WorldWideScience

Sample records for breakdown

  1. Beauty in the Breakdown

    Science.gov (United States)

    Brisco, Nicole

    2008-01-01

    Most human beings look at erosion as the destruction of a surface, but artists can see that erosion often creates indefinable beauty. Where do you see beauty in the breakdown? In this article, the author presents an innovative lesson that would allow students to observe both human and physical nature. In this activity students will create a work…

  2. Cave breakdown by vadose weathering.

    OpenAIRE

    Osborne R. Armstrong L.

    2002-01-01

    Vadose weathering is a significant mechanism for initiating breakdown in caves. Vadose weathering of ore bodies, mineral veins, palaeokarst deposits, non-carbonate keystones and impure, altered or fractured bedrock, which is intersected by caves, will frequently result in breakdown. Breakdown is an active, ongoing process. Breakdown occurs throughout the vadose zone, and is not restricted to large diameter passages, or to cave ceilings. The surfaces of disarticulated blocks are commonly coate...

  3. Space Charge Modulated Electrical Breakdown.

    Science.gov (United States)

    Li, Shengtao; Zhu, Yuanwei; Min, Daomin; Chen, George

    2016-01-01

    Electrical breakdown is one of the most important physical phenomena in electrical and electronic engineering. Since the early 20(th) century, many theories and models of electrical breakdown have been proposed, but the origin of one key issue, that the explanation for dc breakdown strength being twice or higher than ac breakdown strength in insulating materials, remains unclear. Here, by employing a bipolar charge transport model, we investigate the space charge dynamics in both dc and ac breakdown processes. We demonstrate the differences in charge accumulations under both dc and ac stresses and estimate the breakdown strength, which is modulated by the electric field distortion induced by space charge. It is concluded that dc breakdown initializes in the bulk whereas ac breakdown initializes in the vicinity of the sample-electrode interface. Compared with dc breakdown, the lower breakdown strength under ac stress and the decreasing breakdown strength with an increase in applied frequency, are both attributed to the electric field distortion induced by space charges located in the vicinity of the electrodes. PMID:27599577

  4. PHENIX Work Breakdown Structure

    International Nuclear Information System (INIS)

    The Work Breakdown Structure (WBS) Book begins with this Overview section, which contains the high-level summary cost estimate, the cost profile, and the global construction schedule. The summary cost estimate shows the total US cost and the cost in terms of PHENIX construction funds for building the PHENIX detector. All costs in the WBS book are shown in FY 1993 dollars. Also shown are the institutional and foreign contributions, the level of pre-operations funding, and the cost of deferred items. Pie charts are presented at PHENIX WBS level 1 and 2 that show this information. The PHENIX construction funds are shown broken down to PHENIX WBS level 3 items per fiscal year, and the resulting profile is compared to the RHIC target profile. An accumulated difference of the two profiles is also shown. The PHENIX global construction schedule is presented at the end of the Overview section. Following the Overview are sections for each subsystem. Each subsystem section begins with a summary cost estimate, cost profile, and critical path. The total level 3 cost is broken down into fixed costs (M ampersand S), engineering costs (EDIA) and labor costs. Costs are further broken down in terms of PHENIX construction funds, institutional and foreign contributions, pre-operations funding, and deferred items. Also shown is the contingency at level 3 and the level 4 breakdown of the total cost. The cost profile in fiscal years is shown at level 3. The subsystem summaries are followed by the full cost estimate and schedule sheets for that subsystem. These detailed sheets are typically carried down to level 7 or 8. The cost estimate shows Total, M ampersand S, EDIA, and Labor breakdowns, as well as contingency, for each WBS entry

  5. DC Breakdown experiments for CLIC

    CERN Document Server

    Descoeudres, A; Taborelli, M

    2008-01-01

    For the production of the Compact Linear Collider (CLIC) RF accelerating structures, a material capable of sustaining high electric field, with a low breakdown rate and showing low damages after breakdowns is needed. A DC breakdown study is underway at CERN in order to test candidate materials and surface preparations. The saturated breakdown fields of several metals and alloys have been measured, ranging from 100 MV/m for Al to 850 MV/m for stainless steel, being around 170 MV/m for Cu and 430 MV/m for Mo for example. The conditioning speed of Mo can be significantly improved by removing oxides at the surface with a vacuum heat treatment, typically at 875±C for 2 hours. DC breakdown rate measurements have been done with Cu and Mo electrodes, showing similar results as in RF experiments: the breakdown probability seems to exponentially increase with the applied field. Measurements of time delays before breakdown show two different populations of breakdowns, immediate and delayed breakdowns, indicating that t...

  6. On Preliminary Breakdown

    Science.gov (United States)

    Beasley, W. H.; Petersen, D.

    2013-12-01

    The preliminary breakdown phase of a negative cloud-to-ground lightning flash was observed in detail. Observations were made with a Photron SA1.1 high-speed video camera operating at 9,000 frames per second, fast optical sensors, a flat-plate electric field antenna covering the SLF to MF band, and VHF and UHF radio receivers with bandwidths of 20 MHz. Bright stepwise extensions of a negative leader were observed at an altitude of 8 km during the first few milliseconds of the flash, and were coincident with bipolar electric field pulses called 'characteristic pulses'. The 2-D step lengths of the preliminary processes were in excess of 100 meters, with some 2-D step lengths in excess of 200 meters. Smaller and shorter unipolar electric field pulses were superposed onto the bipolar electric field pulses, and were coincident with VHF and UHF radio pulses. After a few milliseconds, the emerging negative stepped leader system showed a marked decrease in luminosity, step length, and propagation velocity. Details of these events will be discussed, including the possibility that the preliminary breakdown phase consists not of a single developing lightning leader system, but of multiple smaller lightning leader systems that eventually join together into a single system.

  7. Cave breakdown by vadose weathering.

    Directory of Open Access Journals (Sweden)

    Osborne R. Armstrong L.

    2002-01-01

    Full Text Available Vadose weathering is a significant mechanism for initiating breakdown in caves. Vadose weathering of ore bodies, mineral veins, palaeokarst deposits, non-carbonate keystones and impure, altered or fractured bedrock, which is intersected by caves, will frequently result in breakdown. Breakdown is an active, ongoing process. Breakdown occurs throughout the vadose zone, and is not restricted to large diameter passages, or to cave ceilings. The surfaces of disarticulated blocks are commonly coated, rather than having fresh broken faces, and blocks continue to disintegrate after separating from the bedrock. Not only gypsum, but also hydromagnesite and aragonite are responsible for crystal wedging. It is impossible to study or identify potential breakdown foci by surface surveys alone, in-cave observation and mapping are essential.

  8. Breakdown in the pretext tokamak

    International Nuclear Information System (INIS)

    Data are presented on the application of ion cyclotron resonance RF power to preionization in tokamaks. We applied 0.3-3 kW at 12 MHz to hydrogen and obtained a visible discharge, but found no scaling of breakdown voltage with any parameter we were able to vary. A possible explanation for this, which implies that higher RF power would have been much more effective, is discussed. Finally, we present our investigation of the dV/dt dependence of breakdown voltage in PRETEXT, a phenomenon also seen in JFT-2. The breakdown is discussed in terms of the physics of Townsend discharges

  9. Breakdowns in collaborative information seeking

    DEFF Research Database (Denmark)

    Hertzum, Morten

    2010-01-01

    record has introduced risks of new kinds of breakdown in collaborative information seeking. In working to prevent and recover from breakdowns in the seeking and sharing of information a focus on collaborative information seeking will point toward collaborative, organizational, and systemic reasons for......Collaborative information seeking is integral to many professional activities. In hospital work, the medication process encompasses continual seeking for information and collaborative grounding of information. This study investigates breakdowns in collaborative information seeking through analyses...... of the use of the electronic medication record adopted in a Danish healthcare region and of the reports of five years of medication incidents at Danish hospitals. The results show that breakdowns in collaborative information seeking is a major source of medication incidents, that most of these...

  10. RF breakdown by toroidal helicons

    Indian Academy of Sciences (India)

    S K P Tripathi; D Bora; M Mishra

    2001-04-01

    Bounded whistlers are well-known for their efficient plasma production capabilities in thin cylindrical tubes. In this paper we shall present their radio frequency (RF) breakdown and discharge sustaining capabilities in toroidal systems. Pulsed RF power in the electronmagnetohydrodynamic (EMHD) frequency regime is fed to the neutral background medium. After the breakdown stage, discharge is sustained by toroidal bounded whistlers. In these pulsed experiments the behaviour of the time evolution of the discharge could be studied in four distinct phases of RF breakdown, steady state attainment, decay and afterglow. In the steady state average electron density of ≈ 1012 per cc and average electron temperature of ≈ 20 eV are obtained at 10-3 mbar of argon filling pressure. Experimental results on toroidal mode structure, background effects and time evolution of the electron distribution function will be presented and their implications in understanding the breakdown mechanism are discussed.

  11. Analyzing randomly occurring voltage breakdowns

    International Nuclear Information System (INIS)

    During acceptance testing of high-vacuum neutron tubes, 40% of the tubes failed after experiencing high-voltage breakdowns during the aging process. Use of a digitizer in place of an oscilloscope revealed two types of breakdowns, only one of which affected acceptance testing. This information allowed redesign of the aging sequence to prevent tube damage and improve yield and quality of the final product

  12. Breakdown theory for bootstrap quantiles

    OpenAIRE

    Singh, Kesar

    1998-01-01

    A general formula for computing the breakdown point in robustness for the $t$th bootstrap quantile of a statistic $T_n$ is obtained. The answer depends on $t$ and the breakdown point of $T_n$. Since the bootstrap quantiles are vital ingredients of bootstrap confidence intervals, the theory has implications pertaining to robustness of bootstrap confidence intervals. For certain $L$ and $M$ estimators, a robustification of bootstrap is suggested via the notion of Winsorization.

  13. Probabilistic Description of Traffic Breakdowns

    OpenAIRE

    Kuhne, Reinhart; Mahnke, Reinhard; Lubashevsky, Ihor; Kaupuzs, Jevgenijs

    2001-01-01

    We analyze the characteristic features of traffic breakdown. To describe this phenomenon we apply to the probabilistic model regarding the jam emergence as the formation of a large car cluster on highway. In these terms the breakdown occurs through the formation of a certain critical nucleus in the metastable vehicle flow, which enables us to confine ourselves to one cluster model. We assume that, first, the growth of the car cluster is governed by attachment of cars to the cluster whose rate...

  14. Investigations of dc breakdown fields

    CERN Document Server

    Ramsvik, Trond; Reginelli, Alessandra; Taborelli, Mauro

    2006-01-01

    The need for high accelerating gradients for the future 30 GHz multi-TeV e+e- Compact Linear Collider (CLIC) at CERN has triggered a comprehensive study of DC breakdown fields of metals in UHV. The study shows that molybdenum (Mo), tungsten (W), titanium (Ti) and TiVAl reach high breakdown fields, and are thus good candidates for the iris material of CLIC structures. A significant decrease in the saturated breakdown field (Esat) is observed for molybdenum and tungsten when exposed to air. Specifically, at air pressures of 10-5 mbar, the decrease in Esat is found to be 50% and 30% for molybdenum and tungsten, respectively. In addition, a 30% decrease is found when molybdenum is conditioned with a CO pressure of ~1-10-5 mbar. Surface analysis measurements and breakdown conditioning in O2 ambience imply that the origin of the decrease in Esat is closely linked to oxide formation on the cathode surface. "Ex-situ" treatments by ion bombardment of molybdenum effectively reduce the oxide layers, and improve the brea...

  15. Threshold criteria for undervoltage breakdown

    Science.gov (United States)

    Cooley, James E.; Choueiri, Edgar Y.

    2008-05-01

    The conditions under which an externally supplied pulse of electrons will induce breakdown in an undervoltaged, low-gain discharge gap are experimentally and theoretically explored. The minimum number of injected electrons required to achieve breakdown in a parallel-plate gap is measured in argon at pd values of 3-10 Torr m using ultraviolet laser pulses to photoelectrically release electrons from the cathode. This value was found to scale inversely with voltage at constant pd and with pressure within the parameter range explored. A dimensionless theoretical description of the phenomenon is formulated and numerically solved. It is found that a significant fraction of the charge on the plates must be injected for breakdown to be achieved at low gain. It is also found that fewer electrons are required as the gain due to electron-impact ionization (α process) is increased, or as the sensitivity of the α process to electric field is enhanced by increasing the gas pressure. A predicted insensitivity to ion mobility implies that the breakdown is determined during the first electron avalanche when space-charge distortion is greatest.

  16. DC Breakdown Experiments with Iridium Cathode

    CERN Document Server

    Profatilova, Iaroslava; Korsback, Anders; Muranaka, Tomoko; Wuensch, Walter

    2015-01-01

    Electrical breakdown occurring in rf accelerating structures is one of the major disruptions of the accelerated beam in CLIC. At CERN, as complements to rf facilities, DC-spark systems have been used to study breakdown properties of many candidate materials for making rf components. In this note, measurements of conditioning speed, breakdown field and field enhancement factor of iridium are presented comparing with previously tested materials. The average breakdown field after conditioning reached 238 MV/m, which places iridium next to copper. By comparison with results and properties of other metals, the low breakdown field of iridium could be explained by its face-centred-cubic crystal structure.

  17. Protein breakdown in cancer cachexia.

    Science.gov (United States)

    Sandri, Marco

    2016-06-01

    Skeletal muscle is a highly adaptive tissue, capable of altering muscle fiber size, functional capacity and metabolism in response to physiological stimuli. However, pathological conditions such as cancer growth compromise the mechanisms that regulate muscle homeostasis, resulting in loss of muscle mass, functional impairment and compromised metabolism. This tumor-induced condition is characterized by enhanced muscle protein breakdown and amino acids release that sustain liver gluconeogenesis and tissue protein synthesis. Proteolysis is controlled by the two most important cellular degradation systems, the ubiquitin proteasome and autophagy lysosome. These systems are carefully regulated by different signalling pathways that determine protein and organelle turnover. In this review we will describe the involvement of the ubiquitin proteasome and autophagy lysosome systems in cancer cachexia and the principal signalling pathways that regulate tumor-induced protein breakdown in muscle. PMID:26564688

  18. Tune in, breakdown, and reboot

    OpenAIRE

    Pedersen, Michael

    2009-01-01

    Routine work‐process, lack of self‐management, and long work‐hours have traditionally been the main topics of discussion within the occupational stress literature, constituting the primary factors that make people breakdown and burn out. But within the last couple of years, this discussion has expanded its focus from issues concerning the disciplinary work‐space. Increasing attention is now being placed on the problems related to the burgeoning interest in employee empowerme...

  19. Individual breakdown of pension rights

    CERN Multimedia

    2016-01-01

    You should have recently received, via email, your “Individual breakdown of pension rights”.   Please note that: the calculation was based on data as at 1st July 2016, as at 1st September 2016, CERN will introduce a new career structure; the salary position will now be expressed as a percentage of a midpoint of a grade.   We would like to draw your attention to the fact that your pension rights will remain unchanged. Benefits Service CERN Pension Fund

  20. Voltage breakdown on niobium and copper surfaces

    International Nuclear Information System (INIS)

    Experiments have shown that voltage breakdown in superconducting niobium RF cavities is in many ways similar to voltage breakdown on niobium cathodes in DC voltage gaps; most striking are the distinctive starburst patterns and craters that mark the site of voltage breakdown in both superconducting cavities and DC vacuum gaps. Therefore, we can learn much about RF breakdown from simpler, faster DC experiments. We have direct evidence, in the form of before'' and ''after'' pictures, that breakdown events caused by high surface electric fields occur with high probability at contaminant particles on surfaces. Although the pre-breakdown behavior (field emission) seems to depend mostly on the contaminant particles present and little on the substrate, the breakdown event itself is greatly affected by the substrate-niobium, heavily oxidized niobium, electropolished copper, and diamond-machined copper cathodes lead to different kinds of breakdown events. By studying DC voltage breakdown we hope to learn more details about the processes involved in the transition from field emission to catastrophic arcing and the cratering of the surface; as well as learning how to prevent breakdown, we would like to learn how to cause breakdown, which could be important when ''processing'' cavities to reduce field emission. (author)

  1. The Development of Breakdown in Transformer Oil

    Directory of Open Access Journals (Sweden)

    Jozef Kudelcik

    2007-01-01

    Full Text Available The conditions under which breakdown of composite liquid - solid insulation can be occurred, e.g. in transformer, play an important role in designing of such insulation. The initial state of breakdown development is explained based on development of streamers in cavitations. The whole breakdown development in transformer oil is represented by RLC circuit and it depends on the parameters of outer circuit.

  2. On exponential growth [of gas breakdown

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson

    1991-01-01

    The agreement obtained between measured breakdown voltages and predicted breakdown values is frequently used as a means of assessing the validity of the theory/model in question. However, owing to the mathematical nature of exponential growth, it is easy to formulate a criterion that provides acc...... acceptable breakdown values, although the criterion may contain totally unrealistic features. An example from the work of A. Pedersen (1989) showing unrestricted exponential growth in SF 6 is used to highlight the insensitivity of breakdown voltages with respect to modeling...

  3. Work Breakdown Structure (WBS) Handbook

    Science.gov (United States)

    2010-01-01

    The purpose of this document is to provide program/project teams necessary instruction and guidance in the best practices for Work Breakdown Structure (WBS) and WBS dictionary development and use for project implementation and management control. This handbook can be used for all types of NASA projects and work activities including research, development, construction, test and evaluation, and operations. The products of these work efforts may be hardware, software, data, or service elements (alone or in combination). The aim of this document is to assist project teams in the development of effective work breakdown structures that provide a framework of common reference for all project elements. The WBS and WBS dictionary are effective management processes for planning, organizing, and administering NASA programs and projects. The guidance contained in this document is applicable to both in-house, NASA-led effort and contracted effort. It assists management teams from both entities in fulfilling necessary responsibilities for successful accomplishment of project cost, schedule, and technical goals. Benefits resulting from the use of an effective WBS include, but are not limited to: providing a basis for assigned project responsibilities, providing a basis for project schedule development, simplifying a project by dividing the total work scope into manageable units, and providing a common reference for all project communication.

  4. Breakdown of interdependent directed networks.

    Science.gov (United States)

    Liu, Xueming; Stanley, H Eugene; Gao, Jianxi

    2016-02-01

    Increasing evidence shows that real-world systems interact with one another via dependency connectivities. Failing connectivities are the mechanism behind the breakdown of interacting complex systems, e.g., blackouts caused by the interdependence of power grids and communication networks. Previous research analyzing the robustness of interdependent networks has been limited to undirected networks. However, most real-world networks are directed, their in-degrees and out-degrees may be correlated, and they are often coupled to one another as interdependent directed networks. To understand the breakdown and robustness of interdependent directed networks, we develop a theoretical framework based on generating functions and percolation theory. We find that for interdependent Erdős-Rényi networks the directionality within each network increases their vulnerability and exhibits hybrid phase transitions. We also find that the percolation behavior of interdependent directed scale-free networks with and without degree correlations is so complex that two criteria are needed to quantify and compare their robustness: the percolation threshold and the integrated size of the giant component during an entire attack process. Interestingly, we find that the in-degree and out-degree correlations in each network layer increase the robustness of interdependent degree heterogeneous networks that most real networks are, but decrease the robustness of interdependent networks with homogeneous degree distribution and with strong coupling strengths. Moreover, by applying our theoretical analysis to real interdependent international trade networks, we find that the robustness of these real-world systems increases with the in-degree and out-degree correlations, confirming our theoretical analysis. PMID:26787907

  5. Breakdown properties of irradiated MOS capacitors

    International Nuclear Information System (INIS)

    The authors have studied the effects of ionizing and non-ionizing radiation on the breakdown properties of different types of MOS capacitors, with thick (200 nm) and thin (down to 8 nm) oxides. In general, no large variations of the average breakdown field, time-to-breakdown at constant voltage, or charge-to-breakdown at constant voltage, or charge-to-breakdown values have been observed after high dose irradiation (20 Mrad(Si) 9 MeV electrons on thin and thick oxides, 17(Si) Mrad Co60 gamma and 1014 neutrons/cm2 only on thick oxides). However, some modifications of the cumulative failure distributions have been observed in few of the oxides tested

  6. Breakdown characteristics of xenon HID Lamps

    Science.gov (United States)

    Babaeva, Natalia; Sato, Ayumu; Brates, Nanu; Noro, Koji; Kushner, Mark

    2009-10-01

    The breakdown characteristics of mercury free xenon high intensity discharge (HID) lamps exhibit a large statistical time lag often having a large scatter in breakdown voltages. In this paper, we report on results from a computational investigation of the processes which determine the ignition voltages for positive and negative pulses in commercial HID lamps having fill pressures of up to 20 atm. Steep voltage rise results in higher avalanche electron densities and earlier breakdown times. Circuit characteristics also play a role. Large ballast resistors may limit current to the degree that breakdown is quenched. The breakdown voltage critically depends on cathode charge injection by electric field emission (or other mechanisms) which in large part controls the statistical time lag for breakdown. For symmetric lamps, ionization waves (IWs) simultaneously develop from the bottom and top electrodes. Breakdown typically occurs when the top and bottom IWs converge. Condensed salt layers having small conductivities on the inner walls of HID lamps and on the electrodes can influence the ignition behavior. With these layers, IWs tend to propagate along the inner wall and exhibit a different structure depending on the polarity.

  7. Breakdown of Benford's Law for Birth Data

    CERN Document Server

    Ausloos, M; Ileanu, B

    2014-01-01

    Long birth time series for Romania are investigated from Benford's law point of view, distinguishing between families with a religious (Orthodox and Non-Orthodox) affiliation. The data extend from Jan. 01, 1905 till Dec. 31, 2001, i.e. over 97 years or 35 429 days. The results point to a drastic breakdown of Benford's law. Some interpretation is proposed, based on the statistical aspects due to population sizes, rather than on human thought constraints when the law breakdown is usually expected. Benford's law breakdown clearly points to natural causes.

  8. Conditioning and breakdown phenomena in accelerator tubes

    International Nuclear Information System (INIS)

    Important breakdown mechanisms in accelerator tubes are reviewed, and discharge phenomena in NEC tubes are deduced from the surface appearance of the electrodes and insulators of a used tube. Microphotos of these surfaces are shown

  9. Breakdown Point Theory for Implied Probability Bootstrap

    OpenAIRE

    Lorenzo Camponovo; Taisuke Otsu

    2011-01-01

    This paper studies robustness of bootstrap inference methods under moment conditions. In particular, we compare the uniform weight and implied probability bootstraps by analyzing behaviors of the bootstrap quantiles when outliers take arbitrarily large values, and derive the breakdown points for those bootstrap quantiles. The breakdown point properties characterize the situation where the implied probability bootstrap is more robust than the uniform weight bootstrap against outliers. Simulati...

  10. Humidity effects on wire insulation breakdown strength.

    Energy Technology Data Exchange (ETDEWEB)

    Appelhans, Leah

    2013-08-01

    Methods for the testing of the dielectric breakdown strength of insulation on metal wires under variable humidity conditions were developed. Two methods, an ASTM method and the twisted pair method, were compared to determine if the twisted pair method could be used for determination of breakdown strength under variable humidity conditions. It was concluded that, although there were small differences in outcomes between the two testing methods, the non-standard method (twisted pair) would be appropriate to use for further testing of the effects of humidity on breakdown performance. The dielectric breakdown strength of 34G copper wire insulated with double layer Poly-Thermaleze/Polyamide-imide insulation was measured using the twisted pair method under a variety of relative humidity (RH) conditions and exposure times. Humidity at 50% RH and below was not found to affect the dielectric breakdown strength. At 80% RH the dielectric breakdown strength was significantly diminished. No effect for exposure time up to 140 hours was observed at 50 or 80%RH.

  11. Measuring protein breakdown rate in individual proteins in vivo

    DEFF Research Database (Denmark)

    Holm, Lars; Kjaer, Michael

    2010-01-01

    To outline different approaches of how protein breakdown can be quantified and to present a new approach to determine the fractional breakdown rate of individual slow turnover proteins in vivo.......To outline different approaches of how protein breakdown can be quantified and to present a new approach to determine the fractional breakdown rate of individual slow turnover proteins in vivo....

  12. Dielectric breakdown in mineral oil ITO 100 based magnetic fluid

    Science.gov (United States)

    Kudelcik, J.; Bury, P.; Kopcansky, P.; Timko, M.

    The development of dielectric breakdown and the DC dielectric breakdown voltage of magnetic fluids based on inhibited transformer oil ITO 100 were investigated in parallel orientations of external magnetic field. It was shown that the breakdown voltage is strongly influenced by the magnetic nanoparticles. The magnetic fluids with the volume concentration 1and 0.2% had better dielectric properties than pure transformer oil. The increase of breakdown voltage was interpreted on the base of the bubble theory of breakdown.

  13. dc breakdown conditioning and breakdown rate of metals and metallic alloys under ultrahigh vacuum

    CERN Document Server

    Descoeudres, A; Calatroni, S; Taborelli, M; Wuensch, W

    2009-01-01

    RF accelerating structures of the Compact Linear Collider (CLIC) require a material capable of sustaining high electric field with a low breakdown rate and low induced damage. Because of the similarity of many aspects of DC and RF breakdown, a DC breakdown study is underway at CERN in order to test candidate materials and surface preparations, and have a better understanding of the breakdown mechanism under ultra-high vacuum in a simple setup. Conditioning speeds and breakdown fields of several metals and alloys have been measured. The average breakdown field after conditioning ranges from 100 MV/m for Al to 850 MV/m for stainless steel, and is around 170 MV/m for Cu which is the present base-line material for CLIC structures. The results indicate clearly that the breakdown field is limited by the cathode. The presence of a thin cuprous oxide film at the surface of copper electrodes significantly increases the breakdown field. On the other hand, the conditioning speed of Mo is improved by removing oxides at t...

