur at the end of the winter period (march 2011 and march 2012) and the optimal temperature for diatom growth is calibrated at 10°C, based on an analysis of the physiological response of the diatom community. One of the main outcomes of the modelling exercise is that the precise identification of the constituting communities of algal blooms must be achieved prior to the modelling itself. With the

  11. Solid-State Radio Frequency Plasma Heating Using a Nonlinear Transmission Line

    NASA Astrophysics Data System (ADS)

    Miller, Kenneth; Ziemba, Timothy; Prager, James; Slobodov, Ilia

    2015-11-01

    Radio Frequency heating systems are rarely used by the small-scale validation platform experiments due to the high cost and complexity of these systems, which typically require high power gyrotrons or klystrons, associated power supplies, waveguides and vacuum systems. The cost and complexity of these systems can potentially be reduced with a nonlinear transmission line (NLTL) based system. In the past, NLTLs have lacked a high voltage driver that could produce long duration high voltage pulses with fast rise times at high pulse repetition frequency. Eagle Harbor Technologies, Inc. (EHT) has created new high voltage nanosecond pulser, which combined with NLTL technology will produce a low-cost, fully solid-state architecture for the generation of the RF frequencies (0.5 to 10 GHz) and peak power levels (~ 10 MW) necessary for plasma heating and diagnostic systems for the validation platform experiments within the fusion science community. The proposed system does not require the use of vacuum tube technology, is inherently lower cost, and is more robust than traditional high power RF heating schemes. Design details and initial bench testing results for the new RF system will be presented. This work is supported under DOE Grant # DE-SC0013747.

  12. Ultrafast modulation of the plasma frequency of vertically aligned indium tin oxide rods.

    PubMed

    Tice, Daniel B; Li, Shi-Qiang; Tagliazucchi, Mario; Buchholz, D Bruce; Weiss, Emily A; Chang, Robert P H

    2014-03-12

    Light-matter interaction at the nanoscale is of particular interest for future photonic integrated circuits and devices with applications ranging from communication to sensing and imaging. In this Letter a combination of transient absorption (TA) and the use of third harmonic generation as a probe (THG-probe) has been adopted to investigate the response of the localized surface plasmon resonances (LSPRs) of vertically aligned indium tin oxide rods (ITORs) upon ultraviolet light (UV) excitation. TA experiments, which are sensitive to the extinction of the LSPR, show a fluence-dependent increase in the frequency and intensity of the LSPR. The THG-probe experiments show a fluence-dependent decrease of the LSPR-enhanced local electric field intensity within the rod, consistent with a shift of the LSPR to higher frequency. The kinetics from both TA and THG-probe experiments are found to be independent of the fluence of the pump. These results indicate that UV excitation modulates the plasma frequency of ITO on the ultrafast time scale by the injection of electrons into, and their subsequent decay from, the conduction band of the rods. Increases to the electron concentration in the conduction band of ∼13% were achieved in these experiments. Computer simulation and modeling have been used throughout the investigation to guide the design of the experiments and to map the electric field distribution around the rods for interpreting far-field measurement results.

  13. Control of Reactive Species Generated by Low-frequency Biased Nanosecond Pulse Discharge in Atmospheric Pressure Plasma Effluent

    NASA Astrophysics Data System (ADS)

    Takashima, Keisuke; Kaneko, Toshiro

    2016-09-01

    The control of hydroxyl radical and the other gas phase species generation in the ejected gas through air plasma (air plasma effluent) has been experimentally studied, which is a key to extend the range of plasma treatment. Nanosecond pulse discharge is known to produce high reduced electric field (E/N) discharge that leads to efficient generation of the reactive species than conventional low frequency discharge, while the charge-voltage cycle in the low frequency discharge is known to be well-controlled. In this study, the nanosecond pulse discharge biased with AC low frequency high voltage is used to take advantages of these discharges, which allows us to modulate the reactive species composition in the air plasma effluent. The utilization of the gas-liquid interface and the liquid phase chemical reactions between the modulated long-lived reactive species delivered from the air plasma effluent could realize efficient liquid phase chemical reactions leading to short-lived reactive species production far from the air plasma, which is crucial for some plasma agricultural applications.

  14. Ionosphere plasma electron parameters from radio frequency sweeping impedance probe measurements

    NASA Astrophysics Data System (ADS)

    Spencer, E.; Patra, S.

    2015-09-01

    In this work we will describe the technique of using an RF sweeping impedance probe (SIP) to measure the AC impedance of an electrically short monopole immersed in a plasma. We analyze the SIP measurements which are taken from the payload of the Storms sounding rocket, launched from Wallops Island, Virginia, in 2007. The scientific objective of the Storms mission was to concentrate on whether density irregularities observed in midlatitude spread F could arise from ionospheric coupling to terrestrial weather. As such, independent measurements of the electron density profile are crucial. Since the inherent nature of the SIP technique makes it relatively insensitive to errors introduced through spacecraft charging, probe contamination, and other DC effects, it is an ideal instrument to employ under disturbed plasma conditions. The instrument measures both the magnitude and phase of the AC impedance from 100 kHz to 20 MHz in 128 frequency steps, performing 45,776 sweeps over the entire flight. From these measurements we infer both the absolute electron density ne and the electron neutral collision frequencies νen throughout the flight trajectory. The SIP data can be approximately analyzed using a fluid formulation and thin sheath approximation particularly at altitudes below 200 km, which allows us to match the measurements to quasi-static analytical formulas. At about 265 km on the upleg, the magnitude data transitioned to a highly damped response with increasing altitude. The phase data, on the other hand, continued to indicate increased plasma density and reduced collisionality as expected. For a large portion of the flight, the payload of the Storms mission exhibited an uncontrolled coning motion, making the local magnetic field orientation with respect to the dipole difficult to decipher. Despite these difficulties, we were able to obtain robust estimates of the electron density profile, using the phase information from each sweep. In addition, the electron

  15. Design of an X-mode swept frequency modulation reflectometer for the measurement of KSTAR plasma density profiles (invited)

    NASA Astrophysics Data System (ADS)

    Roh, Y.; Domier, C. W.; Luhmann, N. C.

    2004-10-01

    An X-mode swept frequency modulation (FM) reflectometry system has been designed to measure the electron density profiles of the "initial" KSTAR plasma. Fast swept HTO oscillators are employed to avoid density