  14. Planned waveguide electric field breakdown studies

    International Nuclear Information System (INIS)

    This paper presents an experimental setup for X-band rf breakdown studies. The setup is composed of a section of WR90 waveguide with a tapered pin located at the middle of the waveguide E-plane. Another pin is used to rf match the waveguide so it operates in a travelling wave mode. By adjusting the penetration depth of the tapered pin, different surface electric field enhancements can be obtained. The setup will be used to study the rf breakdown rate dependence on power flow in the waveguide for a constant maximum surface electric field on the pin. Two groups of pins have been designed. The Q of one group is different and very low. The other has a similar Q. With the test of the two groups of pins, we should be able to discern how the net power flow and Q affect the breakdown. Furthermore, we will apply an electron beam treatment to the pins to study its effect on breakdown. Overall, these experiments should be very helpful in understanding rf breakdown phenomena and could significantly benefit the design of high gradient accelerator structures.

  15. Anticipating electrical breakdown in dielectric elastomer actuators

    Science.gov (United States)

    Muffoletto, Daniel P.; Burke, Kevin M.; Zirnheld, Jennifer L.

    2013-04-01

    The output strain of a dielectric elastomer actuator is directly proportional to the square of its applied electric field. However, since the likelihood of electric breakdown is elevated with an increased applied field, the maximum operating electric field of the dielectric elastomer is significantly derated in systems employing these actuators so that failure due to breakdown remains unlikely even as the material ages. In an effort to ascertain the dielectric strength so that stronger electric fields can be applied, partial discharge testing is used to assess the health of the actuator by detecting the charge that is released when localized instances of breakdown partially bridge the insulator. Pre-stretched and unstretched samples of VHB4910 tape were submerged in dielectric oil to remove external sources of partial discharges during testing, and the partial discharge patterns were recorded just before failure of the dielectric sample.

  16. Analysis of Reciprocity Breakdown in Nonlinear Systems

    International Nuclear Information System (INIS)

    The breakdown of the principle of reciprocity is a well-known phenomenon of nonlinear systems. A structure or system is said to exhibit reciprocity when the response at some point j to an input at some point i is identical to the response at point i when the same input is applied at point j. This paper seeks to explain this phenomenon by adopting a functional series representation which describes the input-output relationship. The frequency-domain Volterra Series representation utilises Higher-Order Frequency Response Functions (HFRFs) (generalisations of the linear FRF) to explain the behaviour of nonlinear systems. This breakdown in reciprocity may be observed through a breakdown in symmetry of HFRFs.

  17. Spectrometers for RF breakdown studies for CLIC

    Science.gov (United States)

    Jacewicz, M.; Ziemann, V.; Ekelöf, T.; Dubrovskiy, A.; Ruber, R.

    2016-08-01

    An e+e- collider of several TeV energy will be needed for the precision studies of any new physics discovered at the LHC collider at CERN. One promising candidate is CLIC, a linear collider which is based on a two-beam acceleration scheme that efficiently solves the problem of power distribution to the acceleration structures. The phenomenon that currently prevents achieving high accelerating gradients in high energy accelerators such as the CLIC is the electrical breakdown at very high electrical field. The ongoing experimental work within the CLIC collaboration is trying to benchmark the theoretical models focusing on the physics of vacuum breakdown which is responsible for the discharges. In order to validate the feasibility of accelerating structures and observe the characteristics of the vacuum discharges and their eroding effects on the structure two dedicated spectrometers are now commissioned at the high-power test-stands at CERN. First, the so called Flashbox has opened up a possibility for non-invasive studies of the emitted breakdown currents during two-beam acceleration experiments. It gives a unique possibility to measure the energy of electrons and ions in combination with the arrival time spectra and to put that in context with accelerated beam, which is not possible at any of the other existing test-stands. The second instrument, a spectrometer for detection of the dark and breakdown currents, is operated at one of the 12 GHz stand-alone test-stands at CERN. Built for high repetition rate operation it can measure the spatial and energy distributions of the electrons emitted from the acceleration structure during a single RF pulse. Two new analysis tools: discharge impedance tracking and tomographic image reconstruction, applied to the data from the spectrometer make possible for the first time to obtain the location of the breakdown inside the structure both in the transversal and longitudinal direction thus giving a more complete picture of the

  18. Linear systems surviving the first breakdown

    International Nuclear Information System (INIS)

    Various types of linear systems are described which are not affected by the first breakdown. They make it possible to operate continuously and are thus very reliable. This is because the first breakdown which occurs affects only very slightly the operation. These components can be replaced during working. The operation, the errors, and the detection are briefly considered in the case of three different designs of linear servo systems. An attempt at comparison is made, it could be developed in a particular case. (author)

  19. Spontaneous symmetry breakdown in gauge theories

    International Nuclear Information System (INIS)

    The dynamical theory of spontaneous breakdown correctly predicts the bound states and relates the order parameters of electron-photon superconductivity and quark-gluon chiral symmetry. A similar statement cannot be made for the standard electro-weak gauge symmetry. (author)

  20. Numerical Borehole Breakdown Investigations using XFEM

    Science.gov (United States)

    Beckhuis, Sven; Leonhart, Dirk; Meschke, Günther

    2016-04-01

    During pressurization of a wellbore a typical downhole pressure record shows the following regimes: first the applied wellbore pressure balances the reservoir pressure, then after the compressive circumferential hole stresses are overcome, tensile stresses are induced on the inside surface of the hole. When the magnitude of these stresses reach the tensile failure stress of the surrounding rock medium, a fracture is initiated and propagates into the reservoir. [1] In standard theories this pressure, the so called breakdown pressure, is the peak pressure in the down-hole pressure record. However experimental investigations [2] show that the breakdown did not occur even if a fracture was initiated at the borehole wall. Drilling muds had the tendency to seal and stabilize fractures and prevent fracture propagation. Also fracture mechanics analysis of breakdown process in mini-frac or leak off tests [3] show that the breakdown pressure could be either equal or larger than the fracture initiation pressure. In order to gain a deeper understanding of the breakdown process in reservoir rock, numerical investigations using the extended finite element method (XFEM) for hydraulic fracturing of porous materials [4] are discussed. The reservoir rock is assumed to be pre-fractured. During pressurization of the borehole, the injection pressure, the pressure distribution and the position of the highest flux along the fracture for different fracturing fluid viscosities are recorded and the influence of the aforementioned values on the stability of fracture propagation is discussed. [1] YEW, C. H. (1997), "Mechanics of Hydraulic Fracturing", Gulf Publishing Company [2] MORITA, N.; BLACK, A. D.; FUH, G.-F. (1996), "Borehole Breakdown Pressure with Drilling Fluids". International Journal of Rock Mechanics and Mining Sciences 33, pp. 39-51 [3] DETOURNAY, E.; CARBONELL, R. (1996), "Fracture Mechanics Analysis of the Breakdown Process in Minifrac or Leakoff Test", Society of Petroleum

  1. Electrical breakdown of carbon nanotube devices and the predictability of breakdown position

    Directory of Open Access Journals (Sweden)

    Gopal Krishna Goswami

    2012-06-01

    Full Text Available We have investigated electrical transport properties of long (>10 μm multiwalled carbon nanotubes (NTs by dividing individuals into several segments of identical length. Each segment has different resistance because of the random distribution of defect density in an NT and is corroborated by Raman studies. Higher is the resistance, lower is the current required to break the segments indicating that breakdown occurs at the highly resistive segment/site and not necessarily at the middle. This is consistent with the one-dimensional thermal transport model. We have demonstrated the healing of defects by annealing at moderate temperatures or by current annealing. To strengthen our mechanism, we have carried out electrical breakdown of nitrogen doped NTs (NNTs with diameter variation from one end to the other. It reveals that the electrical breakdown occurs selectively at the narrower diameter region. Overall, we believe that our results will help to predict the breakdown position of both semiconducting and metallic NTs.

  2. 7 CFR 51.1563 - Soft rot or wet breakdown.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Soft rot or wet breakdown. 51.1563 Section 51.1563... STANDARDS) United States Standards for Grades of Potatoes 1 Definitions § 51.1563 Soft rot or wet breakdown. Soft rot or wet breakdown means any soft, mushy, or leaky condition of the tissue such as slimy...

  3. 7 CFR 51.1582 - Soft rot or wet breakdown.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Soft rot or wet breakdown. 51.1582 Section 51.1582... STANDARDS) United States Consumer Standards for Potatoes Definitions § 51.1582 Soft rot or wet breakdown. Soft rot or wet breakdown means any soft, mushy, or leaky condition of the tissue such as slimy...

  4. Advanced Experimental Techniques for RF and DC Breakdown Research

    CERN Document Server

    Kovermann, J W; Descoeudres, A; Lefèvre, T; Wuensch, W

    2008-01-01

    Advanced experimental techniques are being developed to analyze RF and DC breakdown events. First measurements with a specially built spectrometer have been made with a DC spark setup [1] at CERN and will soon be installed in the CLIC 30GHz accelerating structure test stand to allow comparison between DC and RF breakdown phenomena. This spectrometer is able to measure the light intensity development during a breakdown in narrow wavelength bands in the visible and near infrared range. This will give information about the important aspects of the breakdown including chemical elements, temperature, plasma parameters and possibly precursors of a breakdown.

  5. High-voltage breakdown studies on Si microstrip detectors

    CERN Document Server

    Albergo, S; Azzi, P; Babucci, E; Bacchetta, N; Bader, A J; Bagliesi, G; Basti, A; Biggeri, U; Bilei, G M; Bisello, D; Boemi, D; Bosi, F; Borrello, L; Bozzi, C; Braibant, S; Breuker, Horst; Bruzzi, Mara; Buffini, A; Busoni, S; Calefato, G; Candelori, A; Caner, A; Castaldi, R; Castro, A; Catacchini, E; Checcucci, B; Ciampolini, P; Civinini, C; Creanza, D; D'Alessandro, R; Da Rold, M; Demaria, N; De Palma, M; Dell'Orso, R; Marina, R D; Dutta, S; Eklund, C; Peisert, Anna; Feld, L; Fiore, L; Focardi, E; French, M; Freudenreich, Klaus; Fürtjes, A; Giassi, A; Giorgi, M A; Giraldo, A; Glessing, B; Gu, W H; Hall, G; Hammarström, R; Hebbeker, T; Hrubec, Josef; Muhtinen, M; Kaminski, A; Karimäki, V; Saint-Koenig, M; Krammer, Manfred; Lariccia, P; Lenzi, M; Loreti, M; Lübelsmeyer, K; Lustermann, W; Mättig, P; Maggi, G; Mannelli, M; Mantovani, G C; Marchioro, A; Mariotti, C; Martignon, G; McEvoy, B; Meschini, M; Messineo, A; My, S; Paccagnella, A; Palla, Fabrizio; Pandoulas, D; Papi, A; Parrini, G; Passeri, D; Pieri, M; Piperov, S; Potenza, R; Radicci, V; Raffaelli, F; Raymond, M; Santocchia, A; Schmitt, B; Selvaggi, G; Servoli, L; Sguazzoni, G; Siedling, R; Silvestris, L; Skog, K; Starodumov, Andrei; Stavitski, I; Stefanini, G; Tempesta, P; Tonelli, G; Tricomi, A; Tuuva, T; Vannini, C; Verdini, P G; Viertel, Gert M; Zie, Z; Li Ya Hong; Watts, S; Wittmer, B

    1999-01-01

    The breakdown performance of CMS barrel module prototype detectors and test devices with single and multi-guard structures were studied before and after neutron irradiation up to 2-10/sup 14/ 1 MeV equivalent neutrons. Before irradiation avalanche breakdown occurred at the guard ring implant edges. We measured 100-300 V higher breakdown voltage values for the devices with multi-guard than for devices with single-guard ring, After irradiation and type inversion the breakdown was smoother than before irradiation and the breakdown voltage value increased to 500-600 V for most of the devices. (9 refs).

  6. Breakdown and partial discharges in magnetic liquids.

    Science.gov (United States)

    Herchl, F; Marton, K; Tomčo, L; Kopčanský, P; Timko, M; Koneracká, M; Kolcunová, I

    2008-05-21

    The dielectric properties (permittivity, loss factor, dielectric breakdown strength) of magnetic liquids were investigated. The magnetic liquids were composed of magnetite particles coated with oleic acid as surfactant and dispersed in transformer oil. To determine their dielectric properties they were subjected to a uniform magnetic field at high alternating electric fields up to 14 MV m(-1). Nearly constant permittivity of magnetic liquid with particle volume concentration Φ = 0.0019 as a function of electric field was observed. Magnetic liquids with concentrations Φ = 0.019 and 0.032 showed significant changes of permittivity and loss factor dependent on electric and magnetic fields. The best concentration of magnetic fluid was found at which partial current impulse magnitudes were the lowest. The breakdown strength distribution of the magnetic liquid with Φ = 0.0025 was fitted with the Duxbury-Leath, Weibull and Gauss distribution functions. PMID:21694240

  7. Project management strategies for prototyping breakdowns

    DEFF Research Database (Denmark)

    Granlien, Maren Sander; Pries-Heje, Jan; Baskerville, Richard

    2009-01-01

    , managing the explorative and iterative aspects of prototyping projects is not a trivial task. We examine the managerial challenges in a small scale prototyping project in the Danish healthcare sector where a prototype breakdown and project escalation occurs. From this study we derive a framework of...... strategies for coping with escalation in troubled prototyping projects; the framework is based on project management triangle theory and is useful when considering how to manage prototype breakdown and escalation. All strategies were applied in the project case at different points in time. The strategies led......Prototyping is often presented as a universal solution to many intractable information systems project problems. Prototyping is known to offer at least three advantages (1) provide users with a concrete understanding, (2) eliminate the confusion, (3) cope with uncertainty. On the other hand...

  8. Cooperation Breakdowns under Incomplete Property Rights

    OpenAIRE

    Jean-Pierre Tranchant

    2005-01-01

    In order to analyze conflict and cooperation between a State and a non ruling group in a general equilibrium, I unite pure rent-seeking models and economic models of conflict under an assumption of incomplete property rights. I show that a unique and globally stable Nash equilibrium exists in this game. Cooperation breakdowns appear to be twofold: generalized conflict driven by a collapse of the State and one- sided rebellion due to the coexistence between a strong State and a weak minority. ...

  9. Semantic tags for generative multiview product breakdown

    OpenAIRE

    Paviot, Thomas; Cheutet, Vincent; Lamouri, Samir

    2010-01-01

    The interoperability of IT systems that drive engineering and production processes (i.e. Product Data Management and Enterprise Resource Planning systems) is still an issue. The semantic meaning of product information has to be explicit in order to be able to exchange information between these systems. However, the product breakdown activity generates many disconnected product views over which the product semantics is disseminated and mostly implicit. This paper introduces a methodology allow...

  10. Value Creation using the Mission Breakdown Structure

    OpenAIRE

    Andersen, Erling S.

    2014-01-01

    The modern concept of project success includes the project contributing to the value creation of its base organization. We need tools to discuss what the project itself and the base organization should do to enhance this value creation. The Mission Breakdown Structure tool helps a company set up a project with a clearly defined mission and secures an effective interplay between the base organization and its project. This article presents the tool in principle and use an illustrative real-life...

  11. Comparative Studies of High-Gradient Rf and Dc Breakdowns

    CERN Document Server

    Kovermann, Jan Wilhelm; Wuensch, Walter

    2010-01-01

    The CLIC project is based on normal-conducting high-gradient accelerating structures with an average accelerating gradient of 100 MV/m. The maximum achievable gradient in these structures is limited by the breakdown phenomenon. The physics of breakdowns is not yet fully understood quantitatively. A full knowledge could have strong impact on the design, material choice and construction of rf structures. Therefore, understanding breakdowns has great importance to reaching a gradient of 100MV/m with an acceptable breakdown probability. This thesis addresses the physics underlying the breakdown effect, focusing on a comparison of breakdowns in rf structures and in a dc spark setup. The dc system is simpler, easier to benchmark against simulations, with a faster turnaround time, but the relationship to rf breakdown must be established. To do so, an experimental approach based on optical diagnostics and electrical measurements methods was made. Following an introduction into the CLIC project, a general theoretical ...

  12. Dielectric breakdown of polyimide film in high temperature region

    International Nuclear Information System (INIS)

    The range of temperature was devided into the following three ranges according to the temperature dependence, the dependence on sample thickness and the dependence on the rising ratio of applied electric field of the strength to dielectric breakdown; range I (below the room temperature), II (from the room temperature to 2000C) and III (above 2000C). The dielectric breakdown mechanism in the range I, II and III are the electronic breakdown, the thermal breakdown and the impulse thermal breakdown based on ion conduction, respectively. Although polyimide resin shows mechanically and chemically high heat-resistance, the strength to dielectric breakdown decreases rapidly by the thermal breakdown based on ion conduction at high temperature. For the improvement of the electric features of this resin at high temperature, the supply source of the carrier for ion conduction should be clarified and removed. (Kobatake, H.)

  13. Kinetic Simulations of Dense Plasma Focus Breakdown

    Science.gov (United States)

    Schmidt, A.; Higginson, D. P.; Jiang, S.; Link, A.; Povilus, A.; Sears, J.; Bennett, N.; Rose, D. V.; Welch, D. R.

    2015-11-01

    A dense plasma focus (DPF) device is a type of plasma gun that drives current through a set of coaxial electrodes to assemble gas inside the device and then implode that gas on axis to form a Z-pinch. This implosion drives hydrodynamic and kinetic instabilities that generate strong electric fields, which produces a short intense pulse of x-rays, high-energy (>100 keV) electrons and ions, and (in deuterium gas) neutrons. A strong factor in pinch performance is the initial breakdown and ionization of the gas along the insulator surface separating the two electrodes. The smoothness and isotropy of this ionized sheath are imprinted on the current sheath that travels along the electrodes, thus making it an important portion of the DPF to both understand and optimize. Here we use kinetic simulations in the Particle-in-cell code LSP to model the breakdown. Simulations are initiated with neutral gas and the breakdown modeled self-consistently as driven by a charged capacitor system. We also investigate novel geometries for the insulator and electrodes to attempt to control the electric field profile. The initial ionization fraction of gas is explored computationally to gauge possible advantages of pre-ionization which could be created experimentally via lasers or a glow-discharge. Prepared by LLNL under Contract DE-AC52-07NA27344.

  14. Electromagnetic analysis of breakdown conditions in JET

    Energy Technology Data Exchange (ETDEWEB)

    Maviglia, F., E-mail: francesco.maviglia@unirc.it [Associazione EURATOM-ENEA-CREATE, Univ. di Napoli Federico II, Via Claudio 21, 80125 Napoli (Italy); Albanese, R. [Associazione EURATOM-ENEA-CREATE, Univ. di Napoli Federico II, Via Claudio 21, 80125 Napoli (Italy); Alonso, A. [Asociacion EURATOM-CIEMAT para Fusion, CIEMAT, Madrid (Spain); Lomas, P.J. [CCFE, Culham Science Centre, OX14 3DB Abingdon (United Kingdom)

    2011-10-15

    This paper presents the breakdown studies carried out in the framework of JET Enhancement Projects for Plasma Control Upgrade (PCU) and Enhanced Radial Field Amplifier (ERFA), to obtain plasma formation with different sets of coil turns in the radial field circuit. The electromagnetic conditions to reach the plasma breakdown in the JET machine are strongly dependent on the properties of JET iron core and the effects of the eddy currents driven by the transient electric field on the present passive structures. The study has been carried out by using a linearized dynamic model of JET provided by 2D axisymmetric finite element code CREATE-L [R. Albanese, et al., Nucl. Fusion 38 (1998) 723-738]. The dynamic simulations have been compared with the experimental data. A new fast visible camera has been installed and has been used for the first time at JET for studies of plasma breakdown. The images show, coherently with the model, that the avalanche evolves dynamically towards a region where the stray field is perpendicular to the first wall.

  15. Breakdown localization in the fixed gap system

    CERN Document Server

    Rajamaki, Robin; Wuensch, Walter

    2014-01-01

    Accurate localization of breakdowns in vacuum could help shed light on breakdown related processes that are not yet fully understood. At the DC spark lab at CERN, an instrument called the Fixed Gap System (FGS) has been developed partially for this purpose. Among other things, the FGS has four built-in antennas, which are intended for breakdown localization. The capability of this aspect of the FGS was explored in this report. Specifically, the feasibility of using a method similar to that which is used in cavity Beam Position Monitors (BPMs) was investigated. The usable frequency range of the current experimental setup was also studied. Firstly, a modal analysis of the inner geometry of the FGS was done in HFSS. This showed that the two first modes to be expected in the spark gap quite differ from those of the ideal pillbox – both in field pattern and in frequency ( 4 and 6 GHz vs. 0.2 and 3 GHz). Secondly, S-parameters of the system were measured. These showed that the coupling between antennas is weak...

  16. Runaway breakdown and electrical discharges in thunderstorms

    Science.gov (United States)

    Milikh, Gennady; Roussel-Dupré, Robert

    2010-12-01

    This review considers the precise role played by runaway breakdown (RB) in the initiation and development of lightning discharges. RB remains a fundamental research topic under intense investigation. The question of how lightning is initiated and subsequently evolves in the thunderstorm environment rests in part on a fundamental understanding of RB and cosmic rays and the potential coupling to thermal runaway (as a seed to RB) and conventional breakdown (as a source of thermal runaways). In this paper, we describe the basic mechanism of RB and the conditions required to initiate an observable avalanche. Feedback processes that fundamentally enhance RB are discussed, as are both conventional breakdown and thermal runaway. Observations that provide clear evidence for the presence of energetic particles in thunderstorms/lightning include γ-ray and X-ray flux intensifications over thunderstorms, γ-ray and X-ray bursts in conjunction with stepped leaders, terrestrial γ-ray flashes, and neutron production by lightning. Intense radio impulses termed narrow bipolar pulses (or NBPs) provide indirect evidence for RB particularly when measured in association with cosmic ray showers. Our present understanding of these phenomena and their enduring enigmatic character are touched upon briefly.

  17. RF BREAKDOWN STUDIES USING PRESSURIZED CAVITIES

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Rolland

    2014-09-21

    Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Part of the problem is that RF breakdown in an evacuated cavity involves a complex mixture of effects, which include the geometry, metallurgy, and surface preparation of the accelerating structures and the make-up and pressure of the residual gas in which plasmas form. Studies showed that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas, as needed for muon cooling channels, without the need for long conditioning times, even in the presence of strong external magnetic fields. This positive result was expected because the dense gas can practically eliminate dark currents and multipacting. In this project we used this high pressure technique to suppress effects of residual vacuum and geometry that are found in evacuated cavities in order to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. One of the interesting and useful outcomes of this project was the unanticipated collaborations with LANL and Fermilab that led to new insights as to the operation of evacuated normal-conducting RF cavities in high external magnetic fields. Other accomplishments included: (1) RF breakdown experiments to test the effects of SF6 dopant in H2 and He gases with Sn, Al, and Cu electrodes were carried out in an 805 MHz cavity and compared to calculations and computer simulations. The heavy corrosion caused by the SF6 components led to the suggestion that a small admixture of oxygen, instead of SF6, to the hydrogen would allow the same advantages without the corrosion in a practical muon beam line. (2) A

  18. Femtosecond laser induced breakdown for combustion diagnostics

    International Nuclear Information System (INIS)

    The focused beam of a 100 fs, 800 nm laser is used to induce a spark in some laminar premixed air-methane flames operating with variable fuel content (equivalence ratio). The analysis of the light escaping from the plasma revealed that the Balmer hydrogen lines, Hα and Hβ, and some molecular origin emissions were the most prominent spectral features, while the CN (Β2Σ+-Χ2Σ+) band intensity was found to depend linearly with methane content, suggesting that femtosecond laser induced breakdown spectroscopy can be a useful tool for the in-situ determination and local mapping of fuel content in hydrocarbon-air combustible mixtures.

  19. Need for spontaneous breakdown of chiral symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Salomone, A.; Schechter, J.; Tudron, T.

    1981-07-15

    The question of whether the chiral symmetry of the theory of strong interactions (with massless quarks) is required to be spontaneously broken is examined in the framework of a previously discussed effective Lagrangian for quantum chromodynamics. The assumption that physical masses of the theory be finite leads in a very direct way to the necessity of spontaneous breakdown. This result holds for all N/sub F/> or =2, where N/sub F/ is the number of different flavors of light quarks. The atypical cases N/sub F/ = 1,2 are discussed separately.

  20. QCD emergent from spontaneous breakdown of relativity

    CERN Document Server

    Nishimura, Kimihide

    2016-01-01

    Spontaneous violation of relativistic invariance of the vacuum can derive quantum chromodynamics from an U(1) Higgs model including fermions, if the emergent theory is Lorentz invariant. In this model, the vacuum becomes anisotropic, and a fermion created on a triplet of spin-one vacua acquires degeneracy analogous to the color degrees of freedom. The Nambu-Goldstone bosons originating from the breakdown of rotational symmetry provide the quasi fermions with SU(3)$\\times$U(1) effective interactions, which are interpretable as mediated by gluons and photons. The confinement of quasi quarks as well as that of Nambu-Goldstone gluons follow from the Lorentz invariance of the emergent theory.

  1. Measuring protein breakdown in individual proteins in vivo

    DEFF Research Database (Denmark)

    Holm, Lars; Kjær, Michael

    2010-01-01

    PURPOSE OF REVIEW: To outline different approaches of how protein breakdown can be quantified and to present a new approach to determine the fractional breakdown rate of individual slow turnover proteins in vivo. RECENT FINDINGS: None of the available methods for determining protein breakdown can...... be used to determine the breakdown rate of specific proteins and, therefore, do not keep up to the preceding methodological demands in physiological research. A newly developed approach to determine the fractional breakdown rate of single proteins seems promising. Its conceptual advantage is that the...... proteins of interest are the site of measurement. Hence, the application initially demands the proteins to be labeled with stable isotopically labeled amino acids. Subsequently, the loss of label from the proteins will be dependent on the protein breakdown rate when no labeled amino acids are...

  2. Theoretical studies on secondary breakdowns in a GIS

    Energy Technology Data Exchange (ETDEWEB)

    Rao, M.M.; Naidu, M.S. [Indian Inst. of Science, Bangalore (India). Dept. of High Voltage Engineering; Satyanarayana, S.

    1997-12-31

    The very fast transient overvoltages (VFTO) which are caused by switching operations in a gas-insulated substation (GIS) were discussed. VFTOs can lead to secondary electrical breakdowns within a GIS. The VFTO levels were estimated at different positions in a GIS during different switching operations. It was shown that the VFTO pattern changes after breakdown. The importance of understanding the VFTO level after secondary breakdown in the design of substations was stressed. 6 refs., 8 figs.

  3. Break-down of commercial vanadium pentoxide by alkali solutions

    International Nuclear Information System (INIS)

    Kinetics of the process of commorcial vanadium pentoxide break-down by solutions of sodium hydroxide of different concentration and in different temperature regimes has been studied. The dependence of V2O5 break-down degree on the ratio NaOH:V2O5 is determined and explained. The possibility to use sodium carbonate instead of sodium hydroxide for V2O5 break-down is shown

  4. Measurement of skeletal muscle collagen breakdown by microdialysis

    DEFF Research Database (Denmark)

    Miller, B F; Ellis, D; Robinson, M M;

    2011-01-01

    Exercise increases the synthesis of collagen in the extracellular matrix of skeletal muscle. Breakdown of skeletal muscle collagen has not yet been determined because of technical limitations. The purpose of the present study was to use local sampling to determine skeletal muscle collagen breakdown...... collagen breakdown 17–21 h post-exercise, and our measurement of OHP using GC–MS was in agreement with traditional assays....

  5. Does Competitive Pricing Cause Market Breakdown under Extreme Adverse Selection?

    OpenAIRE

    Mailath, George J.; Georg Noldeke

    2007-01-01

    We study market breakdown in a finance context under extreme adverse selection with and without competitive pricing. Adverse selection is extreme if for any price there are informed agent types with whom uninformed agents prefer not to trade. Market breakdown occurs when no trade is the only equilibrium outcome. We present a necessary and sufficient condition for market breakdown. If the condition holds, then trade is not viable. If the condition fails, then trade can occur under competitive ...

  6. Runaway breakdown and electric discharges in thunderstorms

    International Nuclear Information System (INIS)

    This review concerns the theory of the avalanche multiplication of high-energy (0.1 - 10 MeV) electrons in a neutral material, a newly discovered phenomenon known as runaway breakdown (RB). In atmospheric conditions RB takes place at electric fields an order of magnitude weaker than those needed for normal breakdown in air. Experimental work of the past few years has shown that RB determines the maximum electric field strength in thunderclouds and is behind a variety of phenomena newly observed in thunderstorm atmosphere, such as giant high-altitude discharges between thunderclouds and the ionosphere, anomalous amplifications of X-ray emission, intense bursts of gamma radiation, etc. These phenomena are becoming increasingly active areas of study. A necessary condition for the occurrence of runaway avalanche is the presence of high energy seed electrons. In the atmosphere, these are cosmic ray secondary electrons. Therefore, the observed effects reflect the close relationship between cosmic rays and electrodynamic processes in the thunderstorm atmosphere. The first laboratory results on RB are also presented. Further studies in this area may be of interest for high-current electronics. (reviews of topical problems)

  7. Failure reasons investigations of dumping conveyor breakdown

    Directory of Open Access Journals (Sweden)

    E. Rusiński

    2007-07-01

    Full Text Available Purpose: The main purposes of the paper are to discuss designing and exploitation problems of machines used in strip mines and investigation of its reasons based on steering frame brake-down of the dumping conveyor.Design/methodology/approach: Numerical and experimental approach was used to investigate reasons of the break-down of the dumping conveyor. Numerical simulations based on the finite element method were used. Fractographic and microscopic evaluation and chemical analysis, were used to perform material evaluations. The objectives are achieved by analysis of the numerical simulations results of the broken part of machine and data coming from material evaluations. Based on the mentioned results conclusions concerning results of the failure were given. Additionally the new design of the steering frame half-shafts systems was discussedFindings: The causes of break-down of the steering frame of dumping conveyor were found. Designing and manufacturing problems were the main reasons of the failure. The half shafts systems in undercarriages of the open pit machines are prone to break-downs. They require detailed analysis to be successfully implemented into steering system. Recommendations for the single shaft system are given in the paper.Research limitations/implications: in the half-shaft undercarriage system, the friction in the supporting areas limits horizontal forces acting on safetying. Investigations of the static and sliding friction coefficients should be performed to estimate correct forces and optimal designing rules.Practical implications: The study provides practical implication into designing of half-shafts undercarriage systems and their safetyings. Discussed design of the safetying should be redesigned or the half-shaft system should be changed into one shaft design.Originality/value: The paper provides information backed by evaluation and test results, stating the nexus of causes of the dumping conveyor failure. The

  8. Symmetry breakdown and coupling constants of leptons

    Directory of Open Access Journals (Sweden)

    Gil C. Marques

    2007-06-01

    Full Text Available Based on a new approach to symmetries of the fundamental interactions we deal, in this paper, with the electroweak interactions of leptons. We show that the coupling constants, arising in the way leptons are coupled to intermediate bosons, can be understood as parameters associated to the breakdown of SU(2 and parity symmetries. The breakdown of both symmetries is characterized by a new parameter (the asymetry parameter of the electroweak interactions. This parameter gives a measure of the strength of breakdown of symmetries. We analyse the behaviour of the theory for three values of this parameter. The most relevant value is the one for which only the electromagnetic interactions do not break parity (the maximally allowed left-right asymetric theory. Maximamally allowed parity asymmetry is a requirement that is met for a value of Weinberg's theta-angle that is quite close to the experimental value of this parameter.Com base em uma formulação nova para simetrias das interações fundamentais nós lidamos, neste trabalho, com interações eletrofracas de leptons. Mostramos que as constantes do acoplamento, associadas aos acoplamentos de bósons intermediários, podem ser entendidas como parâmetros associados à quebra de simetrias SU(2 e paridade. A quebra de ambas as simetrias é caracterizada por um parâmetro novo (o parâmetro de assimetria das interações eletrofracas. Este parâmetro dá uma medida da intensidade com que a simetria é quebrada. Analisamos o comportamento da teoria para três valores deste parâmetro. O valor mais relevante é aquele para o qual apenas as interações eletromagnéticas não quebram a paridade (a teoria assimétrica esquerda-direita permitida da maneira máxima. A assimetria máxima permitida é uma exigência que leva a um ângulo de Weinberg cujo valor é próximo daquele observado experimentalmente.

  9. Experimental study of the breakdown phase in coaxial plasma guns

    International Nuclear Information System (INIS)

    The problem of the dielectric breakdown of gases and its relevance in plasma devices is discussed, and preliminary results of an experimental study upon the spatial location and time evolution of the breakdown phase in a plasma focus device are given

  10. 7 CFR 51.1009 - Stylar end breakdown.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Stylar end breakdown. 51.1009 Section 51.1009... STANDARDS) United States Standards for Persian (Tahiti) Limes Definitions § 51.1009 Stylar end breakdown... affected area becomes darker and usually sinks below the healthy surface, but the area remains firm...

  11. Development of Electrical Breakdown in Transformer Oil

    Directory of Open Access Journals (Sweden)

    Jozef Kudelcik

    2006-01-01

    Full Text Available Power transformers are key equipment for transfer and distribution of the electric power. Considering the significance of the power transformers in the electric system, their price and possible damages occurred by accidents, it is necessary to pay attention to their higher prevention. To prevent failure states of transformers, we perform different types ofmeasurements. They shall illustrate a momentary state of the measured equipment and if necessary to draw attention in advance to changes of parameters, which have specific relationship to no-failure operation of the equipment. The conditions under which breakdown of composite liquid/ solid insulation can occur, e.g. in transformer, play an important role in designing such insulation. The liquid, mainly mineral oil, generally constitutes the weakest part of insulation and a great amount of work has been devoted to the study of streamers, which appear in the gaseous phase, and most often are triggering the failure of insulation.

  12. Vortex breakdown in a truncated conical bioreactor

    Science.gov (United States)

    Balci, Adnan; Brøns, Morten; Herrada, Miguel A.; Shtern, Vladimir N.

    2015-12-01

    This numerical study explains the eddy formation and disappearance in a slow steady axisymmetric air-water flow in a vertical truncated conical container, driven by the rotating top disk. Numerous topological metamorphoses occur as the water height, Hw, and the bottom-sidewall angle, α, vary. It is found that the sidewall convergence (divergence) from the top to the bottom stimulates (suppresses) the development of vortex breakdown (VB) in both water and air. At α = 60°, the flow topology changes eighteen times as Hw varies. The changes are due to (a) competing effects of AMF (the air meridional flow) and swirl, which drive meridional motions of opposite directions in water, and (b) feedback of water flow on AMF. For small Hw, the AMF effect dominates. As Hw increases, the swirl effect dominates and causes VB. The water flow feedback produces and modifies air eddies. The results are of fundamental interest and can be relevant for aerial bioreactors.

  13. Study of Bulk and Elementary Screw Dislocation Assisted Reverse Breakdown in Low-Voltage (Dynamic Breakdown Properties. Part 2; Dynamic Breakdown Properties

    Science.gov (United States)

    Neudeck, Philip G.; Fazi, Christian

    1999-01-01

    This paper outlines the dynamic reverse-breakdown characteristics of low-voltage (1 kV) pn junction and Schottky rectifiers, and bipolar gain devices (thyristors, IGBT's, etc.) remains to be investigated.

  14. On the electric breakdown in liquid argon at centimeter scale

    Science.gov (United States)

    Auger, M.; Blatter, A.; Ereditato, A.; Goeldi, D.; Janos, S.; Kreslo, I.; Luethi, M.; von Rohr, C. Rudolf; Strauss, T.; Weber, M. S.

    2016-03-01

    We present a study on the dependence of electric breakdown discharge properties on electrode geometry and the breakdown field in liquid argon near its boiling point. The measurements were performed with a spherical cathode and a planar anode at distances ranging from 0.1 mm to 10.0 mm. A detailed study of the time evolution of the breakdown volt-ampere characteristics was performed for the first time. It revealed a slow streamer development phase in the discharge. The results of a spectroscopic study of the visible light emission of the breakdowns complement the measurements. The light emission from the initial phase of the discharge is attributed to electro-luminescence of liquid argon following a current of drifting electrons. These results contribute to set benchmarks for breakdown-safe design of ionization detectors, such as Liquid Argon Time Projection Chambers (LAr TPC).

  15. Laboratory demonstration of runaway electron breakdown of air

    Energy Technology Data Exchange (ETDEWEB)

    Gurevich, A.V., E-mail: alex@lpi.ru [P.N. Lebedev Physical Institute, RAS, 53 Lenin Avenue, 119991 Moscow (Russian Federation); Mesyats, G.A.; Zybin, K.P. [P.N. Lebedev Physical Institute, RAS, 53 Lenin Avenue, 119991 Moscow (Russian Federation); Reutova, A.G.; Shpak, V.G.; Shunailov, S.A.; Yalandin, M.I. [Institute of Electrophysics, UB RAS, 106 Amundsen Str., 620016 Ekaterinburg (Russian Federation)

    2011-07-18

    Results of experiments demonstrating the phenomenon of runaway electron breakdown of atmospheric air under laboratory conditions are presented. As the discharge-initiating electron beam of duration ∼50 ps had passed through the electrode gap, a runaway electron avalanche current was detected in the electrode gap downstream of the anode grid and then breakdown occurred with picosecond stability. The maximum electron energy and the duration of the avalanche current corresponded to theoretical notions about the runaway electron breakdown of atmospheric air in a strong electric field. Breakdown did not occur at all or was considerably delayed when no initiating beam was used. -- Highlights: → Runaway electron air breakdown in laboratory experiments is demonstrated. → The discharge is initiated by electron beam of 50 ps duration. → The maximum electron energy and avalanche current duration correspond to the theory.

  16. On the Electric Breakdown in Liquid Argon at Centimeter Scale

    CERN Document Server

    Auger, M; Ereditato, A; Goeldi, D; Janos, S; Kreslo, I; Luethi, M; von Rohr, C Rudolf; Strauss, T; Weber, M S

    2015-01-01

    We present a study on the dependence of electric breakdown discharge parameters on electrode geometry and the breakdown field in liquid argon near its boiling point. The measurements were performed with a spherical cathode and a planar anode at distances ranging from 0.1 mm to 10.0 mm. A detailed study of the time evolution of the breakdown volt-ampere characteristics was performed for the first time. It revealed a slow streamer development phase in the discharge. The results of a spectroscopic study of the visible light emission of the breakdowns complement the measurements. The light emission from the initial phase of the discharge is attributed to electro-luminescence of liquid argon following a current of drifting electrons. These results contribute to set benchmarks for breakdown-safe design of ionization detectors, such as Liquid Argon Time Projection Chambers (LAr TPC).

  17. Development of Hybrid Product Breakdown Structure for NASA Ground Systems

    Science.gov (United States)

    Monaghan, Mark W.; Henry, Robert J.

    2013-01-01

    The Product Breakdown Structure is traditionally a method of identification of the products of a project in a tree structure. It is a tool used to assess, plan, document, and display the equipment requirements for a project. It is part of a product based planning technique, and attempts to break down all components of a project in as much detail as possible, so that nothing is overlooked. The PBS for ground systems at the Kennedy Space Center is being developed to encompass the traditional requirements including the alignment of facility, systems, and components to the organizational hierarchy. The Ground Operations Product Breakdown Structure is a hybrid in nature in that some aspects of a work breakdown structure will be incorporated and merged with the Architecture Concept of Operations, Master Subsystem List, customer interface, and assigned management responsibility. The Ground Operations Product Breakdown Structure needs to be able to identify the flexibility of support differing customers (internal and external) usage of ground support equipment within the Kennedy Space Center launch and processing complex. The development of the Product Breakdown Structure is an iterative activity Initially documenting the organization hierarchy structure and relationships. The Product Breakdown Structure identifies the linkage between the customer program requirements, allocation of system resources, development of design goals, and identification logistics products. As the Product Breakdown Structure progresses the incorporation of the results of requirement planning for the customer occurs identifying facility needs and systems. The mature Product Breakdown Structure is baselined with a hierarchical drawing, the Product Breakdown Structure database, and an associated document identifying the verification of the data through the life cycle of the program/product line. This paper will document, demonstrate, and identify key aspects of the life cycle of a Hybrid Product

  18. Experimental Study on High Electrical Breakdown of Water Dielectric

    Institute of Scientific and Technical Information of China (English)

    Zhang Zicheng; Zhang Jiande; Yang Jianhua

    2005-01-01

    By means of a coaxial apparatus, pressurized water breakdown experiments with microsecond charging have been carried out with different surface roughness of electrodes and different ethylene glycol concentrations of ethylene glycol/water mixture. The experimental results about the breakdown stress and the effective time are presented. The breakdown stress is normalized to the situation that the effective time is transformed to 1 μs and analyzed. The conclusions are as follows: (1) the breakdown stress formula is modified to E = 0.561MA-1/10t-1eff/NP1/8; (2)the coefficient M is significantly increased by surface polishing and ethylene glycol additive; (3) it is accumulative for the capacity of improving electrical breakdown strength for surface polishing,ethylene glycol additive, and pressurization, of which pressurization is the most effective method;(4) the highest stress of 235.5 kV/cm is observed in ethylene glycol/water mixture with an ethylene glycol concentration of 80% at a hydrostatic pressure of 1215.9 kPa and is about one time greater than that in pure water at constant pressure; (5) for pressurization and surface pohshing,the primary mechanism to improve the breakdown strength of water dielectric is the increase in the breakdown time delay. Research results indicate great potential in the application of the high power pulse conditioning system of water dielectric.

  19. An energy efficient breakdown cover service for electric cars

    OpenAIRE

    Cappelle, Jan; Vispoel, Stijn; Van Maerhem, Thomas

    2012-01-01

    A typical breakdown cover service unit in Belgium has to assist up to 5 cars a day that end up with an empty fuel tank. As the range of today’s battery electric cars is lower than what people are used to have today, breakdown cover services expect that massive introduction of electric cars will lead to a multiple of EVs ending up with an empty battery. This paper reports about a research project, initiated by a Belgian breakdown cover service, that aimed to design and build a prot...

  20. A STUDY OF HIGH POWER MICROWAVE AIR BREAKDOWN

    Institute of Scientific and Technical Information of China (English)

    LIU GUO-ZHI; LIU JING-YUE; HUANG WEN-HUA; ZHOU JIN-SHAN; SONG XIAO-XIN; NING HUI

    2000-01-01

    This paper presents the results of research on microwave breakdown in air, it includes the experimental study and the theoretical analysis. The experimental study has been done in a waveguide with a frequency of 9.37GHz, the peak power up to 200kW, pulse width from 0.3 to 2.0μs. The repetition rate of microwave source is from single pulse to 970 pulse per second. The process of the breakdown of repetition pulse has also been recorded for a burst of ten pulses. A theoretical model for breakdown threshold is presented also. The theoretical are in good agreement with the experimental ones.

  1. Breakdown voltage analysis of field limiting ring structure

    International Nuclear Information System (INIS)

    In this paper, a computer based analysis is performed to study the effect of floating field-limiting rings (FLR) on the breakdown voltage of Si microstrip detectors. For optimum performance it is crucial to achieve the maximum breakdown voltage for Si detectors operated at very high bias due to extremely hostile radiation environment of LHC. The breakdown performance of Si microstrip detectors can be improved by implementing floating field-limiting rings (FLR) around the active detector area. In the present work, we propose a criterion for optimising the spacing of FLR with respect to the main junction. (author)

  2. Work Breakdown Structures The Foundation for Project Management Excellence

    CERN Document Server

    Norman, Eric S; Fried, Robert T

    2011-01-01

    Understand and apply new concepts regarding Work Breakdown Structures The Work Breakdown Structure (WBS) has emerged as a foundational concept and tool in Project Management. It is an enabler that ensures clear definition and communication of project scope while performing a critical role as a monitoring and controlling tool. Created by the three experts who led the development of PMI's Practice Standard for Work Breakdown Structures, Second Edition, this much-needed text expands on what the standard covers and describes how to go about successfully implementing the WBS within the project life

  3. Electric field breakdown in single molecule junctions.

    Science.gov (United States)

    Li, Haixing; Su, Timothy A; Zhang, Vivian; Steigerwald, Michael L; Nuckolls, Colin; Venkataraman, Latha

    2015-04-22

    Here we study the stability and rupture of molecular junctions under high voltage bias at the single molecule/single bond level using the scanning tunneling microscope-based break-junction technique. We synthesize carbon-, silicon-, and germanium-based molecular wires terminated by aurophilic linker groups and study how the molecular backbone and linker group affect the probability of voltage-induced junction rupture. First, we find that junctions formed with covalent S-Au bonds are robust under high voltage and their rupture does not demonstrate bias dependence within our bias range. In contrast, junctions formed through donor-acceptor bonds rupture more frequently, and their rupture probability demonstrates a strong bias dependence. Moreover, we find that the junction rupture probability increases significantly above ∼1 V in junctions formed from methylthiol-terminated disilanes and digermanes, indicating a voltage-induced rupture of individual Si-Si and Ge-Ge bonds. Finally, we compare the rupture probabilities of the thiol-terminated silane derivatives containing Si-Si, Si-C, and Si-O bonds and find that Si-C backbones have higher probabilities of sustaining the highest voltage. These results establish a new method for studying electric field breakdown phenomena at the single molecule level. PMID:25675085

  4. Novel laser breakdown spectrometer for environmental monitoring

    Science.gov (United States)

    Mirov, Sergey B.; Pitt, Robert E.; Dergachev, Alex Y.; Lee, Wonwoo; Martyshkin, Dmitri V.; Mirov, Olga D.; Randolph, Jeremy J.; DeLucas, Lawrence J.; Brouillette, Christie G.; Basiev, Tasoltan T.; Orlovskii, Yurii V.; Alimov, Olimkhon K.; Vorob'ev, Ivan N.

    1999-11-01

    A novel experimental set-up using laser-induced breakdown spectroscopy (LIBS) for environmental analyses of heavy metals is described in this paper. It is based on state-of-the-art spectroscopic equipment, advanced detectors, and laser atomizers: a 0.75 m spectrometer ARC-750, intensified TE- cooled 256 X 1024 CCD camera, probe with fiber optic guide for signal transportation, and Nd:YAG laser plasma atomizers with two different methods for sample delivery. In the first method the liquid solution containing the atoms to be investigated is drawn into the chamber of the nebulizer. The mixture passes through the nozzle, accompanied by argon gas along with formed aerosol, and enters the plasma plume, which is generated by the laser spark in argon. The second method is based on direct generating of the plasma in the water jet of a continuously circulating sample. LIBS testing of samples containing Al, Cd, Cu, Fe, Pb, Zn, and Cr ions was compared with results using atomic absorption spectrophotometry. Initial indications showed good agreement between these two methods. Detection levels of less than 100 ppb were observed for copper and chromium. The described spectroscopic system exhibits high sensitivity, accumulation of luminescence spectrum in real time; and high dynamic range for concentrations detection from 100 ppb to 1000 ppm.

  5. Medical Applications of Laser Induced Breakdown Spectroscopy

    International Nuclear Information System (INIS)

    Sedentary lifestyle of human beings has resulted in various diseases and in turn we require a potential tool that can be used to address various issues related to human health. Laser Induced Breakdown Spectroscopy (LIBS) is one such potential optical analytical tool that has become quite popular because of its distinctive features that include applicability to any type/phase of samples with almost no sample preparation. Several reports are available that discusses the capabilities of LIBS, suitable for various applications in different branches of science which cannot be addressed by traditional analytical methods but only few reports are available for the medical applications of LIBS. In the present work, LIBS has been implemented to understand the role of various elements in the formation of gallstones (formed under the empyema and mucocele state of gallbladder) samples along with patient history that were collected from Purvancal region of Uttar Pradesh, India. The occurrence statistics of gallstones under the present study reveal higher occurrence of gallstones in female patients. The gallstone occurrence was found more prevalent for those male patients who were having the habit of either tobacco chewing, smoking or drinking alcohols. This work further reports in-situ LIBS study of deciduous tooth and in-vivo LIBS study of human nail

  6. Medical Applications of Laser Induced Breakdown Spectroscopy

    Science.gov (United States)

    Pathak, A. K.; Rai, N. K.; Singh, Ankita; Rai, A. K.; Rai, Pradeep K.; Rai, Pramod K.

    2014-11-01

    Sedentary lifestyle of human beings has resulted in various diseases and in turn we require a potential tool that can be used to address various issues related to human health. Laser Induced Breakdown Spectroscopy (LIBS) is one such potential optical analytical tool that has become quite popular because of its distinctive features that include applicability to any type/phase of samples with almost no sample preparation. Several reports are available that discusses the capabilities of LIBS, suitable for various applications in different branches of science which cannot be addressed by traditional analytical methods but only few reports are available for the medical applications of LIBS. In the present work, LIBS has been implemented to understand the role of various elements in the formation of gallstones (formed under the empyema and mucocele state of gallbladder) samples along with patient history that were collected from Purvancal region of Uttar Pradesh, India. The occurrence statistics of gallstones under the present study reveal higher occurrence of gallstones in female patients. The gallstone occurrence was found more prevalent for those male patients who were having the habit of either tobacco chewing, smoking or drinking alcohols. This work further reports in-situ LIBS study of deciduous tooth and in-vivo LIBS study of human nail.

  7. Avalanche breakdown of the quantum hall effects

    CERN Document Server

    Komiyama, S

    1999-01-01

    Heat stability of two-dimensional electron gas (2DEG) systems in the integer quantum hall effect (IQHE) regime is discussed, and a heat instability is suggested to be the intrinsic mechanism behind the breakdown of the IQHE. Phenomenological argument is provided to suggest that the 2DEG system in the IQHE state becomes thermally unstable when the Hall electric field E sub y reaches a threshold value E sub b. Above E sub b , excited nonequilibrium electrons (holes), which are initially present in the conductor as the temperature fluctuation, are accelerated by E sub y and the 2DEG thereby undergoes a transition to a warm dissipative state. The critical field, E sub b , of this abrupt transition is theoretically estimated and shown to be in fare agreement with experimentally reported values. Consideration of the dynamics of electrons suggests that the transition is a process of avalanche electron-hole pair multiplication, in which a small number of non-equilibrium carriers, gains kinetic energy within a Landau ...

  8. Modeling of a breakdown voltage in microdischarges

    Directory of Open Access Journals (Sweden)

    Đorđević Ivana

    2009-01-01

    Full Text Available Non-equilibrium plasmas have been used as one of the principal technologies for development of microelectronics and they are the basis for the development of new generations of nano-electronics devices required for 65 and 40 nm technologies. Microdischarges recently have become more common in everyday life. Technology of plasma etching has enabled us to develop such discharges and the field of microdischarges has grown into the most interesting field of the physics of collisional non-equilibrium plasmas. Recently, an effort to fabricate microplasma sources that can be integrated with other MEMS devices to form larger Microsystems has been made. Plasma-based microsystems can find application in bio-microelectro- mechanical system (bio-MEMS sterilization, small-scale materials processing and microchemical analysis systems. However, integrability requires not only a size reduction, but also an understanding of the physics governing the new small-scale discharges. In this paper, we have performed modeling of a breakdown voltage by using Particle-in-Cell/Monte Carlo collision (PIC/MCC code taking into account the secondary electron emission due to a high field.

  9. Vortex breakdown in closed containers with polygonal cross sections

    Energy Technology Data Exchange (ETDEWEB)

    Naumov, I. V., E-mail: naumov@itp.nsc.ru; Dvoynishnikov, S. V.; Kabardin, I. K.; Tsoy, M. A. [Kutateladze Institute of Thermophysic SB RAS, Novosibirsk 630090 (Russian Federation)

    2015-12-15

    The vortex breakdown bubble in the confined flow generated by a rotating lid in closed containers with polygonal cross sections was analysed both experimentally and numerically for the height/radius aspect ratio equal to 2. The stagnation point locations of the breakdown bubble emergence and the corresponding Reynolds number were determined experimentally and in addition computed numerically by STAR-CCM+ CFD software for square, pentagonal, hexagonal, and octagonal cross section configurations. The flow pattern and the velocity were observed and measured by combining the seeding particle visualization and the temporal accuracy of laser Doppler anemometry. The vortex breakdown size and position on the container axis were determined for Reynolds numbers, ranging from 1450 to 2400. The obtained results were compared with the flow structure in the closed container of cubical and cylindrical configurations. It is shown that the measured evolution of steady vortex breakdown is in close agreement with the numerical results.

  10. Optimal Rules for Single Machine Scheduling with Stochastic Breakdowns

    Directory of Open Access Journals (Sweden)

    Jinwei Gu

    2014-01-01

    Full Text Available This paper studies the problem of scheduling a set of jobs on a single machine subject to stochastic breakdowns, where jobs have to be restarted if preemptions occur because of breakdowns. The breakdown process of the machine is independent of the jobs processed on the machine. The processing times required to complete the jobs are constants if no breakdown occurs. The machine uptimes are independently and identically distributed (i.i.d. and are subject to a uniform distribution. It is proved that the Longest Processing Time first (LPT rule minimizes the expected makespan. For the large-scale problem, it is also showed that the Shortest Processing Time first (SPT rule is optimal to minimize the expected total completion times of all jobs.

  11. Breakdown processes in wire chambers, prevention and rate capability

    International Nuclear Information System (INIS)

    Breakdowns were optically and electronically observed in drift tubes and drift chambers. They occur at a critical gain for given intensity in a gas mixture when ultraviolet photons are not completely quenched. It was observed that the breakdowns depended critically on average current for a given gas mixture independent of the size of the drift tubes used. Using 4.6% ethyl alcohol vapor mixed into 50/50 argon ethane gas, breakdowns are eliminated up to 7 μA average current drawn by pulses on a 1 cm section of an anode wire under an intense source. Pulses with an avalanche size of 106 electrons, rates above 106 pulses per centimeter per wire may be obtained with the elimination of breakdowns

  12. Breakdown processes in wire chambers, prevention and rate capability

    International Nuclear Information System (INIS)

    Breakdowns were optically and electronically observed in drift tubes and drift chambers. They occur at a critical gain for given intensity in a gas mixture when ultraviolet photons are not completely quenched. It was observed that the breakdowns depended critically on average current for a given gas mixture independent of the size of the drift tubes used. Using 4.6% ethyl alcohol vapor mixed into 50/50 argon ethane gas, breakdowns are eliminated up to 7 μA average current drawn by pulses on a 1 cm section of an anode wire under an intense source. Pulses with an avalanche size of 106 electron rates above 106 pulses per centimeter per wire may be obtained with the elimination of breakdowns

  13. Breakdown processes in wire chambers, prevention and rate capability

    International Nuclear Information System (INIS)

    Breakdowns were optically and electronically observed in drift tubes and drift chambers. They occur at a critical gain for given intensity in a gas mixture when ultraviolet photons are not completely quenched. It was observed that the breakdowns depended critically on average current for a given gas mixture independent of the size of the drift tubes used. Using 4.6% ethyl alcohol vapor mixed into 50/50 argon ethane gas, breakdown are eliminated up to 7 /sub μ/A average current drawn by pulses on a 1 cm section of an anode wire under an intense source. Pulses with an avalanche size of 106 electron rates above 106 pulses per centimeter per wire may be obtained with the elimination of breakdowns

  14. Breakdown analysis for electrodeless discharge in a magnetic field

    International Nuclear Information System (INIS)

    A fluid model for an electrode-less, toroidal breakdown process in presence of a steady magnetic field is developed. Breakdown processes in the Extrap configuration are studied. Both particle balance and energy balance are solved to obtain breakdown voltages. A 2-dimensional particle balance is solved for the Extrap configuration, and the existence of the magnetic nulls seems to play an important role. The concept of the Townsend first coefficient α is found not to be applicable when the particle losses are severe, and the energy balance has to be solved in order to explain the very high low-threshold of the filling pressure observed in the Extrap breakdown experiments. The theoretical results are compared with experiments; a fairly good agreement is achieved. (author)

  15. Breakdown in Breathing: The Complexities of Cystic Fibrosis

    Science.gov (United States)

    ... Subscribe A Breakdown in Breathing The Complexities of Cystic Fibrosis Cystic fibrosis (CF) is an inherited illness that ravages the ... B. Guggino, a researcher with the Johns Hopkins Cystic Fibrosis Center. But in CF, “the mucus gets sticky, ...

  16. Electric field-free gas breakdown in explosively driven generators

    International Nuclear Information System (INIS)

    All known types of gas discharges require an electric field to initiate them. We are reporting on a unique type of gas breakdown in explosively driven generators that does not require an electric field.

  17. Vortex breakdown in closed containers with polygonal cross sections

    International Nuclear Information System (INIS)

    The vortex breakdown bubble in the confined flow generated by a rotating lid in closed containers with polygonal cross sections was analysed both experimentally and numerically for the height/radius aspect ratio equal to 2. The stagnation point locations of the breakdown bubble emergence and the corresponding Reynolds number were determined experimentally and in addition computed numerically by STAR-CCM+ CFD software for square, pentagonal, hexagonal, and octagonal cross section configurations. The flow pattern and the velocity were observed and measured by combining the seeding particle visualization and the temporal accuracy of laser Doppler anemometry. The vortex breakdown size and position on the container axis were determined for Reynolds numbers, ranging from 1450 to 2400. The obtained results were compared with the flow structure in the closed container of cubical and cylindrical configurations. It is shown that the measured evolution of steady vortex breakdown is in close agreement with the numerical results

  18. Controlled breakdown in a coaxial cylinder electrodes ion source

    International Nuclear Information System (INIS)

    The interpretation and prediction of gaseous electrical breakdown characteristics in a coaxial cylinder electrodes ion source are presented. Theoretical analysis for first ionization coefficient in a general form and condition of breakdown in two infinitely long coaxial cylinders are performed. Measurements of plasma density and variation of electric field with axial and radial distances from the source center are given. Experimental determination of minimum breakdown voltage and its corresponding minimum pressure has been used to derive the traditional Townsend gas constant B for both positive and negative corona. Optimum pressure has been found for both positive and negative corona. It has been shown that the breakdown depends on both radii of coaxial cylinder electrodes, rc-ra and rc/ra

  19. Action of space charge on aging and breakdown of polymers

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The study on how space charges affect aging and breakdown of polymers becomes one of the most important domains. Most of the models are based on the injected charges increasing the local field to induce the breakdown of polymers and breaking the large molecule chains. These models ignore the effects of space charge on the microstruc-ture of dielectric materials. In this review, with the calcula-tion of the electromagnetic energy and the electromechanical energy around a trapped charge and with some new experi-mental results, it is proved that aging and breakdown in polymers are caused during the detrapping of the trapped charges. Aging and breakdown of the polymers are related to the release of the electromechanical energy around trapped charges.

  20. Compact High Sensitive Laser-Induced Breakdown Spectroscopy Instrument Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Laser induced breakdown spectroscopy (LIBS) is a versatile tool for in situ substance characterization. Existing LIBS instruments are not compact enough for space...

  1. Surface of Alumina Films after Prolonged Breakdowns in Galvanostatic Anodization

    Directory of Open Access Journals (Sweden)

    Christian Girginov

    2011-01-01

    Full Text Available Breakdown phenomena are investigated at continuous isothermal (20∘C and galvanostatic (0.2–5 mA cm−2 anodizing of aluminum in ammonium salicylate in dimethylformamide (1 M AS/DMF electrolyte. From the kinetic (-curves, the breakdown voltage ( values are estimated, as well as the frequency and amplitude of oscillations of formation voltage ( at different current densities. The surface of the aluminum specimens was studied using atomic force microscopy (AFM. Data on topography and surface roughness parameters of the electrode after electric breakdowns are obtained as a function of anodization time. The electrode surface of anodic films, formed with different current densities until the same charge density has passed (2.5 C cm−2, was assessed. Results are discussed on the basis of perceptions of avalanche mechanism of the breakdown phenomena, due to the injection of electrons and their multiplication in the volume of the film.

  2. Enhancement of dielectric breakdown strengths in polymer film capacitors

    International Nuclear Information System (INIS)

    This paper reports that breakdown voltages of wound, polymer film/metal foil capacitors have been dramatically increased by briefly exposing them (after they had been spirally wound) to a low pressure, low temperature gas plasma. Exposure of wound, polycarbonate-based capacitors to a 96%CF4/4%O2 gas plasma for 4 minutes, for example, produced a 200% increase in breakdown voltage

  3. Ionizing potential waves and high-voltage breakdown streamers.

    Science.gov (United States)

    Albright, N. W.; Tidman, D. A.

    1972-01-01

    The structure of ionizing potential waves driven by a strong electric field in a dense gas is discussed. Negative breakdown waves are found to propagate with a velocity proportional to the electric field normal to the wavefront. This causes a curved ionizing potential wavefront to focus down into a filamentary structure, and may provide the reason why breakdown in dense gases propagates in the form of a narrow leader streamer instead of a broad wavefront.

  4. Gauge Symmetry Breakdown due to Dynamical Higgs Scalar

    CERN Document Server

    Matsuki, T; Haymaker, R W

    2000-01-01

    Assuming dynamical spontaneous breakdown of chiral symmetry for massless gauge theory without scalar fields, we present a method how to construct an effective action of the dynamical Nambu-Goldstone bosons and elemetary fermions by using auxiliary fields. Here dynamical particles are asssumed to be composed of elementary fermions. Various quantities including decay constants are calculated from this effective action. This technique is also applied to gauge symmetry breakdown, $SU(5)\\to SU(4)$, to obtain massive gauge fields.

  5. Dynamical symmetry breakdown in SU(5) and SO(10)

    International Nuclear Information System (INIS)

    Some restrictions imposed upon Grand Unified Theories by dynamical symmetry breakdown are examined. It is observed in particular, that theories with SU(5) as symmetry group, with 3 or more fermion families undergo dynamical symmetry breakdown, and some of the fermions will acquire mass at the Grand Unified scale. On the other hand, the SO(10) group, with 3 families is free from this problem. (Author)

  6. Electric breakdown during the pulsed current spreading in the sand

    Science.gov (United States)

    Vasilyak, L. M.; Vetchinin, S. P.; Panov, V. A.; Pecherkin, V. Ya.; Son, E. E.

    2016-03-01

    Processes of spreading of the pulsed current from spherical electrodes and an electric breakdown in the quartz sand are studied experimentally. When the current density on the electrode exceeds the critical value, a nonlinear reduction occurs in the grounding resistance as a result of sparking in the soil. The critical electric field strengths for ionization and breakdown are determined. The ionization-overheating instability is shown to develop on the electrode, which leads to the current contraction and formation of plasma channels.

  7. Extreme Adverse Selection, Competitive Pricing, and Market Breakdown

    OpenAIRE

    Mailath, George J.; Nöldeke, Georg

    2006-01-01

    Extreme adverse selection arises when private information has unbounded support, and market breakdown occurs when no trade is the only equilibrium outcome. We study extreme adverse selection via the limit behavior of a financial market as the support of private information converges to an unbounded support. A necessary and sufficient condition for market breakdown is obtained. If the condition fails, then there exists competitive market behavior that converges to positive levels of trade when...

  8. Comparative study of experimental signals for multipactor and breakdown.

    CERN Document Server

    Dehler, Micha; Wuensch, Walter; Faus-Golfe, Angeles; Gimeno Martinez, Benito; Kovermann, Jan; Boria, Vicente; Raboso, David

    2012-01-01

    Performance limiting high-power rf phenomenon occur in both transmitter systems in satellites and high-gradient accelerating structures in particle accelerators. In satellites the predominant effect is multipactor while in accelerators it is breakdown. Both communities have studied their respective phenomena extensively and developed particular simulation tools and experimental techniques. A series of experiments to directly compare measurements made under multipactor and breakdown conditions has been initiated with the objective to crosscheck and compare the physics, simulation tools and measurement techniques.

  9. Breakdown of atmospheric pressure microgaps at high excitation frequencies

    International Nuclear Information System (INIS)

    Microwave (mw) breakdown of atmospheric pressure microgaps is studied by a one-dimensional Particle-in-Cell Monte Carlo Collisions numerical model. The effect of both field electron emission and secondary electron emission (due to electron impact, ion impact, and primary electron reflection) from surfaces on the breakdown process is considered. For conditions where field emission is the dominant electron emission mechanism from the electrode surfaces, it is found that the breakdown voltage of mw microdischarge coincides with the breakdown voltage of direct-current (dc) microdischarge. When microdischarge properties are controlled by both field and secondary electron emission, breakdown voltage of mw microdischarge exceeds that of dc microdischarge. When microdischarge is controlled only by secondary electron emission, breakdown voltage of mw microdischarge is smaller than that of dc microdischarge. It is shown that if the interelectrode gap exceeds some critical value, mw microdischarge can be ignited only by electrons initially seeded within the gap volume. In addition, the influence of electron reflection and secondary emission due to electron impact is studied

  10. AVLIS Production Plant work breakdown structure and Dictionary

    Energy Technology Data Exchange (ETDEWEB)

    1984-11-15

    The work breakdown structure has been prepared for the AVLIS Production Plant to define, organize, and identify the work efforts and is summarized in Fig. 1-1 for the top three project levels. The work breakdown structure itself is intended to be the primary organizational tool of the AVLIS Production Plant and is consistent with the overall AVLIS Program Work Breakdown Structure. It is designed to provide a framework for definition and accounting of all of the elements that are required for the eventual design, procurement, and construction of the AVLIS Production Plant. During the present phase of the AVLIS Project, the conceptual engineering phase, the work breakdown structure is intended to be the master structure and project organizer of documents, designs, and cost estimates. As the master project organizer, the key role of the work breakdown structure is to provide the mechanism for developing completeness in AVLIS cost estimates and design development of all hardware and systems. The work breakdown structure provides the framework for tracking, on a one-to-one basis, the component design criteria, systems requirements, design concepts, design drawings, performance projections, and conceptual cost estimates. It also serves as a vehicle for contract reporting. 12 figures, 2 tables.

  11. AVLIS Production Plant work breakdown structure and Dictionary

    International Nuclear Information System (INIS)

    The work breakdown structure has been prepared for the AVLIS Production Plant to define, organize, and identify the work efforts and is summarized in Fig. 1-1 for the top three project levels. The work breakdown structure itself is intended to be the primary organizational tool of the AVLIS Production Plant and is consistent with the overall AVLIS Program Work Breakdown Structure. It is designed to provide a framework for definition and accounting of all of the elements that are required for the eventual design, procurement, and construction of the AVLIS Production Plant. During the present phase of the AVLIS Project, the conceptual engineering phase, the work breakdown structure is intended to be the master structure and project organizer of documents, designs, and cost estimates. As the master project organizer, the key role of the work breakdown structure is to provide the mechanism for developing completeness in AVLIS cost estimates and design development of all hardware and systems. The work breakdown structure provides the framework for tracking, on a one-to-one basis, the component design criteria, systems requirements, design concepts, design drawings, performance projections, and conceptual cost estimates. It also serves as a vehicle for contract reporting. 12 figures, 2 tables

  12. Luminosity of initial breakdown in lightning

    Science.gov (United States)

    Stolzenburg, M.; Marshall, T. C.; Karunarathne, S.; Karunarathna, N.; Vickers, L. E.; Warner, T. A.; Orville, R. E.; Betz, H.-D.

    2013-04-01

    Time correlated high-speed video and electromagnetic data for 15 cloud-to-ground and intracloud lightning flashes reveal bursts of light, bright enough to be seen through intervening cloud, during the initial breakdown (IB) stage and within the first 3 ms after flash initiation. Each sudden increase in luminosity is coincident with a CG type (12 cases) or an IC type (3 cases) IB pulse in fast electric field change records. The E-change data for 217 flashes indicate that all CG and IC flashes have IB pulses. The luminosity bursts of 14 negative CG flashes occur 11-340 ms before the first return stroke, at altitudes of 4-8 km, and at 4-41 km range from the camera. In seven cases, linear segments visibly advance away from the first light burst for 55-200 µs, then the entire length dims, then the luminosity sequence repeats along the same path. These visible initial leaders or streamers lengthen intermittently to about 300-1500 m. Their estimated 2-D speeds are 4-18 × 105 m s-1 over the first few hundred microseconds and decrease by about 50% over the first 2 ms. In other cases, only a bright spot or a broad area of diffuse light, presumably scattered by intervening cloud, is visible. The bright area grows larger over 20-60 µs before the luminosity fades in about 100 µs, then this sequence may repeat several times. In several flashes, a 1-2 ms period of little or no luminosity and small E-change is observed following the IB stage prior to stepped leader development.

  13. Influence of ambient gases on the dc saturated breakdown field of molybdenum, tungsten, and copper during intense breakdown conditioning

    CERN Document Server

    Ramsvik, T; Reginelli, A; Taborelli, M

    2007-01-01

    A comprehensive investigation of the effect of Ar, H2, air, and CO on the saturated breakdown field (Esat) of molybdenum, tungsten, and copper has been performed at intensive breakdown conditioning. A significant decrease in Esat is observed for molybdenum and tungsten when exposed to air. Specifically, at air pressures of ∼10-5   mbar, the decrease in Esat is found to be up to 50% and ∼30% compared to UHV conditions for molybdenum and tungsten, respectively. In addition, a ∼30% decrease is found when molybdenum is conditioned with a ∼10-5   mbar CO pressure. Surface analysis measurements and breakdown conditioning in O2 ambience imply that the origin of the decrease in Esat is closely linked to oxide formation on the electrode surfaces. Ex situ heat treatment of molybdenum is shown to improve the breakdown characteristics drastically.

  14. Avalanche electron bunching in a Corbino disk in the quantum Hall effect breakdown regime

    Science.gov (United States)

    Chida, Kensaku; Hata, Tokuro; Arakawa, Tomonori; Matsuo, Sadashige; Nishihara, Yoshitaka; Tanaka, Takahiro; Ono, Teruo; Kobayashi, Kensuke

    2014-06-01

    We have measured the current noise in a device with Corbino geometry to investigate the dynamics of electrons in the breakdown regime of the integer quantum Hall effect (QHE). In the breakdown regime, the Fano factor of the current noise exceeds 103, which indicates the presence of electron bunching. As super-Poissonian current noise is observed only in the breakdown regime, the bunching effect is related to the QHE breakdown. These observations support a QHE breakdown mechanism that involves an electron avalanche.

  15. Abnormal breakdown characteristic in a two-phase mixture

    International Nuclear Information System (INIS)

    A two-phase mixture (TPM) is a mixture of gas and macroparticles of high concentration. Based on Townsend's theory, a new cell-iterative model in analytical form for the breakdown mechanism in TPM is presented. Compared with the original cell-iterative model in our previous paper, the obstructive factor of the macroparticles that influences the electron avalanche propagation is considered, except for the macroparticles distorting the electrical field and capture of the electrons. The cell attractive parameter k is presented according to the classical continuum theory for field charging. The modified Paschen law for a TPM is presented to calculate the breakdown voltage. The breakdown voltage of the TPM, UTPM, increases gradually with an increase in the macroparticle number density (m). The voltage UTPM is lower than that of the pure gas at low m values and larger at high m values. With a decrease of the macroparticle volume fraction and the dielectric mismatch, the voltage UTPM increases gradually at low m values and decreases gradually at high m values. The voltage UTPM at pd 200 cm Torr is lower than that at pd = 760 cm Torr for low m values and larger for high m values. This kind of abnormal breakdown characteristic in the TPM occurs in the case of high macroparticle volume fraction. On the other hand, the minimum of the TPM's Paschen curve increases with increase in m. It provides the possibility and the conditions of greatly increasing the breakdown voltage in a nearly uniform field

  16. Laser-induced breakdown spectroscopy analysis of asbestos

    International Nuclear Information System (INIS)

    Laser-induced breakdown spectroscopy was applied to test the possibility of detecting and identifying asbestos in different samples in view of the perspective at field operation without sample preparation which is peculiar to this technique. Several like-resin materials were first investigated by laser-induced breakdown spectroscopy, in order to find an asbestos container assuring safe laboratory operation during the material characterization aimed to identify indicators suitable for a quick identification on field. Successively, spectra of asbestos samples of both in serpentine and amphibole forms were measured and the variability in elemental composition was calculated from the emission spectra. Ratios of intensities of characteristic elements were tested as indicators for asbestos recognition. Laser-induced breakdown spectroscopy results were compared with those obtained by analyzing the same asbestos samples with a scanning electron microscopy equipped with an energy dispersive X-ray spectroscopy, a good correlation was found for Mg/Si and Fe/Si, thus showing the capability of laser-induced breakdown spectroscopy as a diagnostic tool for this category of materials. In particular, it was demonstrated that the method based on two indicators derived from laser-induced breakdown spectroscopy intensity ratios allows to discriminate between asbestos and cements in single shot measurements suitable to field operation

  17. Breakdown resistance of refractory metals compared to copper

    CERN Document Server

    Taborelli, M; Kildemo, M

    2004-01-01

    The behaviour of Mo, W and Cu with respect to electrical breakdown in ultra high vacuum has been investigated by means of a capacitor discharge method. The maximum stable electric field without breakdown and the field enhancement factor, beta have been measured between electrodes of the same material in a sphere/plane geometry for anode and cathode, respectively. The maximum stable field increases as a function of the number of breakdown events for W and Mo. In contrast, no systematic increase is observed for Cu. The highest values obtained are typically 500 MV/m for W, 350 MV/m for Mo and only 180 MV/m for Cu. This conditioning, found for the refractory metals, corresponds to a simultaneous decrease of beta and is therefore related to the field emission properties of the surface and their modification upon sparking. Accordingly, high beta values and no applicable field increase occur for Cu even after repeated breakdown. The results are compared with RF breakdown experiments [1] performed on prototype 30 GHz...

  18. Investigation of mechanism of breakdown in XLPE cables. Final report

    Energy Technology Data Exchange (ETDEWEB)

    McKean, A.L.

    1976-07-01

    The basic hypothesis that microporosity plays a significant role in the mechanism of breakdown of XLPE cable is explored. The potential improvement achieved by impregnating the microporous regions of the cable core with a neutral liquid is evaluated, with relation to ac voltage life and impulse strength. The effect at higher frequency is also demonstrated. A similar test program is pursued on model cables, designed to explore the effects of gas pressure and gas type on breakdown and life, since it is reasonable to expect that only the microporous regions of the insulation should be sensitive to the gas-pressure environment. Comparison of gas-pressurized model breakdown stress (and related microvoid size) with basic Paschen curves demonstrates reasonably good agreement, indicating that partial discharge is the basic mechanism of fatigue and breakdown. The form of the voltage life curve above and below the discharge inception level is proposed, and evidence is presented indicating breakdown originates in the bulk insulation as well as at the shield interface. It is also shown that model cable discharge energies are below 0.1 pC, even at very high stress, and cannot be measured with modern detectors. Results with liquid or gas impregnation suggest a possible approach to dielectric improvement.

  19. Study of the breakdown voltage of SiPMs

    CERN Document Server

    Chmill, V; Klanner, R; Nitschke, M; Schwandt, J

    2016-01-01

    The breakdown behaviour of SiPMs (Silicon PhotoMultiplier) with pixel sizes of 15$\\times $15, 25$\\times $25, 50$\\times $50, and 100$\\times $100 $\\mu $m$^2$, manufactured by KETEK, has been investigated. From the current-voltage characteristics measured with and without illumination by LED light of 470 nm wavelength, the current-breakdown voltage, $V_I$, and from linear fits of the voltage dependence of the SiPM gain, measured by recording pulse-area spectra, the gain-breakdown voltage, $V_G$, have been obtained. The voltage dependence of the Geiger-breakdown probability was determined from the fraction of zero photoelectron events with LED illumination. By comparing the results to a model calculation, the photodetection-breakdown voltage, $V_{PD}$, has been determined. Within experimental uncertainties, $V_I$ and $V_{PD}$ are equal and independent of pixel size. For $V_G$, a dependence on pixel size is observed. The difference $V_I - V_G$ is about 1 V for the SiPM with 15 $\\mu $m pixels, decreases with pixel ...

  20. 42GHz ECRH assisted Plasma Breakdown in tokamak SST-1

    Directory of Open Access Journals (Sweden)

    Shukla B. K.

    2015-01-01

    Full Text Available In SST-1, 42GHz ECRH system has been commissioned to carry out breakdown and heating experiments at 0.75T and 1.5T operating toroidal magnetic fields. The 42GHz ECRH system consists of high power microwave source Gyrotron capable to deliver 500kW microwave power for 500ms duration, approximately 20 meter long transmission line and a mirror based launcher. The ECRH power in fundamental O-mode & second harmonic X-mode is launched from low field side (radial port of the tokamak. At 0.75T operation, approximately 300 kW ECH power is launched in second harmonic X-mode and successful ECRH assisted breakdown is achieved at low loop_voltage ~ 3V. The ECRH power is launched around 45ms prior to loop voltage. The hydrogen pressure in tokamak is maintained ~ 1×10-5mbar and the pre-ionized density is ~ 4×1012/cc. At 1.5T operating toroidal magnetic field, the ECH power is launched in fundamental O-mode. The ECH power at fundamental harmonic is varied from 100 kW to 250 kW and successful breakdown is achieved in all ECRH shots. In fundamental harmonic there is no delay in breakdown while at second harmonic ~ 40ms delay is observed, which is normal in case of second harmonic ECRH assisted breakdown.

  1. Accoustic Localization of Breakdown in Radio Frequency Accelerating Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Lane, Peter Gwin [IIT, Chicago

    2016-07-01

    Current designs for muon accelerators require high-gradient radio frequency (RF) cavities to be placed in solenoidal magnetic fields. These fields help contain and efficiently reduce the phase space volume of source muons in order to create a usable muon beam for collider and neutrino experiments. In this context and in general, the use of RF cavities in strong magnetic fields has its challenges. It has been found that placing normal conducting RF cavities in strong magnetic fields reduces the threshold at which RF cavity breakdown occurs. To aid the effort to study RF cavity breakdown in magnetic fields, it would be helpful to have a diagnostic tool which can localize the source of breakdown sparks inside the cavity. These sparks generate thermal shocks to small regions of the inner cavity wall that can be detected and localized using microphones attached to the outer cavity surface. Details on RF cavity sound sources as well as the hardware, software, and algorithms used to localize the source of sound emitted from breakdown thermal shocks are presented. In addition, results from simulations and experiments on three RF cavities, namely the Aluminum Mock Cavity, the High-Pressure Cavity, and the Modular Cavity, are also given. These results demonstrate the validity and effectiveness of the described technique for acoustic localization of breakdown.

  2. Surface Breakdown Characteristics of Silicone Oil for Electric Power Apparatus

    Science.gov (United States)

    Wada, Junichi; Nakajima, Akitoshi; Miyahara, Hideyuki; Takuma, Tadasu; Okabe, Shigemitu; Kohtoh, Masanori; Yanabu, Satoru

    This paper describes the surface breakdown characteristics of the silicone oil which has the possibility of the application to innovative switchgear as an insulating medium. At the first step, we have experimentally studied on the impulse breakdown characteristics of the configuration with a triple-junction where a solid insulator is in contact with the electrode. The test configurations consist of solid material (Nomex and pressboard) and liquid insulation oil (silicone and mineral oil). We have discussed the experimental results based on the maximal electric field at a triple-junction. As the second step, we have studied the configuration which may improve the surface breakdown characteristics by lowering the electric field near the triple-junction.

  3. RF Breakdown in Normal Conducting Single-cell Structures

    CERN Document Server

    Dolgashev, Valery A; Higo, Toshiyasu; Nantista, Christopher D; Tantawi, Sami G

    2005-01-01

    Operating accelerating gradient in normal conducting accelerating structures is often limited by rf breakdown. The limit depends on multiple parameters, including input rf power, rf circuit, cavity shape and material. Experimental and theoretical study of the effects of these parameters on the breakdown limit in full scale structures is difficult and costly. We use 11.4 GHz single-cell traveling wave and standing wave accelerating structures for experiments and modeling of rf breakdown behavior. These test structures are designed so that the electromagnetic fields in one cell mimic the fields in prototype multicell structures for the X-band linear collider. Fields elsewhere in the test structures are significantly lower than that of the single cell. The setup uses matched mode converters that launch the circular TM01 mode into short test structures. The test structures are connected to the mode launchers with vacuum rf flanges. This setup allows economic testing of different cell geometries, cell materials an...

  4. Electron cyclotron resonance breakdown studies in a linear plasma system

    Indian Academy of Sciences (India)

    Vipin K Yadav; K Sathyanarayana; D Bora

    2008-03-01

    Electron cyclotron resonance (ECR) plasma breakdown is studied in a small linear cylindrical system with four different gases - hydrogen, helium, argon and nitrogen. Microwave power in the experimental system is delivered by a magnetron at 2.45 ± 0.02 GHz in TE10 mode and launched radially to have extra-ordinary (X) wave in plasma. The axial magnetic field required for ECR in the system is such that the fundamental ECR surface ( = 875.0 G) resides at the geometrical centre of the plasma system. ECR breakdown parameters such as plasma delay time and plasma decay time from plasma density measurements are carried out at the centre using a Langmuir probe. The operating parameters such as working gas pressure (1 × 10-5 -1 × 10-2 mbar) and input microwave power (160{800 W) are varied and the corresponding effect on the breakdown parameters is studied. The experimental results obtained are presented in this paper.

  5. Electrical breakdown gas detector featuring carbon nanotube array electrodes.

    Science.gov (United States)

    Kim, Seongyul; Pal, Sunil; Ajayan, Pulickel M; Borca-Tasciuc, Theodorian; Koratkar, Nikhil

    2008-01-01

    We demonstrate here detection of dichloro-difluoro-methane and oxygen in mixtures with helium using a carbon nanotube electrical breakdown sensor device. The sensor is comprised of an aligned array of multiwalled carbon nanotubes deposited on a nickel based super-alloy (Inconel 600) as the anode; the counter electrode is a planar nickel sheet. By monitoring the electrical breakdown characteristics of oxygen and dichloro-difluoro-methane in a background of helium, we find that the detection limit for dichloro-difluoro-methane is approximately 0.1% and the corresponding limit for oxygen is approximately 1%. A phenomenologigal model is proposed to describe the trends observed in detection of the two mixtures. These results indicate that carbon nanotube based electrical breakdown sensors show potential as end detectors in gas-chromatography devices. PMID:18468093

  6. High-voltage atmospheric breakdown across intervening rutile dielectrics.

    Energy Technology Data Exchange (ETDEWEB)

    Williamson, Kenneth Martin; Simpson, Sean; Coats, Rebecca Sue; Jorgenson, Roy Eberhardt; Hjalmarson, Harold Paul; Pasik, Michael Francis

    2013-09-01

    This report documents work conducted in FY13 on electrical discharge experiments performed to develop predictive computational models of the fundamental processes of surface breakdown in the vicinity of high-permittivity material interfaces. Further, experiments were conducted to determine if free carrier electrons could be excited into the conduction band thus lowering the effective breakdown voltage when UV photons (4.66 eV) from a high energy pulsed laser were incident on the rutile sample. This report documents the numerical approach, the experimental setup, and summarizes the data and simulations. Lastly, it describes the path forward and challenges that must be overcome in order to improve future experiments for characterizing the breakdown behavior for rutile.

  7. Exploration of Underwater Laser Breakdown Using Two Synchronized Gated Cameras

    Science.gov (United States)

    Huwel, Lutz; Baumgart, Clayton; Betts, Susannah; Morgan, Thomas J.; Graham, William G.

    2014-10-01

    Using two synchronized intensified CCD cameras, we have studied spatial and temporal characteristics of optical breakdown in water created by a focused 10 ns pulsed Nd:YAG laser operating at 1064 nm. For three water samples with different impurity content (ultrapure, distilled, and tap water), the plasma evolution was monitored up to 1 ms after breakdown. Images taken by the two cameras, systematically delayed relative to each other, reveal that the center of emission intensity does not remain at a fixed location. In single plasma events, the center first moves, on average, toward the incoming laser beam. Then, at about 100 to 200 ns, the apparent direction of motion reverses and the center returns towards the focal point. On the other hand, in repetitive breakdown the time averaged center moves steadily downstream with each subsequent pulse. Details of this behavior depend on repetition frequency. We will also present shadowgraphy results revealing time resolved speeds of both shockwave and bubble expansion.

  8. Fundamentals of undervoltage breakdown through the Townsend mechanism

    Science.gov (United States)

    Cooley, James E.

    The conditions under which an externally supplied pulse of electrons will induce breakdown in an undervoltaged, low-gain, DC discharge gap are experimentally and theoretically explored. The phenomenon is relevant to fundamental understanding of breakdown physics, to switching applications such as triggered spark gaps and discharge initiation in pulsed-plasma thrusters, and to gas-avalanche particle counters. A dimensionless theoretical description of the phenomenon is formulated and solved numerically. It is found that a significant fraction of the charge on the plates must be injected for breakdown to be achieved at low avalanche-ionization gain, when an electron undergoes fewer than approximately 10 ionizing collisions during one gap transit. It is also found that fewer injected electrons are required as the gain due to electron-impact ionization (alpha process) is increased, or as the sensitivity of the alpha process to electric field is enhanced by decreasing the reduced electric field (electric field divided by pressure, E/p). A predicted insensitivity to ion mobility implies that breakdown is determined during the first electron avalanche when space charge distortion is greatest. A dimensionless, theoretical study of the development of this avalanche reveals a critical value of the reduced electric field to be the value at the Paschen curve minimum divided by 1.6. Below this value, the net result of the electric field distortion is to increase ionization for subsequent avalanches, making undervoltage breakdown possible. Above this value, ionization for subsequent avalanches will be suppressed and undervoltage breakdown is not possible. Using an experimental apparatus in which ultraviolet laser pulses are directed onto a photo-emissive cathode of a parallel-plate discharge gap, it is found that undervoltage breakdown can occur through a Townsend-like mechanism through the buildup of successively larger avalanche generations. The minimum number of injected

  9. Effects of fluid penetration on breakdown pressures in hydraulic fracturing tectonic stress measurements and estimation of breakdown pressures

    International Nuclear Information System (INIS)

    A new method is proposed for the estimation of the so-called breakdown pressure in the hydraulic fracturing tectonic stress measurements. The stress field around the well bore was analyzed taking into account the influence of the fluid penetration into the porous rock due to the pressurization of the well bore. By the use of the stress field, the breakdown pressure, i.e., the well bore pressure required to induce cracks on the well bore was estimated based on a newly constructed fracture criterion. The criterion determines the breakdown pressure as a pressure value at which the maximum tensile effective stress at a characteristic depth beyond the well bore surface, reaches the tensile strength of the rock. To verify the new method, laboratory hydraulic fracturing experiments were conducted on cubical rock specimens under uniaxial compression. Results show that the breakdown pressures predicted by the classical method are erroneously lower than the experimental data when the uniaxial compressive stress is large. On the other hand, the breakdown pressures predicted by the present method perfectly agree with the experimental data independent of the magnitude of the uniaxial compressive stress. (author)

  10. New phenomenology of gas breakdown in DC and RF fields

    International Nuclear Information System (INIS)

    This paper follows a review lecture on the new developments in the field of gas breakdown and low current discharges, usually covered by a form of Townsend's theory and phenomenology. It gives an overview of a new approach to identifying which feedback agents provide breakdown, how to model gas discharge conditions and reconcile the results with binary experiments and how to employ that knowledge in modelling gas discharges. The next step is an illustration on how to record volt-ampere characteristics and use them on one hand to obtain the breakdown voltage and, on the other, to identify the regime of operation and model the secondary electron yields. The second aspect of this section concerns understanding the different regimes, their anatomy, how those are generated and how free running oscillations occur. While temporal development is the most useful and interesting part of the new developments, the difficulty of presenting the data in a written form precludes an easy publication and discussion. Thus, we shall only mention some of the results that stem from these measurements. Most micro discharges operate in DC albeit with complex geometries. Thus, parallel plate micro discharge measurements were needed to establish that Townsend's theory, with all its recent extensions, is still valid until some very small gaps. We have shown, for example, how a long-path breakdown puts in jeopardy many experimental observations and why a flat left-hand side of the Paschen curve often does not represent good physics. We will also summarize a kinetic representation of the RF breakdown revealing a somewhat more complex picture than the standard model. Finally, we will address briefly the breakdown in radially inhomogeneous conditions and how that affects the measured properties of the discharge. This review has the goal of summarizing (rather than developing details of) the current status of the low-current DC discharges formation and operation as a discipline which

  11. Breakdown and field emission conditioning of Cu, Mo and W

    CERN Document Server

    Taborelli, M; Calatroni, S

    2004-01-01

    The ultra-high-vacuum electrical breakdown characteristics of copper, molybdenum and tungsten have been explored in a setup based on a capacitor discharge. Upon repeated sparking, tungsten and molybdenum showed improvement of the maximum applicable field before breakdown (conditioning) in contrast to copper, which experienced alternate improvement and degrading. After conditioning, tungsten withstood the highest applied field followed by molybdenum and copper. This behaviour was correlated with that of the field enhancement factor  extracted from measurements of the field emission current. These results are compared with the tests performed on 30 GHz test accelerating structures for the future Compact Linear Collider.

  12. Direct relationship between breakdown strength and tracking index of composites

    DEFF Research Database (Denmark)

    Madsen, Søren Find; Henriksen, Mogens; Holbøll, Joachim

    2006-01-01

    The following paper shows a clear correlation between the measured tracking index and the breakdown field strength for noncoated glass fibre reinforced polymers (GFRP) with either a polyester or an epoxy based resin. 17 types of specimens have been tested according to IEC Publication 60587. The...... breakdown field strength of specimens cut from similar samples is determined by a new method capable of estimating the stressed volume. The results from the two tests are finally compared and incorporated in a single analytical formula. All test specimens are supplied by Danish manufacturers of wind turbine...

  13. Breakdown voltage in thin III-V avalanche photodiodes

    Science.gov (United States)

    Saleh, Mohammad A.; Hayat, Majeed M.; Kwon, Oh-Hyun; Holmes, Archie L.; Campbell, Joe C.; Saleh, Bahaa E. A.; Teich, Malvin C.

    2001-12-01

    The dead-space multiplication theory of Hayat and Saleh [J. Lightwave Technol. 10, 1415 (1992)], in conjunction with the multiplication-width-independent ionization-coefficient model developed by Saleh et al. [IEEE Trans. Electron Devices 47, 625 (2000)], are shown to accurately predict breakdown voltages for thin avalanche photodiodes of GaAs, InP, In0.52Al0.48As, and Al0.2Ga0.8As, over a broad range of device widths. The breakdown voltage is determined from the analytical expression for the impulse-response-function decay rate.

  14. High breakdown-strength composites from liquid silicone rubbers

    DEFF Research Database (Denmark)

    Vudayagiri, Sindhu; Zakaria, Shamsul Bin; Yu, Liyun;

    2014-01-01

    available fillers (an anatase TiO2, a core–shell TiO2-SiO2 and a CaCu3Ti4O12 filler) are evaluated with respect to dielectric permittivity, elasticity (Young’s modulus) and electrical breakdown strength. Film formation properties are also evaluated. The best-performing formulations are those with anatase Ti......O2 nanoparticles, where the highest relative dielectric permittivity of 5.6 is obtained, and with STX801, a core–shell morphology TiO2-SiO2 filler from Evonik, where the highest breakdown strength of 173 V μm−1 is obtained....

  15. Infrared laser-induced breakdown spectroscopy emissions from energetic materials

    Science.gov (United States)

    Yang, Clayton S.; Brown, E.; Hommerich, Uwe; Trivedi, Sudhir B.; Samuels, Alan C.; Snyder, A. Peter

    2011-05-01

    Laser-induced breakdown spectroscopy (LIBS) has shown great promise for applications in chemical, biological, and explosives (CBE) sensing and has significant potential for real time standoff detection and analysis. We have studied LIBS emissions in the mid-infrared (MIR) spectral region for potential applications in CBE sensing. Detailed MIR-LIBS studies were performed for several energetic materials for the first time. In this study, the IR signature spectral region between 4 - 12 um was mined for the appearance of MIR-LIBS emissions that are directly indicative of oxygenated breakdown products as well as partially dissociated and recombination molecular species.

  16. Molecular hydrogen in strong laser fields: breakdown(s) of the fixed-nuclei approximation

    International Nuclear Information System (INIS)

    We investigate the effect of nuclear vibration on the ionization behaviour of molecular hydrogen by a direct solution of the time-dependent Schroedinger equation. For this purpose, our six-dimensional configuration-interaction method to solve the electronic Schroedinger equation of molecular hydrogen in strong laser fields is extended to include molecular vibration. The results obtained within the correlated treatment of electronic and vibrational motion are compared to those stemming from the fixed-nuclei approximation (FNA; i.e. the solution of the electronic Schroedinger equation only for the equilibrium geometry). We show that the FNA breaks down for certain laser parameters in the multiphoton and quasistatic regimes. For example, the total ionization yield can differ from the ''full'' treatment by several orders of magnitude. The reasons for these complete breakdowns of the FNA are explained and it is shown that other very simple (and ''useful'') approximations still agree surprisingly well with the ''full'' treatment.

  17. CANCER-PAthological breakdown of coherent energy states

    Czech Academy of Sciences Publication Activity Database

    Pokorný, Jiří; Pokorný, Jan; Kobilková, J.; Jandová, Anna; Vrba, J.; Vrba, J. jr.

    2014-01-01

    Roč. 9, č. 1 (2014), s. 115-133. ISSN 1793-0480 Institutional support: RVO:67985882 ; RVO:68378271 Keywords : breakdown of coherent states * Cancer electrodynamics * Warburg effect Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering; BO - Biophysics (FZU-D)

  18. Controlled electron emission and vacuum breakdown with nanosecond pulses

    Science.gov (United States)

    Seznec, B.; Dessante, Ph; Caillault, L.; Babigeon, J.-L.; Teste, Ph; Minea, T.

    2016-06-01

    Vacuum electron sources exploiting field emission are generally operated in direct current (DC) mode. The development of nanosecond and sub-nanosecond pulsed power supplies facilitates the emission of compact bunches of electrons of high density. The breakdown level is taken as the highest value of the voltage avoiding the thermo-emission instability. The effect of such ultra-fast pulses on the breakdown voltage and the emitted electron current is discussed as a result of the thermo-emission modelling applied to a significant protrusion. It is found that pulsing very rapidly the vacuum breakdown occurs at higher voltage values than for the DC case, because it rises faster than the heat diffusion. In addition, the electron emission current increases significantly regardless of the theoretical approach is used. A comparative study of this theoretical work is discussed for several different forms of the protrusion (elliptic and hyperbolic) and different metals (hence varying the melting point), particularly refractory (tungsten) versus conductor (titanium). Pulsed mode operation can provide an increase on breakdown voltage (up to 18%) and a significant increase (up to 330%) of the electron extracted current due to its high non-linear dependency with the voltage, for the case for the case with a hyperbolic protrusion.

  19. Time-to-breakdown characteristics of magnetic tunnel junctions

    International Nuclear Information System (INIS)

    To investigate the reliability of the MTJs on the roughness of insulating tunnel barrier, we prepared two MTJs with the different uniformity of barrier thickness. Namely, the one has uniform insulating barrier thickness; the other has non-uniform insulating barrier thickness as compared to different thing. As to depositing amorphous layer CoZrNb under the pinning layer IrMn, we achieved MTJ with uniform barrier thickness. First of all, we performed the breakdown-voltage measurement of two junctions and obtained the result having a similar breakdown-voltage about 1.4 V at two all junctions. And then, the time dependence dielectric breakdown (TDDB) measurements of two junctions are carried out under constant voltage stresses. The Weibull fit of our data shows clearly that time to breakdown (tBD) scales with the thickness uniformity of tunnel barrier. And also, Assuming a linear dependence of log(tBD) on stress voltages, we meet with result about the different lifetime of the two MTJs with uniform barrier thickness or non-uniform barrier thickness. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Time-to-breakdown characteristics of magnetic tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Jae Youn; Rhee, Jang Roh [Department of Physics, Sookmyung Women' s University, Seoul 140-742 (Korea); Kim, Taewan; Park, Wanjun [Materials and Devices Laboratory, Samsung Advanced Institute of Technology, Gyeonggi-Do 449-711 (Korea); Jang, YoungMan; Cho, B.K. [Superconducting and Magnetic Materials Laboratory, GwangJu Institute of Science and Technology, Gwangju 500-712 (Korea)

    2004-12-01

    To investigate the reliability of the MTJs on the roughness of insulating tunnel barrier, we prepared two MTJs with the different uniformity of barrier thickness. Namely, the one has uniform insulating barrier thickness; the other has non-uniform insulating barrier thickness as compared to different thing. As to depositing amorphous layer CoZrNb under the pinning layer IrMn, we achieved MTJ with uniform barrier thickness. First of all, we performed the breakdown-voltage measurement of two junctions and obtained the result having a similar breakdown-voltage about 1.4 V at two all junctions. And then, the time dependence dielectric breakdown (TDDB) measurements of two junctions are carried out under constant voltage stresses. The Weibull fit of our data shows clearly that time to breakdown (t{sub BD}) scales with the thickness uniformity of tunnel barrier. And also, Assuming a linear dependence of log(t{sub BD}) on stress voltages, we meet with result about the different lifetime of the two MTJs with uniform barrier thickness or non-uniform barrier thickness. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Pattern Analysis on DC Breakdown Phenomenon of Polyethylene Films

    Institute of Scientific and Technical Information of China (English)

    DU Boxue; LIU Yong; LIU Hongjing

    2006-01-01

    Pattern analysis method was used to study DC breakdown characteristics of low-density polyethylene(LDPE)film and high-density polyethylene(HDPE)film, with particular attention paid to the breakdown phenomenon identification. The breakdown pattern(BP)was recorded by a monocular-video-zoom microscope. The records showed that the effective area of BP was almost identical to the types of electrodes. The effective area was calculated by a mathematical integral method. The diameter was obtained by a mathematical statistic method. The study revealed that the DC breakdown voltage of LDPE was lower than that of HDPE. The diameter and effective area of LDPE were smaller than those of HDPE, but it is opposite for the condition of the needle-plane electrode with plane electrode grounded. As for the needle-plane electrode, the diameter and effective area with the films near the needle electrode were smaller than those near the plane electrode, and those in the middle of air gap were between them. As for the sphere-plane electrode, the diameter and effective area with the films near the plane electrode were smaller than those near the sphere electrode, and those in the middle of air gap were between them.

  2. RF Breakdown in Normal Conducting Single-Cell Structures

    International Nuclear Information System (INIS)

    Operating accelerating gradient in normal conducting accelerating structures is often limited by rf breakdown. The limit depends on multiple parameters, including input rf power, rf circuit, cavity shape and material. Experimental and theoretical study of the effects of these parameters on the breakdown limit in full scale structures is difficult and costly. We use 11.4 GHz single-cell traveling wave and standing wave accelerating structures for experiments and modeling of rf breakdown behavior. These test structures are designed so that the electromagnetic fields in one cell mimic the fields in prototype multicell structures for the X-band linear collider. Fields elsewhere in the test structures are significantly lower than that of the single cell. The setup uses matched mode converters that launch the circular TM01 mode into short test structures. The test structures are connected to the mode launchers with vacuum rf flanges. This setup allows economic testing of different cell geometries, cell materials and preparation techniques with short turn-around time. Simple 2D geometry of the test structures simplifies modeling of the breakdown currents and their thermal effects

  3. Effects of streamwise vortex breakdown on supersonic combustion.

    Science.gov (United States)

    Hiejima, Toshihiko

    2016-04-01

    This paper presents a numerical simulation study of the combustion structure of streamwise vortex breakdown at Mach number 2.48. Hydrogen fuel is injected into a combustor at sonic speed from the rear of a hypermixer strut that can generate streamwise vortices. The results show that the burning behavior is enhanced at the points of the shock waves that are incident on the vortex and therefore the vortex breakdown in the subsonic region occurs due to combustion. The breakdown domain in the mainstream is found to form a flame-holding region suited to combustion and to lead to a stable combustion field with detached flames. In this way, streamwise vortex breakdown has an essential role in combustion enhancement and the formation of flames that hold under supersonic inflow conditions. Finally, the combustion property defined here is shown to coincide with the produced-water mass flow. This property shows that the amount of combustion is saturated at equivalence ratios over 0.4, although there is a slight increase beyond 1. PMID:27176398

  4. RF breakdown of 805 MHz cavities in strong magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Bowring, D. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Stratakis, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Kochemirovskiy, A. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Leonova, M. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Moretti, A. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Palmer, M. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Peterson, D. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Yonehara, K. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Freemire, B. [Illinois Inst. of Technology, Chicago, IL (United States); Lane, P. [Illinois Inst. of Technology, Chicago, IL (United States); Torun, Y. [Illinois Inst. of Technology, Chicago, IL (United States); Haase, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-05-03

    Ionization cooling of intense muon beams requires the operation of high-gradient, normal-conducting RF structures in the presence of strong magnetic fields. We have measured the breakdown rate in several RF cavities operating at several frequencies. Cavities operating within solenoidal magnetic fields B > 0.25 T show an increased RF breakdown rate at lower gradients compared with similar operation when B = 0 T. Ultimately, this breakdown behavior limits the maximum safe operating gradient of the cavity. Beyond ionization cooling, this issue affects the design of photoinjectors and klystrons, among other applications. We have built an 805 MHz pillbox-type RF cavity to serve as an experimental testbed for this phenomenon. This cavity is designed to study the problem of RF breakdown in strong magnetic fields using various cavity materials and surface treatments, and with precise control over sources of systematic error. We present results from tests in which the cavity was run with all copper surfaces in a variety of magnetic fields.

  5. A numerical study of three-dimensional vortex breakdown

    Science.gov (United States)

    Spall, Robert E.; Ash, Robert L.

    1987-01-01

    A numerical simulation of bubble-type vortex breakdown using a unique discrete form of the full 3-D, unsteady incompressible Navier-Stokes equations was performed. The Navier-Stokes equations were written in a vorticity-velocity form and the physical problem was not restricted to axisymmetric flow. The problem was parametized on a Rossby- Reynolds-number basis. Utilization of this parameter duo was shown to dictate the form of the free-field boundary condition specification and allowed control of axial breakdown location within the computational domain. The structure of the breakdown bubble was studied through time evolution plots of planar projected velocity vectors as well as through plots of particle traces and vortex lines. These results compared favorably with previous experimental studies. In addition, profiles of all three velocity components are presented at various axial stations and a Fourier analysis was performed to identify the dominant circumferential modes. The dynamics of the breakdown process were studied through plots of axial variation of rate of change of integrated total energy and rate of change of integrated enstrophy, as well as through contour plots of velocity, vorticity and pressure.

  6. Autism Spectrum Disorder in Children Adopted after Early Care Breakdown

    Science.gov (United States)

    Green, Jonathan; Leadbitter, Kathy; Kay, Catherine; Sharma, Kishan

    2016-01-01

    Syndromic autism has been described in children adopted after orphanage rearing. We investigated whether the same existed in children adopted after family breakdown. Families of 54/60 adopted children aged 6-11 years (mean 102 months; SD 20; 45% male) returned screening questionnaires for autism spectrum disorder (ASD); 21/54 (39%) screened…

  7. The breakdown phase in a coaxial plasma gun

    International Nuclear Information System (INIS)

    The electrical breakdown in a coaxial plasma gun was investigated by means of optical and electrical measurements. The optimum start and operation conditions of the gun turned out to be strongly dependent on material and length of the cylindrical insulator. (orig.)

  8. Overview of applications of Laser-Induced Breakdown Spectroscopy (LIBS)

    International Nuclear Information System (INIS)

    Laser-induced breakdown spectroscopy (LIBS) is a method of performing elemental analyses of solids, liquids, and gases using the microplasma produced by a focused laser pulse. Because the microplasma is formed by optical radiation, LIBS has some important advantages compared to conventional laboratory based analytical methods. Three applications are discussed which use the LIBS method. 6 refs., 8 figs., 2 tabs

  9. The electrical breakdown of thin dielectric elastomers: thermal effects

    Science.gov (United States)

    Zakaria, Shamsul; Morshuis, Peter H. F.; Benslimane, Mohamed Y.; Gernaey, Krist V.; Skov, Anne L.

    2014-03-01

    Dielectric elastomers are being developed for use in actuators, sensors and generators to be used in various applications, such as artificial eye lids, pressure sensors and human motion energy generators. In order to obtain maximum efficiency, the devices are operated at high electrical fields. This increases the likelihood for electrical breakdown significantly. Hence, for many applications the performance of the dielectric elastomers is limited by this risk of failure, which is triggered by several factors. Amongst others thermal effects may strongly influence the electrical breakdown strength. In this study, we model the electrothermal breakdown in thin PDMS based dielectric elastomers in order to evaluate the thermal mechanisms behind the electrical failures. The objective is to predict the operation range of PDMS based dielectric elastomers with respect to the temperature at given electric field. We performed numerical analysis with a quasi-steady state approximation to predict thermal runaway of dielectric elastomer films. We also studied experimentally the effect of temperature on dielectric properties of different PDMS dielectric elastomers. Different films with different percentages of silica and permittivity enhancing filler were selected for the measurements. From the modeling based on the fitting of experimental data, it is found that the electrothermal breakdown of the materials is strongly influenced by the increase in both dielectric permittivity and conductivity.

  10. Electrical Breakdown and Mechanical Ageing in Dielectric Elastomers

    DEFF Research Database (Denmark)

    Zakaria, Shamsul Bin

    Dielectric elastomers (DE) are used in various applications, such as artificial eye lids, pressure sensors and human motion energy generators. For many applications, one of the major factors that limits the DE performance is premature electrical breakdown. There are many approaches that have been...

  11. Laser-Induced Breakdown Spectroscopy and Chlorophyll a Flourescence Transients

    DEFF Research Database (Denmark)

    Frydenvang, Jens

    trustworthy results of a sufficient quality; something that remains a problem for many in-situ methods. In my PhD, I present my work with two such in-situ methods, Laser-Induced Breakdown Spectroscopy (LIBS) and OJIP transients, the rising part of chlorophyll a fluorescence transients from dark-adapted leaves....

  12. Local late Amazonian boulder breakdown and denudation rate on Mars

    NARCIS (Netherlands)

    de Haas, T.; Hauber, E.; Kleinhans, M.G.

    2013-01-01

    Inactive fan surfaces become smoother and develop desert pavement over time by weathering and erosion. We use this mechanism to estimate late Amazonian boulder breakdown and surface denudation rates on a young (∼1.25 Ma) (Schon et al., 2009) fan on Mars. This is done by comparing boulder size and su

  13. Marital Breakdown, Shame, and Suicidality in Men: A Direct Link?

    Science.gov (United States)

    Kolves, Kairi; Ide, Naoko; De Leo, Diego

    2011-01-01

    The influence of feelings of shame originating from marital breakdown on suicidality is examined. The role of mental health problems as probable mediating factors is also considered. Internalized shame, state (related to separation) shame, and mental health problems were significantly correlated with the score for suicidality during separation in…

  14. A study of vortex breakdown in supercritical fluids

    Science.gov (United States)

    Crook, Loren C.

    The objective of this thesis is to evaluate the hydrodynamic stability theory of vortex breakdown by examining its presence in a swirling supercritical fluid jet. Supercritical fluids were chosen because they are technologically important, and because their strong density gradients near the critical point provide a self-excitable flow regime where hydrodynamic instabilities should be more easily identified. Computations were developed to provide flow conditions for experimental observation of vortex breakdown and to estimate hydrodynamic flow instabilities prior to testing. The RANS computations of an axial-plus-tangential air swirler were developed and verified as grid-independent and in agreement with experimental results reported in the literature. The computations also produced a correlation of momentum swirl number as a function of mass ratio (tangential/total) for estimating swirl number during experiments. Finally, the computations were extended to simulate supercritical CO2 in an axial-plus-tangential swirler that was compatible with the supercritical injection facility. Three mass flow ratio cases were investigated extensively: no-swirl (0%), low-swirl prior to breakdown (25%), and moderate swirl with breakdown (45%). (The three corresponding momentum swirl numbers for these mass flow ratios were 0.0, 0.30 and 0.80.) These three cases also served as the basis for the experimental portion of the work. Swirling supercritical fluid jets were observed in the injection facility using schlieren imaging for three separate swirl numbers. The Sobel method was used to locate the jet edges. The jets were characterized by their radii, including mean and standard deviation, and spreading angles as functions of swirl number and density ratio (2.3, 2.6, and 5.0). The swirl number was identified as the dominant parameter in determining the spreading angle and jet radius. Vortex breakdown was identified as the jet structure changed from straight edges to curved, signifying

  15. Comprehensive Definitions of Breakdown-Points for Independent and Dependent Observations

    OpenAIRE

    M. G. Genton; Lucas, A.

    2000-01-01

    We provide a new definition of breakdown in finite samples with an extension to asymptotic breakdown. Previous definitions center around defining a critical region for either the parameter or the objective function. If for a particular outlier constellation the critical region is entered, breakdown is said to occur. In contract to the traditional approach, we leave the definition of the critical region implicit. Our definition encompasses all previousdefinitions of breakdown in both linear an...

  16. Calculation of Spark Breakdown or Corona Starting Voltages in Nonuniform Fields

    DEFF Research Database (Denmark)

    Pedersen, A.

    1967-01-01

    The processes leading to a spark breakdown or corona discharge are discussed very briefly. A quantitative breakdown criterion for use in high-voltage design is derived by which spark breakdown or corona starting voltages in nonuniform fields can be calculated. The criterion is applied to the sphere...

  17. Breakdown characteristics in DC spark experiments of copper focusing on purity and hardness

    International Nuclear Information System (INIS)

    To investigate the breakdown characteristic of differences in purity and hardness, three samples of copper, oxygen-free copper (OFC), 7-nine large-grain copper and 6-nine hot-isotropic-pressed copper, were tested with the DC spark system at CERN. Measurements of beta, breakdown fields and breakdown probability are presented in this paper. (author)

  18. Laser-induced breakdown emission in hydrocarbon fuel mixtures

    Science.gov (United States)

    Kobayashi, Kazunobu; Bak, Moon Soo; Tanaka, Hiroki; Carter, Campbell; Do, Hyungrok

    2016-04-01

    Time-resolved emission measurements of laser-induced breakdown plasmas have been carried out to investigate the effect that gas species might have on the kinetics, particularly in excited states, and the resulting plasma properties. For this purpose, fuel-oxygen (O2)-carbon dioxide (CO2) mixtures with either helium (He) or nitrogen (N2) balance are prepared while maintaining their atomic compositions. The fuels tested in this study are methane (CH4), ethylene (C2H4), propane (C3H8), and butane (C4H10). The breakdown is produced in the mixtures (CH4/CO2/O2/He, C2H4/O2/He, C3H8/CO2/O2/He and C4H10/CO2/O2/He or CH4/CO2/O2/N2, C2H4/O2/N2, C3H8/CO2/O2/N2 and C4H10/CO2/O2/N2) at room conditions using the second harmonic of a Q-switched Nd:YAG laser (with pulse duration of 10 ns). The temporal evolution of plasma temperature is deduced from the ratio of two oxygen lines (777 nm and 823 nm) through Boltzmann analysis, while the evolution of electron number density is estimated based on Stark broadening of the Balmer-alpha (H α ) line at 656 nm and the measured plasma temperature. From the results, the temporal evolution of emission spectra and decay rates of atomic line-intensities are found to be almost identical between the breakdown plasma in the different mixtures given balancing gases. Furthermore, the temporal evolution of plasma temperature and electron number density are also found to be independent of the species compositions. Therefore, this behavior—of the breakdown emissions and plasma properties in the different mixtures with identical atomic composition—may be because the breakdown gases reach similar thermodynamic and physiochemical states immediately after the breakdown.

  19. Research of Dielectric Breakdown Micro fluidic Sampling Chip

    International Nuclear Information System (INIS)

    Micro fluidic chip is mainly driven electrically by external electrode and array electrode, but there are certain disadvantages in both of ways, which affect the promotion and application of micro fluidic technology. This paper discusses a scheme that uses the conductive solution in a microchannel made by PDMS, replacing electrodes and the way of dielectric breakdown to achieve microfluidic chip driver. It could reduce the driving voltage and simplify the chip production process. To prove the feasibility of this method, we produced a micro fluidic chip used in PDMS material with the lithography technology and experimented it. The results showed that using the dielectric breakdown to achieve microfluidic chip driver is feasible, and it has certain application prospect.

  20. Critical effects of downstream boundary conditions on vortex breakdown

    Science.gov (United States)

    Kandil, Osama; Kandil, Hamdy A.; Liu, C. H.

    1992-01-01

    The unsteady, compressible, full Navier-Stokes (NS) equations are used to study the critical effects of the downstream boundary conditions on the supersonic vortex breakdown. The present study is applied to two supersonic vortex breakdown cases. In the first case, quasi-axisymmetric supersonic swirling flow is considered in a configured circular duct, and in the second case, quasi-axisymmetric supersonic swirling jet, that is issued from a nozzle into a supersonic jet of lower Mach number, is considered. For the configured duct flow, four different types of downstream boundary conditions are used, and for the swirling jet flow from the nozzle, two types of downstream boundary conditions are used. The solutions are time accurate which are obtained using an implicit, upwind, flux-difference splitting, finite-volume scheme.

  1. Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown

    International Nuclear Information System (INIS)

    Boron Nitride (BN) is a two dimensional insulator with excellent chemical, thermal, mechanical, and optical properties, which make it especially attractive for logic device applications. Nevertheless, its insulating properties and reliability as a dielectric material have never been analyzed in-depth. Here, we present the first thorough characterization of BN as dielectric film using nanoscale and device level experiments complementing with theoretical study. Our results reveal that BN is extremely stable against voltage stress, and it does not show the reliability problems related to conventional dielectrics like HfO2, such as charge trapping and detrapping, stress induced leakage current, and untimely dielectric breakdown. Moreover, we observe a unique layer-by-layer dielectric breakdown, both at the nanoscale and device level. These findings may be of interest for many materials scientists and could open a new pathway towards two dimensional logic device applications

  2. Breakdown of molecular oxygen by brief pulses of laser radiation

    International Nuclear Information System (INIS)

    We report a numerical analysis for the combined action of multi-photon (MPHI) and Cascade ionization (CI) processes in producing ionization and breakdown of molecular oxygen. The calculations were carried out at two different laser pulses of wavelengths 0.6943μm and 0.53μm with pulse durations 18ps and 25ps respectively, over a pressure range of 102-5x104 Torr. A reasonably good agreement has been obtained between the computed threshold intensities and the measured ones. Computations for nitrogen irradiated with 0.53μm are also given. This analysis shows that the model is capable to interpret gas breakdown experiments with short flashes of laser radiation. (author). 6 refs, 5 figs

  3. Partial discharges and breakdown in C3F8

    International Nuclear Information System (INIS)

    Traditional search processes of gases or gas mixtures for replacing SF6 involve time consuming measurements of partial discharges and breakdown behaviour for several voltage waveforms and different field configurations. Recently a model for prediction of this behaviour for SF6 was described in literature. The model only requires basic properties of the gas such as the critical field strength and the effective ionization coefficient, which can be obtained by swarm parameter measurements, and thermodynamic properties, which can be calculated. In this paper, we show for the well-known and electronegative gas octafluoropropane (C3F8) that it is possible to transfer the model developed for SF6 to this gas to describe the breakdown behaviour of C3F8. Thus the model can be beneficial in the screening process of new insulation gases. (paper)

  4. Local late Amazonian boulder breakdown and denudation rate on Mars

    Science.gov (United States)

    Haas, Tjalling; Hauber, Ernst; Kleinhans, Maarten G.

    2013-07-01

    Inactive fan surfaces become smoother and develop desert pavement over time by weathering and erosion. We use this mechanism to estimate late Amazonian boulder breakdown and surface denudation rates on a young (˜1.25 Ma) (Schon et al., 2009) fan on Mars. This is done by comparing boulder size and surface relief between lobes of different ages. The boulder breakdown rate is 3.5 m/Myr, surface smoothing (denudation) rate is approximated as 0.89 m/Myr. These rates exceed previous estimates for the Amazonian by orders of magnitude. We attribute this to locality, high initial smoothing rates after morphological activity and obliquity and eccentricity-driven variation in the availability of (metastable) liquid water, which acts as a catalyst for weathering during these periods. The results have major implications for process interpretation of Martian landforms, as they imply that typical small-scale morphology may be subdued within <1 Myr.

  5. Interpopulation hybrid breakdown maps to the mitochondrial genome.

    Science.gov (United States)

    Ellison, Christopher K; Burton, Ronald S

    2008-03-01

    Hybrid breakdown, or outbreeding depression, is the loss of fitness observed in crosses between genetically divergent populations. The role of maternally inherited mitochondrial genomes in hybrid breakdown has not been widely examined. Using laboratory crosses of the marine copepod Tigriopus californicus, we report that the low fitness of F(3) hybrids is completely restored in the offspring of maternal backcrosses, where parental mitochondrial and nuclear genomic combinations are reassembled. Paternal backcrosses, which result in mismatched mitochondrial and nuclear genomes, fail to restore hybrid fitness. These results suggest that fitness loss in T. californicus hybrids is completely attributable to nuclear-mitochondrial genomic interactions. Analyses of ATP synthetic capacity in isolated mitochondria from hybrid and backcross animals found that reduced ATP synthesis in hybrids was also largely restored in backcrosses, again with maternal backcrosses outperforming paternal backcrosses. The strong fitness consequences of nuclear-mitochondrial interactions have important, and often overlooked, implications for evolutionary and conservation biology. PMID:18081717

  6. Does Expectation of Correlation Breakdown in Financial Market Fulfill Itself?

    Directory of Open Access Journals (Sweden)

    Paolo Falbo

    2015-01-01

    Full Text Available This paper develops a model appeared in the literature whose focus was the way rational risk averse investors anticipate the correlation breakdowns of asset returns in periods of excess demand. That model analysed the dynamics of the “expected” returns of the risky asset, and their consistency with empirical evidence. However, the same model did not provide any evidence on actual correlation generated by the dynamics of returns. A model to link asset returns to excess demand is required to analyse the implied correlation between the securities traded. In this work we estimate such a model. Results confirm that the expected and ex-post correlation tend to move closely. In other words a self-fulfilling prophecy about correlation breakdown can take place, even when rational agents dominate the financial market.

  7. Risky business: Preventing skin breakdown in children with spina bifida.

    Science.gov (United States)

    Ekmark, Elaine McGarr

    2009-01-01

    The purpose of this article is to provide an overview of skin issues in children with spina bifida. Included in the discussion below is a review of the etiology of pressure ulcers and the updated 2007 pressure ulcer definition and pressure ulcer staging system as defined by the National Pressure Ulcer Advisory Panel (NPUAP). Pediatric risk factors for skin breakdown are presented including risk factors unique to children with spina bifida. Pediatric pressure ulcer risk assessment scales are described. The 5 Million Lives Kids' Campaign which has a focus on preventing hospital-acquired pressure ulcers in children is also reviewed along with evidence based prevention strategies. The key to preventing skin breakdown and pressure ulcers in children with spina bifida is early identification of the child's individual risk factors so that a prevention protocol can be implemented in all settings: hospital, home and the community. Options for wound management, dressing selection and pain management are included. PMID:21791793

  8. Possibility of increasing the optical breakdown threshold in KDP crystals

    International Nuclear Information System (INIS)

    The effect of various technological factors like the direction of crystal growth [(100) or (101)], acidity of the mother solution, growth rate, degree of filtration of the mother solution, purity of the starting raw material, specially introduced impurity (Pb), as well as after-growth thermal annealing, on the optical breakdown threshold of KDP crystals grown by the technique of rapid growth of profiled crystals is studied. It is shown that by using initial high-purity salts and fine filtration of solutions followed by after-growth annealing, it is possible to increase the optical breakdown threshold of profiled rapidly grown KDP crystals to values corresponding to the requirements of modern laser designs. (laser devices and elements)

  9. Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Yanfeng; Pan, Chengbin; Hui, Fei; Shi, Yuanyuan; Lanza, Mario, E-mail: mlanza@suda.edu.cn [Institute of Functional Nano and Soft Materials, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, 199 Ren-Ai Road, Suzhou 215123 (China); Zhang, Meiyun; Long, Shibing [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Lian, Xiaojuan; Miao, Feng [National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Larcher, Luca [DISMI, Università di Modena e Reggio Emilia, 42122 Reggio Emilia (Italy); Wu, Ernest [IBM Research Division, Essex Junction, Vermont 05452 (United States)

    2016-01-04

    Boron Nitride (BN) is a two dimensional insulator with excellent chemical, thermal, mechanical, and optical properties, which make it especially attractive for logic device applications. Nevertheless, its insulating properties and reliability as a dielectric material have never been analyzed in-depth. Here, we present the first thorough characterization of BN as dielectric film using nanoscale and device level experiments complementing with theoretical study. Our results reveal that BN is extremely stable against voltage stress, and it does not show the reliability problems related to conventional dielectrics like HfO{sub 2}, such as charge trapping and detrapping, stress induced leakage current, and untimely dielectric breakdown. Moreover, we observe a unique layer-by-layer dielectric breakdown, both at the nanoscale and device level. These findings may be of interest for many materials scientists and could open a new pathway towards two dimensional logic device applications.

  10. Analysis of organic vapors with laser induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    In this paper, laser induced breakdown spectroscopy (LIBS) is utilized in the study of acetone, ethanol, methanol, cyclohexane, and nonane vapors. Carbon, hydrogen, oxygen, and nitrogen atomic emission spectra have been recorded following laser-induced breakdown of the organic vapors that are mixed with air inside a quartz chamber at atmospheric pressure. The plasma is generated with focused, Q-switched Nd:YAG radiation at the wavelength of 1064 nm. The effects of ignition and vapor pressure are discussed in view of the appearance of the emission spectra. The recorded spectra are proportional to the vapor pressure in air. The hydrogen and oxygen contributions diminish gradually with consecutive laser-plasma events without gas flow. The results show that LIBS can be used to characterize organic vapor

  11. High voltage breakdown in an inductively coupled ion source

    International Nuclear Information System (INIS)

    An inductively coupled plasma source, designed for ion beam applications, is allowed to float up to several kilovolt positive. If one side of the radio frequency (rf) antenna is grounded and the dielectric source tube and the surrounding air are allowed to reach a threshold temperature corona breakdown at the rf antenna occurs. The experiments presented here show that a dc corona can be ignited with the presence of a dielectric barrier, which normally precludes dc breakdown. The formation of a negative barrier corona initiates a transition to a continuous arc from the rf antenna to the source tube. It is suggested that the onset of the first filaments heat the dielectric locally, such that the dielectric strength drops. DC current channels are then formed in the source tube, allowing a resistive corona with continuous arcs to exist

  12. Microwave and optical breakdown of gases in pulse superpower fields

    International Nuclear Information System (INIS)

    The analytical review of theoretical works on the gas breakdown in the pulse superpower fields of the microwave and optical radiation is carried out under the conditions, when the electron oscillation energy in the radiation wave field by far exceeds the energy of the gas atoms ionization. Such fields in the microwave area are much smaller as the atomic field and therefore the mechanism of the gas atoms ionization is determined by development of the ionization avalanche through the electron collision. The fields in the optical area of frequencies are comparable with the atomic field and the mechanism of the gas atoms ionization is conditioned by the bound electrons tunneling. In spite of this the electrons distribution functions in both cases are similar and are characterized by pronounced anisotropy, which essentially effects the plasma breakdown stability

  13. Analysis of organic vapors with laser induced breakdown spectroscopy

    Science.gov (United States)

    Nozari, Hadi; Rezaei, Fatemeh; Tavassoli, Seyed Hassan

    2015-09-01

    In this paper, laser induced breakdown spectroscopy (LIBS) is utilized in the study of acetone, ethanol, methanol, cyclohexane, and nonane vapors. Carbon, hydrogen, oxygen, and nitrogen atomic emission spectra have been recorded following laser-induced breakdown of the organic vapors that are mixed with air inside a quartz chamber at atmospheric pressure. The plasma is generated with focused, Q-switched Nd:YAG radiation at the wavelength of 1064 nm. The effects of ignition and vapor pressure are discussed in view of the appearance of the emission spectra. The recorded spectra are proportional to the vapor pressure in air. The hydrogen and oxygen contributions diminish gradually with consecutive laser-plasma events without gas flow. The results show that LIBS can be used to characterize organic vapor.

  14. Analysis of organic vapors with laser induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nozari, Hadi; Tavassoli, Seyed Hassan [Laser and Plasma Research Institute, Shahid Beheshti University, G. C, 1983963113 Evin, Tehran (Iran, Islamic Republic of); Rezaei, Fatemeh, E-mail: fatemehrezaei@kntu.ac.ir [Department of Physics, K. N. Toosi University of Technology, 15875-4416 Shariati, Tehran (Iran, Islamic Republic of)

    2015-09-15

    In this paper, laser induced breakdown spectroscopy (LIBS) is utilized in the study of acetone, ethanol, methanol, cyclohexane, and nonane vapors. Carbon, hydrogen, oxygen, and nitrogen atomic emission spectra have been recorded following laser-induced breakdown of the organic vapors that are mixed with air inside a quartz chamber at atmospheric pressure. The plasma is generated with focused, Q-switched Nd:YAG radiation at the wavelength of 1064 nm. The effects of ignition and vapor pressure are discussed in view of the appearance of the emission spectra. The recorded spectra are proportional to the vapor pressure in air. The hydrogen and oxygen contributions diminish gradually with consecutive laser-plasma events without gas flow. The results show that LIBS can be used to characterize organic vapor.

  15. Time-resolved laser-induced breakdown spectroscopy of aluminum

    Institute of Scientific and Technical Information of China (English)

    LIU Xian-yun; ZHANG Wei-jun; WANG Zhen-ya; HAO Li-qing; HUANG Ming-qiang; ZHAO Wen-wu; LONG Bo; Zhao Wei

    2008-01-01

    We develop a system to measure the elemental composition of unprepared samples using laser-induced breakdown spectroscopy (LIBS) in our laboratory, which can be used for the determination of elements in solids, liquids and aerosols. A description of the instrumentation, including laser, sample chamber and detection, is followed by a brief discussion. The time-resolved LIBS of aluminum at atmospheric pressure is presented. At the end, the possibilities and later uses of this technique are briefly discussed.

  16. Financial market breakdown due to strategy constraints and information asymmetry

    OpenAIRE

    Hu, Jie

    1995-01-01

    This paper demonstrates the relevance of strategy constraints on market makers to the possibility of financial market breakdown when there is information asymmetry between market makers and investors; both the case of competitive market makers and the case of a monopolistic market marker are included. Specifically, the paper discusses three types of strategy constraints on the market makers and their implications for the equilibria. The results call attention to the need for more precise spec...

  17. Integrating nanopore sensors within microfluidic channel arrays using controlled breakdown.

    Science.gov (United States)

    Tahvildari, Radin; Beamish, Eric; Tabard-Cossa, Vincent; Godin, Michel

    2015-03-21

    Nanopore arrays are fabricated by controlled dielectric breakdown (CBD) in solid-state membranes integrated within polydimethylsiloxane (PDMS) microfluidic devices. This technique enables the scalable production of independently addressable nanopores. By confining the electric field within the microfluidic architecture, nanopore fabrication is precisely localized and electrical noise is significantly reduced. Both DNA and protein molecules are detected to validate the performance of this sensing platform. PMID:25631885

  18. Advanced Breakdown Modeling for Solid-State Circuit Design

    OpenAIRE

    Milovanović, V.

    2010-01-01

    Modeling of the effects occurring outside the usual region of application of semiconductor devices is becoming more important with increasing demands set upon electronic systems for simultaneous speed and output power. Analog integrated circuit designers are forced to enter regimes of transistor operation that are close to or within the device breakdown. They use compact models that describe device behavior in an efficient way to predict a designed circuit performance. Using modern heterojunc...

  19. DC breakdown field measurements of heat treated molybdenum

    CERN Document Server

    Calatroni, Sergio; Ramsvik, T; Taborelli, M; CERN. Geneva. TS Department

    2008-01-01

    The effect of heat treatments of molybdenum on the resistance to breakdown and conditioning speed has been investigated in the DC spark setup. The conditioning speed is strongly improved by treatment at 875C in UHV ex situ compared to chemically cleaned surfaces. This temperature is sufficiently low to prevent a re-crystallization of the material which could influence mechanical properties, as hardness. The saturation field remains unchanged. The beneficial effect is preserved for 8 h of air exposure after treatment.

  20. Ionizing gas breakdown waves in strong electric fields.

    Science.gov (United States)

    Klingbeil, R.; Tidman, D. A.; Fernsler, R. F.

    1972-01-01

    A previous analysis by Albright and Tidman (1972) of the structure of an ionizing potential wave driven through a dense gas by a strong electric field is extended to include atomic structure details of the background atoms and radiative effects, especially, photoionization. It is found that photoionization plays an important role in avalanche propagation. Velocities, electron densities, and temperatures are presented as a function of electric field for both negative and positive breakdown waves in nitrogen.

  1. Electrical breakdown of water using porous ceramic-coated electrode

    Czech Academy of Sciences Publication Activity Database

    Lukeš, Petr; Člupek, Martin; Babický, Václav; Šunka, Pavel

    Trondheim: IEEXplore, 2011. s. 140-140. ISBN 978-82-594-3525-5. [IEEE International Conference on Dielectric Liquids (ICDL 2011)/17./. 26.06.2011-30.06.2011, Trondheim] R&D Projects: GA AV ČR IAAX00430802 Institutional research plan: CEZ:AV0Z20430508 Keywords : non-thermal plasma * electrical discharge * water * electrical breakdown * surface chemistry Subject RIV: BL - Plasma and Gas Discharge Physics

  2. Partial Discharge Degradation and Breakdown Studies in Polypropylene Films

    OpenAIRE

    Thomas, Benny; Nema, RS

    1996-01-01

    Internal partial discharge characteristics are investigated on impregnated polypropylene films containing artificial cavity of well-defined dimensions, immersed in oil. Electrical breakdown studies are carried out at step-wise rising stress to evaluate constants of inverse power law model. Partial discharge pulse distribution patterns are acquired using PC interfaced multichannel analyser and statistical analysis of the discharge pulse spectrum is done by using 3-parameter Weibull distributio...

  3. Electrical breakdown of water using porous ceramic-coated electrode

    Czech Academy of Sciences Publication Activity Database

    Lukeš, Petr; Člupek, Martin; Babický, Václav; Šunka, Pavel

    NEW YORK : IEEE, 2011, P-126-P-126. ISBN 978-1-4244-7355-7. [IEEE International Conference on Dielectric Liquids (ICDL 2011)/17./. Trondheim (NO), 26.06.2011-30.06.2011] R&D Projects: GA AV ČR IAAX00430802 Institutional research plan: CEZ:AV0Z20430508 Keywords : non-thermal plasma * electrical discharge * water * electrical breakdown * surface chemistry Subject RIV: BL - Plasma and Gas Discharge Physics

  4. The Proactive International Dimension and the Breakdown of Authoritarian Regimes

    OpenAIRE

    Castaldo, Antonino

    2016-01-01

    There is international consensus among scholars that democratic transitions are multicausal processes in which both internal and international variables are involved (Pridham 1991, 1995; Whitehead 1996; Schmitter 1996; Linz and Stepan 1996; Carothers 1999; Morlino and Magen 2008; Grilli di Cortona 2009). This chapter is limited, on the one hand, to the dependent variable consisting solely of the crisis/breakdown/transformation of non-democratic regimes in the Third Wave o...

  5. The role of trust in communication breakdowns in disaster situations

    OpenAIRE

    Scholander, Robert

    2008-01-01

    Disaster situations are, by their very nature, broad and complex situations. While it is intrinsically appealing to assume that communication breakdowns in these situations are due to technological barriers, this assumption overlooks the possibility that non-technological barriers to communication exist within and between agencies and individuals. High levels of social capital within or between groups will enable better communication and resource flows. Thus trust will clearly have a critical...

  6. Breakdown of cell-collagen networks through collagen remodeling

    OpenAIRE

    Iordan, Andreea; Duperray, Alain; Gérard, Anaïs; Grichine, Alexei; Verdier, Claude

    2010-01-01

    International audience Collagen model tissues are analyzed, which consist of cells embedded in a collagen matrix at different concentrations (of cells and collagen). Rheological properties are measured and complementary confocal microscopy analyses are carried out. An important feature is observed, corresponding to the breakdown of the collagen network (i.e. decrease in network elasticity) for high collagen concentrations, due to the presence of cells. Thanks to confocal microscopy, we sho...

  7. Simulation of Ion Generation and Breakdown in Atmospheric Air

    OpenAIRE

    Zhang, W; Fisher, T. S.; Garimella, S V

    2004-01-01

    Understanding of ion generation in air provides insights to several applications, such as gas sensors, electrohydrodynamic pumping, and air purification. In this paper, ion generation processes in atmospheric air are simulated using a particle-in-cell and Monte Carlo method with emphasis on the prediction of ion generation and breakdown characteristics in microscale gaps. The simulation results are validated through comparison to Townsend’s discharge theory and experiments. The significance o...

  8. Schlieren imaging investigation of successive laser-induced breakdowns in atmospheric-pressure air

    Science.gov (United States)

    Bak, Moon Soo; Wermer, Lydia; Im, Seong-kyun

    2015-12-01

    Fast Schlieren imaging was performed to visualize the interactions between previously produced laser breakdown and a subsequent laser pulse. A pair of laser pulses was used to generate successive breakdowns in the quiescent standard air, and the interval between the pulses was varied from 50 ns to 100 μs to experimentally simulate various laser repetition rates. The incident laser energies ranged from 5 mJ to 31 mJ, and the energy absorbed by the breakdown of the second laser pulse was quantified by measuring the energies before and after the breakdown. The results indicate that the second laser pulse coupled to the background gas and produced a second laser breakdown only when the pulse interval was shorter than 250 ns or longer than 15 μs. For the shorter pulse intervals, the second breakdown occurred at the edge of the first breakdown region along the laser beam path, and its effect on the perturbation of the density field was found to be small. On the other hand, for the longer pulse intervals, the second breakdown occurred at the lens focal point, and the density field perturbations caused by the first and second breakdowns seemed to interact with each other inducing the Richtmyer-Mechkov instability. As a result, more significant turbulence in the density field was observed after successive laser pulse breakdowns than was observed following a single breakdown.

  9. On the assessment of extremely low breakdown probabilities by an inverse sampling procedure [gaseous insulation

    DEFF Research Database (Denmark)

    Thyregod, Poul; Vibholm, Svend

    1991-01-01

    First breakdown voltages obtained under the inverse sampling procedure assuming a double exponential flashover probability function are discussed. An inverse sampling procedure commences the voltage application at a very low level, followed by applications at stepwise increased levels until a...... breakdown occurs. Following a breakdown, the procedure is restarted at the initial level. The procedure is repeated until a predetermined number of breakdowns have occurred, and the average and standard deviation of the observed first breakdown levels are recorded. The authors derive the relation between...... the flashover probability function and the corresponding distribution of first breakdown voltages under the inverse sampling procedure, and show how this relation may be utilized to assess the single-shot flashover probability corresponding to the observed average first breakdown voltage. Since the...

  10. Improvement of powertrain efficiency through energy breakdown analysis

    International Nuclear Information System (INIS)

    Highlights: • Energy breakdown analysis for the vehicular powertrain. • Model for road vehicles simulation in different missions. • Implemented powertrain management strategies: intelligent gearbox, Stop and Start, free wheel. • Innovative hybrid powertrain turned to engine thermodynamic cycles minimization. • Evaluation of fuel savings associated to each management strategy. - Abstract: A vehicular powertrain can be thought as an energy conversion chain, each component being characterized by its efficiency. Significant global efficiency improvements can be achieved once is identified the system energy breakdown, individuating the losses connected to each powertrain component; it is then possible to carry out the most appropriate interventions. This paper presents a simulation study of a diesel-fuelled commercial vehicle powertrain based on the above summarized point of view. The work aims at individuating the energy flows involved in the system during different missions, proposing an intelligent combination of technical solutions which minimize fuel consumption. Through a validated Matlab–Simulink model, able to indicate the powertrain energy breakdown, simulations are carried out to evaluate the fuel saving associated to a series of powertrain management logics which lead to the minimization of engine losses, the recovery of reverse power in deceleration and braking, the elimination of useless engine cycles. Tests were performed for different real missions (urban, extra-urban and highway). The results obtained point out a –23% fuel consumption (average value for urban, extra-urban and highway missions) compared to the traditional powertrain. Clearly, such result affects positively the CO2 emission

  11. High Breakdown Strength, Multilayer Ceramics for Compact Pulsed Power Applications

    Energy Technology Data Exchange (ETDEWEB)

    Gilmore, B.; Huebner, W.; Krogh, M.L.; Lundstrom, J.M.; Pate, R.C.; Rinehart, L.F.; Schultz, B.C.; Zhang, S.C.

    1999-07-20

    Advanced ceramics are being developed for use in large area, high voltage devices in order to achieve high specific energy densities (>10 6 J/m 3 ) and physical size reduction. Initial materials based on slip cast TiO2 exhibited a high bulk breakdown strength (BDS >300 kV/cm) and high permittivity with low dispersion (e�100). However, strong area and thickness dependencies were noted. To increase the BDS, multilayer dielectric compositions are being developed based on glass/TiO2 composites. The addition of glass increases the density (�99.8% theoretical), forms a continuous grain boundary phase, and also allows the use of high temperature processes to change the physical shape of the dielectric. The permittivity can also be manipulated since the volume fraction and connectivity of the glassy phase can be readily shifted. Results from this study on bulk breakdown of TiO2 multilayer structures with an area of 2cm 2 and 0.1cm thickness have measured 650 kV/cm. Furthermore, a strong dependence of breakdown strength and permittivity has been observed and correlated with microstructure and the glass composition. This paper presents the interactive effects of manipulation of these variables.

  12. Breakdown in vapors of alcohols: methanol and ethanol

    Science.gov (United States)

    Petrovic, Zoran Lj.; Sivos, Jelena; Skoro, Nikola; Maric, Dragana; Malovic, Gordana

    2014-10-01

    Breakdown data for vapors of the two simplest alcohols - methanol and ethanol - are presented. The breakdown is achieved between plan-parallel electrodes, where cathode is made of copper and anode is a thin film of platinum deposited on quartz window. Diameter of electrodes is 5.4 cm and electrode gap 1.1 cm. We compare breakdown voltages (Paschen curves) for methyl and ethyl alcohol in the pressure range 0.1--2 Torr. In both vapors, the pressure is kept well below the vapor pressure, to prevent formation of liquid droplets. For each point of Paschen curves corresponding axial profiles of emission are recorded by ICCD camera in visual part of the spectra. Axial intensity distributions reveal important processes of excitation. Both vapors show strong emission peak near the cathode at all pd values covered by measurements, which indicates that excitation by ions and fast neutrals play important role in the discharge. Preliminary spectrally resolved measurements of the discharge structure with optical filters show that dominantly emission comes from CH band at 431 nm. There is a very low intensity of H α emission detected in ethanol vapor at high E/N, while it is much stronger in methanol even at lower E/N. It is interesting to note that H α emission in methanol exhibits exponential increase of intensity from the cathode to the anode, so it comes mainly from excitation by electrons, not heavy particles. Supported by MESTD Projects ON171037 and III41011.

  13. Relativistic runaway breakdown in low-frequency radio

    Science.gov (United States)

    Füllekrug, Martin; Roussel-Dupré, Robert; Symbalisty, Eugene M. D.; Chanrion, Olivier; Odzimek, Anna; van der Velde, Oscar; Neubert, Torsten

    2010-01-01

    The electromagnetic radiation emitted by an electron avalanche beam resulting from relativistic runaway breakdown within the Earth's atmosphere is investigated. It is found from theoretical modeling with a computer simulation that the electron beam emits electromagnetic radiation which is characterized by consecutive broadband pulses in the low-frequency radio range from ˜10 to 300 kHz at a distance of ˜800 km. Experimental evidence for the existence of consecutive broadband pulses is provided by low-frequency radio observations of sprite-producing lightning discharges at a distance of ˜550 km. The measured broadband pulses occur ˜4-9 ms after the sprite-producing lightning discharge, they exhibit electromagnetic radiation which mainly spans the frequency range from ˜50 to 350 kHz, and they exhibit complex waveforms without the typical ionospheric reflection of the first hop sky wave. Two consecutive pulses occur ˜4.5 ms and ˜3 ms after the causative lightning discharge and coincide with the sprite luminosity. It is concluded that relativistic runaway breakdown within the Earth's atmosphere can emit broadband electromagnetic pulses and possibly generates sprites. The source location of the broadband pulses can be determined with an interferometric network of wideband low-frequency radio receivers to lend further experimental support to the relativistic runaway breakdown theory.

  14. Thermal Reversible Breakdown and Resistivity Switching in Hafnium Dioxide

    Directory of Open Access Journals (Sweden)

    N. Raghavan

    2012-03-01

    Full Text Available We present a model of thermal reversible breakdown via conductive filaments (CFs in hafnium dioxide (HfO2. These CFs appear as a result of electrical pretreatment of a metal/HfO2/metal (semiconductor nanostructure (MIM(S. The model is based on an assumption that the thermal reversible breakdown of a CF is due to of Joule heating displaying an exponential dependence of conductivity on temperature. The corresponding current-voltage characteristic and temperature of a CF in its middle and at the interface with an electrode are calculated taking into account the heat conduction equation and boundary conditions with heat dissipation via electrodes. It is found that the current-voltage characteristic of a CF has three specific regions. The initial and final regions have turned out to be linear with respect to the current and display different slopes, while the middle region is characterized by both the S-shaped and ultralinear dependences which are affected by the ambient temperature and nanostructure parameters. The switching potential from the high resistivity state (HRS to the low resistivity state (LRS was shown to decrease with the ambient temperature and with worsening of heat dissipation conditions. We present a model of thermal reversible breakdown via conductive filaments (CFs in hafnium dioxide (HfO2. These CFs appear as a result of electrical pretreatment of a metal/HfO2/metal (semiconductor nanostructure (MIM(S. The model is based on an assumption that the thermal reversible breakdown of a CF is due to of Joule heating displaying an exponential dependence of conductivity on temperature. The corresponding current-voltage characteristic and temperature of a CF in its middle and at the interface with an electrode are calculated taking into account the heat conduction equation and boundary conditions with heat dissipation via electrodes. It is found that the current-voltage characteristic of a CF has three specific regions. The initial and

  15. PHENIX Work Breakdown Structure. Cost and schedule review copy

    Energy Technology Data Exchange (ETDEWEB)

    1994-02-01

    The Work Breakdown Structure (WBS) Book begins with this Overview section, which contains the high-level summary cost estimate, the cost profile, and the global construction schedule. The summary cost estimate shows the total US cost and the cost in terms of PHENIX construction funds for building the PHENIX detector. All costs in the WBS book are shown in FY 1993 dollars. Also shown are the institutional and foreign contributions, the level of pre-operations funding, and the cost of deferred items. Pie charts are presented at PHENIX WBS level 1 and 2 that show this information. The PHENIX construction funds are shown broken down to PHENIX WBS level 3 items per fiscal year, and the resulting profile is compared to the RHIC target profile. An accumulated difference of the two profiles is also shown. The PHENIX global construction schedule is presented at the end of the Overview section. Following the Overview are sections for each subsystem. Each subsystem section begins with a summary cost estimate, cost profile, and critical path. The total level 3 cost is broken down into fixed costs (M&S), engineering costs (EDIA) and labor costs. Costs are further broken down in terms of PHENIX construction funds, institutional and foreign contributions, pre-operations funding, and deferred items. Also shown is the contingency at level 3 and the level 4 breakdown of the total cost. The cost profile in fiscal years is shown at level 3. The subsystem summaries are followed by the full cost estimate and schedule sheets for that subsystem. These detailed sheets are typically carried down to level 7 or 8. The cost estimate shows Total, M&S, EDIA, and Labor breakdowns, as well as contingency, for each WBS entry.

  16. Asymmetric Bimodal Accelerator Cavity for Raising rf Breakdown Thresholds

    International Nuclear Information System (INIS)

    We consider an axisymmetric microwave cavity for an accelerator structure whose eigenfrequency for its second lowest TM-like axisymmetric mode is twice that of the lowest such mode, and for which the fields are asymmetric along its axis. In this cavity, the peak amplitude of the rf electric field that points into either longitudinal face can be smaller than the peak field which points out. Computations show that a structure using such cavities might support an accelerating gradient about 47% greater than that for a structure using similar single-mode cavities, without an increase in breakdown probability.

  17. Plasma temperature clamping in filamentation laser induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Harilal, Sivanandan S.; Yeak, J.; Phillips, Mark C.

    2015-10-19

    Ultrafast laser filament induced breakdown spectroscopy is a very promising method for remote material detection. We present characteristics of plasmas generated in a metal target by laser filaments in air. Our measurements show that the temperature of the ablation plasma is clamped along the filamentation channel due to intensity clamping in a filament. Nevertheless, significant changes in radiation intensity are noticeable, and this is essentially due to variation in the number density of emitting atoms. The present results also partly explains the reason for the occurrence of atomic plume during fs LIBS in air compared to long-pulse ns LIBS.

  18. Multi-harmonic RF test stand for RF breakdown studies

    International Nuclear Information System (INIS)

    A multi-harmonic RF test stand is under construction at Yale Beam Physics Laboratory. It includes a frequency multiplier which can generate high power harmonics efficiently that are phase locked to the fundamental drive frequency. In a bi-modal asymmetric cavity powered by this RF source, the cavity may experience reduced exposure time to peak fields and sweeping of peak fields across their surfaces, and strong asymmetry between surfaces that may experience cathode-and anode-like fields; these phenomena are to be assessed for their influence on RF breakdown probabilities.

  19. Electrical Breakdown Characteristic of Nanostructured W-Cu Contacts Materials

    Institute of Scientific and Technical Information of China (English)

    WANG Junbo; CHEN Wen'ge; DING Bingjun

    2006-01-01

    Nanostructured (NS) W- Cu composite powder was prepared by mechanical alloying ( MA ), and nanostructured bulk of W- Cu contact material was fabricated by hot press sintering in an electrical vacuum furnace. The microstructure, electric conductivity, hardness and break down voltage of NS W-Cu alloys were measured and compared to those of conventional W- Cu alloys prepared by powder metallurgy. The experimental results show that microstructural refinement and uniformity can improve the breakdown behavior and the electric arc stability of nanostructured W- Cu contacts materials. Also, the nanostructured W- Cu contact material shows the characteristic of spreading electric arcs, which is of benefit to electric arc erosion.

  20. Breakdown of 1D water wires inside Charged Carbon Nanotubes

    CERN Document Server

    Pant, Shashank

    2016-01-01

    Using Molecular Dynamics approach we investigated the structure, dynamics of water confined inside pristine and charged 6,6 carbon nanotubes (CNTs). This study reports the breakdown of 1D water wires and the emergence of triangular faced water on incorporating charges in 6,6 CNTs. Incorporation of charges results in high potential barriers to the flipping of water molecules due to the formation of a large number of hydrogen bonds. The PMF analyses show the presence of ~2 kcal/mol barrier for the movement of water inside pristine CNT and almost negligible barrier in charged CNTs.

  1. Breakdown of the Dipole Approximation in Strong-Field Ionization

    OpenAIRE

    Ludwig, A.; J. Maurer; MAYER, B.W.; Phillips, C. R.; Gallmann, L; Keller, U.

    2014-01-01

    We report the breakdown of the electric dipole approximation in the long-wavelength limit in strong-field ionization with linearly polarized few-cycle mid-infrared laser pulses at intensities on the order of 10$^{13}$ W/cm$^2$. Photoelectron momentum distributions were recorded by velocity map imaging and projected onto the beam propagation axis. We observe an increasing shift of the peak of this projection opposite to the beam propagation direction with increasing laser intensities. From a c...

  2. Thermally activated breakdown in a simple polymer model.

    Science.gov (United States)

    Fugmann, S; Sokolov, I M

    2010-03-01

    We consider the thermally activated fragmentation of a homopolymer chain. In our simple model the dynamics of the intact chain is a Rouse one until a bond breaks and bond breakdown is considered as a first passage problem over a barrier to an absorbing boundary. Using the framework of the Wilemski-Fixman approximation we calculate activation times of individual bonds for free and grafted chains. We show that these times crucially depend on the length of the chain and the location of the bond yielding a minimum at the free chain ends. Theoretical findings are qualitatively confirmed by Brownian dynamics simulations. PMID:20365762

  3. Thermally activated breakdown in a simple polymer model

    OpenAIRE

    Fugmann, S.; I. M. Sokolov

    2009-01-01

    We consider the thermally activated fragmentation of a homopolymer chain. In our simple model the dynamics of the intact chain is a Rouse one until a bond breaks and bond breakdown is considered as a first passage problem over a barrier to an absorbing boundary. Using the framework of the Wilemski-Fixman approximation we calculate activation times of individual bonds for free and grafted chains. We show that these times crucially depend on the length of the chain and the location of the bond ...

  4. Breakdown of the dipole approximation in strong-field ionization.

    Science.gov (United States)

    Ludwig, A; Maurer, J; Mayer, B W; Phillips, C R; Gallmann, L; Keller, U

    2014-12-12

    We report the breakdown of the electric dipole approximation in the long-wavelength limit in strong-field ionization with linearly polarized few-cycle mid-infrared laser pulses at intensities on the order of 10¹³ W/cm². Photoelectron momentum distributions were recorded by velocity map imaging and projected onto the beam propagation axis. We observe an increasing shift of the peak of this projection opposite to the beam propagation direction with increasing laser intensities. From a comparison with semiclassical simulations, we identify the combined action of the magnetic field of the laser pulse and the Coulomb potential as the origin of our observations. PMID:25541770

  5. Recovering from trust breakdowns in large system Implementations

    DEFF Research Database (Denmark)

    Schlichter, Bjarne Rerup; Andersen, Povl Erik Rostgård

    On the basis of experiences from the Faroese large-scale implementation of integrated healthcare information systems and insights into dynamic aspects of trust, we offer the following lessons learned for the successful management and recovery of trust (breakdowns) in large system implementations......: restore relations by turning towards face-to-face events and procedures, assure a well-functioning and available support organisation, demonstrate trust in actors to enhance their own self-confidence and celebrate successes, even the smallest or ones injected by yourself. The propositions are based on a 6...

  6. SPATIO-TEMPORAL ANALYSIS OF SWIRLING JET UNSTEADY BREAKDOWN

    Czech Academy of Sciences Publication Activity Database

    Uruba, Václav; Oberleithner, K.; Sieber, M.; Hladík, Ondřej

    Prague : Institute of Thermomechanics AS CR, v. v. i., 2010 - (Jonáš, P.; Uruba, V.), s. 29-30 ISBN 978-80-87012-27-7. [Colloquium Fluid Dynamics 2010. Praha (CZ), 20.10.2010-22.10.2010] R&D Projects: GA AV ČR(CZ) IAA200760614; GA ČR GA101/08/1112 Institutional research plan: CEZ:AV0Z20760514 Keywords : swirling jet * vortex breakdown * spatio-temporal analysis Subject RIV: BK - Fluid Dynamics

  7. Laser-Induced Breakdown Spectroscopy (LIBS): specific applications

    Science.gov (United States)

    Trtica, M. S.; Savovic, J.; Stoiljkovic, M.; Kuzmanovic, M.; Momcilovic, M.; Ciganovic, J.; Zivkovic, S.

    2015-12-01

    A short overview of Laser Induced Breakdown Spectroscopy (LIBS) with emphasis on the new trends is presented. Nowadays, due to unique features of this technique, LIBS has found applications in a great variety of fields. Achievements in the application of LIBS in nuclear area, for hazardous materials detection and in geology were considered. Also, some results recently obtained at VINCA Institute, with LIBS system based on transversely excited atmospheric (TEA) CO2 laser, are presented. Future investigations of LIBS will be oriented toward further improvement of the analytical performance of this technique, as well as on finding new application fields.

  8. Continuous breakdown of Purcell's scallop theorem with inertia

    CERN Document Server

    Lauga, Eric

    2007-01-01

    Purcell's scallop theorem defines the type of motions of a solid body - reciprocal motions - which cannot propel the body in a viscous fluid with zero Reynolds number. For example, the flapping of a wing is reciprocal and, as was recently shown, can lead to directed motion only if its frequency Reynolds number, Re_f, is above a critical value of order one. Using elementary examples, we show the existence of oscillatory reciprocal motions which are effective for all arbitrarily small values of the frequency Reynolds number and induce net velocities scaling as (Re_f)^\\alpha (alpha > 0). This demonstrates a continuous breakdown of the scallop theorem with inertia.

  9. Kinetic modeling of the Townsend breakdown in argon

    Science.gov (United States)

    Macheret, S. O.; Shneider, M. N.

    2013-10-01

    Kinetic modeling of the Townsend breakdown in argon was performed in the "forward-back" approximation. The kinetic model was found to adequately describe the left branch of the Paschen curve, and the important role of ionization by fast ions and atoms near the cathode, as well as the increase in secondary emission coefficient in strong electric fields described in the literature, was confirmed. The modeling also showed that the electron energy distribution function develops a beam of high-energy electrons and that the runaway effect, i.e., the monotonic increase of the mean electron energy with the distance from the cathode, occurs at the left branch of the Paschen curve.

  10. Chemical consequences of laser-induced breakdown in molecular gases

    Czech Academy of Sciences Publication Activity Database

    Babánková, Dagmar; Civiš, Svatopluk; Juha, Libor

    2006-01-01

    Roč. 30, č. 2-3 (2006), s. 75-88. ISSN 0079-6727 R&D Projects: GA ČR GA203/06/1278; GA MŠk LC510; GA MŠk LC528; GA MŠk 1P04LA235 Institutional research plan: CEZ:AV0Z40400503; CEZ:AV0Z10100523 Keywords : laser spark * laser-induced dielectric breakdown * laser-plasma chemistry Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.500, year: 2006

  11. Progress in fieldable laser-induced breakdown spectroscopy (LIBS)

    Science.gov (United States)

    Miziolek, Andrzej W.

    2012-06-01

    In recent years there has been great progress in the Laser Induced Breakdown Spectroscopy (LIBS) technology field. Significant advances have been made both in fundamental and applied research as well as in data processing/chemometrics. Improvements in components, most notably lasers/optics and spectrometers are enabling the development of new devices that are suitable for field use. These new commercial devices recently released to the marketplace, as well as ones currently under development, are bringing the potential of LIBS for CBRNE threat analysis into real-world applications.

  12. Biomedical and environmental applications of laser-induced breakdown spectroscopy

    Indian Academy of Sciences (India)

    V K Unnikrishnan; K S Choudhari; Suresh D Kulkarni; Rajesh Nayak; V B Kartha; C Santhosh; B M Suri

    2014-02-01

    Laser-induced breakdown spectroscopy (LIBS) is an emerging analytical technique with numerous advantages such as rapidity, multi-elemental analysis, minimal sample preparation, minimal destruction, low cost and versatility of being applied to a wide range of materials. In this paper, we report the preliminary observations we obtained using LIBS for clinical and environmental samples. Elemental analysis has been done qualitatively in human teeth samples which show encouraging results. It has also been demonstrated in this paper that LIBS can be very well utilized in field applications such as plastic waste sorting and recycling.

  13. Laser induced breakdown spectroscopy (LIBS) applied to plutonium analysis

    International Nuclear Information System (INIS)

    A Laser Induced Breakdown Spectroscopy (LIBS) system has been developed specifically for the quantitative analysis of gallium in plutonium dioxide in support of the MOX fuel development program. The advantage of this system is no sample preparation and the capability to analyze extremely small samples. Success in this application has prompted an expansion of the technique to other areas, including determination of plutonium isotopic ratios. This paper will present recent results for gallium content in PuO2 after processing via thermally induced gallium removal (TIGR). Data will also be presented for the determination of the plutonium 239/240 isotopic ratio

  14. Individual breakdown of pension rights and end of contract

    CERN Multimedia

    2015-01-01

    As in previous years, members of the CERN Pension Fund will shortly receive their “Individual breakdown of pension rights” by e-mail.   In this respect, we would like to remind members that according to Articles II 1.11 - II 1.12 (calculation and payment of the transfer value) and II 2.02 (retirement pension), several options are possible at the end of their contract (depending on their length of service in the Fund): payment of the transfer value into a personal bank account, payment of the transfer value into a new pension scheme, pension (deferred, anticipated or retirement). Benefits Service CERN Pension Fund

  15. Laser induced breakdown spectroscopy stratigraphic characterization of multilayered painted surfaces

    Science.gov (United States)

    Staicu, A.; Apostol, I.; Pascu, A.; Iordache, I.; Damian, V.; Pascu, M. L.

    2012-08-01

    Laser spectroscopy techniques are modern and competitive methods for elemental analysis. Laser induced breakdown spectroscopy (LIBS), due to its advantages as minimally invasive method that provides real time monitoring and selectivity, is a suitable tool to analyze sample composition. Based on the known emission spectra of heavy metals such as Pb, Zn, Au, Ca, a stratigraphic study regarding the identification of the painting layers content of different mock-up samples was performed. LIBS was used to monitor the laser induced stepwise selective removal of the painting layers and to analyze their composition. The obtained LIBS spectra were correlated with profilometric measurements.

  16. Experimental study of DC vacuum breakdown and application to high-gradient accelerating structures for CLIC

    CERN Document Server

    Shipman, Nicholas; Jones, Roger

    2016-01-01

    The compact linear collider (CLIC) is a leading candidate for the next generation high energy linear collider. As any breakdown would result in a partial or full loss of luminosity for the pulse in which it occurs, obtaining a low breakdown rate in CLIC accelerating structures is a critical requirement for the successful operation of the proposed collider. This thesis presents investigations into the breakdown phenomenon primarily in the low breakdown rate regime of interest to CLIC, performed using the CERN DC spark systems between 2011 and 2014. The design, construction and commissioning of several new pieces of hardware, as well as the development of improved techniques to measuring the inter-electrode gap distance are detailed. These hardware improvements were fundamental in enabling the exciting new experiments mentioned below, which in turn have provided significant additional insight into the phenomenon of breakdown. Experiments were performed to measure fundamental parameters of individual breakdowns...

  17. A possible new mechanism involved in non-uniform field breakdown in gaseous dielectrics

    International Nuclear Information System (INIS)

    The electrical breakdown of gases under uniform field conditions is fairly well understood in terms of the Townsend's breakdown theory. In most cases involving uniform fields, the breakdown voltage can be estimated via this theory using basic electron impact parameters for molecules in their ground electronic states. In contrast, a consistent model of gaseous breakdown under nonuniform fields is not available at present although substantial progress has been made recently. We point out the possibility that electron impact processes involving high-lying electronically-excited states may play a significant role under non-uniform field conditions. Thus, such processes may need to be included in order to obtain a better understanding of non-uniform field breakdown phenomena. The general, breakdown characteristics of highly non-uniform field gaps can be illustrated by that for a point-plane geometry. It has been found that the breakdown voltage for such a gap can be calculated by a simple streamer criterion if the pressure P, is above a critical value, Pc; for P c, the estimated breakdown voltage is found to coincide with the corona inception voltage, with the actual breakdown occurring at a higher voltage, corona discharges occur only for P c. In other words, the presence of corona in the pressure region below Pc seems to prevent the breakdown from occurring at the predicted value. This has led to the term ''corona stabilization'' to describe the enhancement in the breakdown voltage for pressures below Pc. Non-uniform field breakdown measurements in gases will be discussed. We will discuss the possibility that the ''corona stabilization'' is due to the prevention of avalanche progression by attachment of free electrons to molecules in their high-lying electronically-excited states. Information on electron attachment to electronically-excited states of molecules was not available up until the late 1980's

  18. A possible new mechanism involved in non-uniform field breakdown in gaseous dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Pinnaduwage, L.A.; Christophorou, L.G.

    1994-06-01

    The electrical breakdown of gases under uniform field conditions is fairly well understood in terms of the Townsend`s breakdown theory. In most cases involving uniform fields, the breakdown voltage can be estimated via this theory using basic electron impact parameters for molecules in their ground electronic states. In contrast, a consistent model of gaseous breakdown under nonuniform fields is not available at present although substantial progress has been made recently. We point out the possibility that electron impact processes involving high-lying electronically-excited states may play a significant role under non-uniform field conditions. Thus, such processes may need to be included in order to obtain a better understanding of non-uniform field breakdown phenomena. The general, breakdown characteristics of highly non-uniform field gaps can be illustrated by that for a point-plane geometry. It has been found that the breakdown voltage for such a gap can be calculated by a simple streamer criterion if the pressure P, is above a critical value, P{sub c}; for P < P{sub c}, the estimated breakdown voltage is found to coincide with the corona inception voltage, with the actual breakdown occurring at a higher voltage, corona discharges occur only for P < P{sub c}. In other words, the presence of corona in the pressure region below P{sub c} seems to prevent the breakdown from occurring at the predicted value. This has led to the term ``corona stabilization`` to describe the enhancement in the breakdown voltage for pressures below P{sub c}. Non-uniform field breakdown measurements in gases will be discussed. We will discuss the possibility that the ``corona stabilization`` is due to the prevention of avalanche progression by attachment of free electrons to molecules in their high-lying electronically-excited states. Information on electron attachment to electronically-excited states of molecules was not available up until the late 1980`s.

  19. Breakdown in the Organ Donation Process and Its Effect on Organ Availability

    OpenAIRE

    Manik Razdan; Degenholtz, Howard B.; Kahn, Jeremy M; Julia Driessen

    2015-01-01

    Background. This study examines the effect of breakdown in the organ donation process on the availability of transplantable organs. A process breakdown is defined as a deviation from the organ donation protocol that may jeopardize organ recovery. Methods. A retrospective analysis of donation-eligible decedents was conducted using data from an independent organ procurement organization. Adjusted effect of process breakdown on organs transplanted from an eligible decedent was examined using mul...

  20. Breakdown in hydrogen and deuterium gases in static and radio-frequency fields

    International Nuclear Information System (INIS)

    We report the results of a combined experimental and modeling study of the electrical breakdown of hydrogen and deuterium in static (DC) and radio-frequency (RF) (13.56 MHz) electric fields. For the simulations of the breakdown events, simplified models are used and only electrons are traced by Monte Carlo simulation. The experimental DC Paschen curve of hydrogen is used for the determination of the effective secondary electron emission coefficient. A very good agreement between the experimental and the calculated RF breakdown characteristics for hydrogen is found. For deuterium, on the other hand, presently available cross section sets do not allow a reproduction of RF breakdown characteristics

  1. Direct current breakdown in gases for complex geometries from high vacuum to atmospheric pressure

    International Nuclear Information System (INIS)

    The demand for improved performances of power transmission devices requires ever smaller dimensions and higher working voltages which lead to increased risk of breakdown, for example, in satellite slip rings. Previous works are mostly limited to breakdown in simple geometries such as parallel plates or pin to plate. Here we discuss the effect of more complex geometries for dc breakdown in gases over a large pressure range (2 × 10−5 to 103 mbar). Experimental measurements of dc gas discharge breakdown in a ring assembly geometry are compared with a numerical simulation model for gas breakdown using a fluid model. Starting with parallel plates (1 and 100 mm gap width representing approximately the shortest and longest electric field path lengths in the ring assembly geometry) and extending to double gap and multi-gap geometries, an understanding of the overall shape of the breakdown voltage versus pressure curve is established. The high (low) pressure thresholds of gas discharge are determined by the shortest (longest) electric field path length in a complex geometry. Moreover, the availability of multiple path lengths leads to a breakdown voltage minimum over a wide range of intermediate pressure because breakdown can occur in the most favourable gap. Finally, the numerical simulation in the ring assembly shows the importance of parameters such as the secondary electron emission coefficient which play a major role in determining the breakdown voltage value. (paper)

  2. Breakdown in hydrogen and deuterium gases in static and radio-frequency fields

    CERN Document Server

    Korolov, I

    2015-01-01

    We report the results of a combined experimental and modeling study of the electrical breakdown of hydrogen and deuterium in static (DC) and radio-frequency (RF, 13.56 MHz) electric fields. For the simulations of the breakdown events, simplified models are used and only electrons are traced by Monte Carlo simulation. The experimental DC Paschen curve of hydrogen is used for the determination of the effective secondary electron emission coefficient. A very good agreement between the experimental and the calculated RF breakdown characteristics for hydrogen is found. For deuterium, on the other hand, presently available cross section sets do not allow a reproduction of RF breakdown characteristics.

  3. The research of breakdown structure and coding system for construction project

    Institute of Scientific and Technical Information of China (English)

    丁大勇; 金维兴; 李培

    2004-01-01

    Whether the breakdown structure and coding system of construction projects are reasonable or not determines to a large degree the pepfofmance level of the entire project management. We analyze in detail the similarities and differences of two kinds of decomposing methods classified by type of work and construction elements based on the discussion of international typical coding standards system designing. We then deduce the differential coefficient relation between project breakdown strueture(PBS) and work breakdown structure (WBS). At the same time we constitute a comprehensive construction project breakdown system including element code and type of work code and make a further schematic presentation of the implementation of the sysrem' s functions.

  4. Oxide thinning percolation statistical model for soft breakdown in ultrathin gate oxides

    Science.gov (United States)

    Chen, Ming-Jer; Kang, Ting-Kuo; Liu, Chuan-Hsi; Chang, Yih J.; Fu, Kuan-Yu

    2000-07-01

    An existing cell-based percolation model with parameter correlation can find its potential applications in assessing soft-breakdown (BD) statistics as long as the oxide thinning due to the localized physical damage near the SiO2/Si interface is accounted for. The resulting model is expressed explicitly with the critical trap number per cell nBD and the remaining oxide thickness tox' both as parameters. Reproduction of time-to-bimodal (soft- and hard-) breakdown statistical data from 3.3-nm-thick gate-oxide samples yields nBD of 3 and 4 for soft and hard breakdown, respectively. The extracted tox' of 1.0 nm for soft breakdown, plus the transition layer thickness of 0.5 nm in the model, is fairly comparable with literature values from current-voltage fitting. The dimension and area of the localized physically damaged region or percolation path (cell) are quantified as well. Based on the work, the origins of soft and hard breakdown are clarified in the following: (i) soft breakdown behaves intrinsically as hard breakdown, that is, they share the same defect (neutral trap) generation process and follow Poisson random statistics; (ii) both are independent events corresponding to different tox' requirements; and (iii) hard breakdown takes place in a certain path located differently from that for the first soft breakdown.

  5. Ozone breakdown of EDTA and NTA solutions. Final report

    International Nuclear Information System (INIS)

    This experimental study for breakdown of spent metal cleaning solvent solutions of ethylenediaminetetra acetic acid (EDTA) and nitrilotriacetate (NTA) was conducted under DOE contract DE-AC07-80ID12169. Objectives of the study were to release and recover metal ions which had been complexed by the EDTA and NTA. The metal ions used were iron, copper, nickel, zinc, cobalt and chromium. Breakdown of the chelating agents was accomplished by ozonation in an aqueous media using ozone and ultraviolet light. The study shows that the subject metal-chelant complexes are broken down by the mechanism and that 70 to 100% of the metal ions are precipitated and absorbed on the precipitated oxides by the action of ozone. The remaining ions can be removed by secondary treatment methods. The effect of initial solution pH was studied but indicated no effect on the final results. All solutions after treatment had a pH range of 7.5 to 9.0. At this pH level, iron, zinc, chromium III and copper precipitated. Chromium VI, nickel and cobalt appear to be carried down through absorption and co-precipitation mechanisms. This study proves the technical feasibility of this process. Further research is needed to determine optimum ozone rates and reactor design parameters

  6. Time-resolved shadowgraphy of optical breakdown in fused silica

    Science.gov (United States)

    Tran, K. A.; Grigorov, Y. V.; Nguyen, V. H.; Rehman, Z. U.; Le, N. T.; Janulewicz, K. A.

    2015-07-01

    Dynamics of a laser-induced optical breakdown in the bulk of fused silica initiated by a sub-nanosecond laser pulse of an energy fluence as high as 8.7 kJ/cm2 was investigated by using femtosecond time-resolved shadowgraphy. Plasma ignition, growth of the damaged region and accompanying hydrodynamic motion were recorded from the moment directly before the arrival of the driving laser pulse, in the time steps adapted to the rate of the occurring processes. The growth rate of the plasma channel, curvature radii and velocities of the wave fronts were extracted from the shadowgrams. It was found that the plasma channel develops with a supersonic velocity and the first observed shock front tends to transform itself from the initial bowl-like shape to the final spherical one characterising an acoustic wave. Appearance of multiple fronts accompanying the main shock front was registered and used in more detailed analysis of the optical breakdown dynamics in the transparent dielectrics.

  7. Electric circuit analysis for plasma breakdown in JT-60SA

    International Nuclear Information System (INIS)

    To obtain stable plasma breakdown and for designing the details of a power supply system in JT-60SA, a precise evaluation of the magnetic field performance using an accurate circuit analysis model has to be conducted. This evaluation should include AC/DC converters such as thyristor converters and a high voltage generation circuit which consists of a DC current interrupter and a resistor set. In this paper, the preparation procedure of the analysis model is presented. Using this modeling method, a circuit analysis including not only complex interactions but also nonlinear phenomenon can be performed. As one of the applications of it, a circuit analysis of the tokamak system JT-60SA is demonstrated using the PSIM code. Specifically, some circuit analysis results of plasma breakdown at t=0 - 60 ms are shown using an ideal voltage source and a thyristor converter model for comparison. Then, the voltage fluctuations of the generator (H-MG, 400 MVA) at plasma initiation and their influence are also described. (author)

  8. Sulfur isotope effects in the thermal breakdown of pyrite

    International Nuclear Information System (INIS)

    Pyrite was broken down with excess iron powder in glass tubes at 6000 and 4509C. The products were pyrrhotite in the pyrite zone and troilite in the iron powder zone. The accompanying isotope effects were very small. delta34S values for pyrrhotite and troilite were all within +- 0.5per mille of the initial pyrite, and in each run pyrrhotite was somewhat enriched in 34S relative to troilite. The delta34S values for the remaining pyrite were almost identical to those of the initial pyrite until the reaction was 80% complete. Pyrites of the more than 80% reaction were appreciably enriched in 34S, although the maximum enrichment observed was only +2.0per mille for the pyrite of the 99% reaction. Applying a Rayleigh distillation model, we obtained in instantaneous fractionation factor between the product (pyrrhotite plus troilite) and pyrite of only 0.9996. These results are in striking contrast to the large kinetik isotope effects previously found in the breakdown of pyrite to pyrrhotite and sulfur. The present small isotope effects may be interpreted as indicating that the kinetic isotope effect was significantly reduced by the introduction of iron powder which may have taken an essential part in the mechanism of pyrite breakdown, rather than that isotope equilibration took place among the coexisting sulfide phases. (orig.)

  9. Experimental breakdown of selected anodized aluminum samples in dilute plasmas

    Science.gov (United States)

    Grier, Norman T.; Domitz, Stanley

    1992-01-01

    Anodized aluminum samples representative of Space Station Freedom structural material were tested for electrical breakdown under space plasma conditions. In space, this potential arises across the insulating anodized coating when the spacecraft structure is driven to a negative bias relative to the external plasma potential due to plasma-surface interaction phenomena. For anodized materials used in the tests, it was found that breakdown voltage varied from 100 to 2000 volts depending on the sample. The current in the arcs depended on the sample, the capacitor, and the voltage. The level of the arc currents varied from 60 to 1000 amperes. The plasma number density varied from 3 x 10 exp 6 to 10 exp 3 ions per cc. The time between arcs increased as the number density was lowered. Corona testing of anodized samples revealed that samples with higher corona inception voltage had higher arcing inception voltages. From this it is concluded that corona testing may provide a method of screening the samples.

  10. Laser induced breakdown spectroscopy inside liquids: Processes and analytical aspects

    Energy Technology Data Exchange (ETDEWEB)

    Lazic, V., E-mail: violeta.lazic@enea.it [ENEA (UTAPRAD-DIM), Via. E. Fermi 45, 00044 Frascati (RM) (Italy); Jovićević, S. [Institute of Physics, University of Belgrade, 11080 Belgrade (Serbia)

    2014-11-01

    This paper provides an overview of the laser induced breakdown spectroscopy (LIBS) inside liquids, applied for detection of the elements present in the media itself or in the submerged samples. The processes inherent to the laser induced plasma formation and evolution inside liquids are discussed, including shockwave generation, vapor cavitation, and ablation of solids. Types of the laser excitation considered here are single pulse, dual pulse and multi-pulse. The literature relative to the LIBS measurements and applications inside liquids is reviewed and the most relevant results are summarized. Finally, we discuss the analytical aspects and release some suggestions for improving the LIBS sensitivity and accuracy in liquid environment. - Highlights: • The paper reviews LIBS applications on bulk liquids and on submerged samples, using single, dual and multi pulse excitation. • The fundamentals about plasma in liquids are provided: beam transmission, breakdown, ablation, cavitation, and energy balance • Influence of the bubble’s optical properties on the plasma formation and detection after the second pulse is considered • The results obtained by various research groups and in different experimental conditions are reviewed and summarized • The analytical aspects are discussed, which include the experimental part, signal stability, data processing and calibration.

  11. Laser induced breakdown spectroscopy inside liquids: Processes and analytical aspects

    International Nuclear Information System (INIS)

    This paper provides an overview of the laser induced breakdown spectroscopy (LIBS) inside liquids, applied for detection of the elements present in the media itself or in the submerged samples. The processes inherent to the laser induced plasma formation and evolution inside liquids are discussed, including shockwave generation, vapor cavitation, and ablation of solids. Types of the laser excitation considered here are single pulse, dual pulse and multi-pulse. The literature relative to the LIBS measurements and applications inside liquids is reviewed and the most relevant results are summarized. Finally, we discuss the analytical aspects and release some suggestions for improving the LIBS sensitivity and accuracy in liquid environment. - Highlights: • The paper reviews LIBS applications on bulk liquids and on submerged samples, using single, dual and multi pulse excitation. • The fundamentals about plasma in liquids are provided: beam transmission, breakdown, ablation, cavitation, and energy balance • Influence of the bubble’s optical properties on the plasma formation and detection after the second pulse is considered • The results obtained by various research groups and in different experimental conditions are reviewed and summarized • The analytical aspects are discussed, which include the experimental part, signal stability, data processing and calibration

  12. Preliminary Breakdown: Physical Mechanisms and Potential for Energetic Emissions

    Science.gov (United States)

    Petersen, D.; Beasley, W. H.

    2014-12-01

    Observations and analysis of the preliminary breakdown phase of virgin negative cloud-to-ground (-CG) lightning strokes will be presented. Of primary interest are the physical processes responsible for the fast electric field "characteristic" pulses that are often observed during this phase. The pulse widths of characteristic pulses are shown to occur as a superposed bimodal distribution, with the short and long modes having characteristic timescales on the order of 1 microsecond and 10 microseconds, respectively. Analysis of these pulses is based on comparison with laboratory observations of long spark discharge processes and with recently acquired high-speed video observations of a single -CG event. It will be argued that the fast electric field bimodal distribution is the result of conventional discharge processes operating in an extensive strong ambient electric field environment. An important related topic will also be discussed, where it will be argued that preliminary breakdown discharges are capable of generating energetic electrons and may therefore seed relativistic electron avalanches that go on to produce pulsed energetic photon emissions.

  13. Breakdown Behavior of a Wireless Communication Network Under UWB Impact

    Science.gov (United States)

    Rohe, M.; Koch, M.

    Systems with high priority to safety and reliability such as monitoring systems on airports have to work properly. Fast information transmission, continuous access to databases, as well as the management of air traffic are most important for effective and safe operation. Sources of Intentional Electromagnetic Interference can be manufactured relatively easy using commercially available components by civilian persons with relevant expertise and can be used for sabotage or blackmail purposes. For analyzing the weak points of a system existing on airports, it is necessary to reproduce its setup. In this investigation a UHF transmitter of a wireless communication device is developed and its breakdown behavior to unipolar fast rise pulses (UWB) is determined. A breakdown is a non-permanent damage, but includes a type of upset, that requires manual reset or at least stops communications for some period of time. The transmitter consists of three main components connected by data cables: power supply, microcontroller, and loop antenna. The immunity tests are accomplished as a function of the electromagnetic field direction to the device using an open TEM waveguide.

  14. Rf breakdown studies in room temperature electron linac structures

    International Nuclear Information System (INIS)

    This paper is an overall review of studies carried out by the authors and some of their colleagues on RF breakdown, Field Emission and RF processing in room temperature electron linac structure. The motivation behind this work is twofold: in a fundamental way, to contribute to the understanding of the RF breakdown phenomenon, and as an application, to determine the maximum electric field gradient that can be obtained and used safely in future e/sup +-/ linear colliders. Indeed, the next generation of these machines will have to reach into the TeV (1012 eV) energy range, and the accelerating gradient will be to be of the crucial parameters affecting their design, construction and cost. For a specified total energy, the gradient sets the accelerator length, and once the RF structure, frequency and pulse repetition rate are selected, it also determines the peak and average power consumption. These three quantities are at the heart of the ultimate realizability and cost of these accelerators. 24 refs., 19 figs., 4 tabs

  15. A Photographic Atlas of Rock Breakdown Features in Geomorphic Environments

    Science.gov (United States)

    Bourke, Mary C. (Editor); Brearley, J. Alexander; Haas, Randall; Viles, Heather A.

    2007-01-01

    A primary goal of geomorphological enquiry is to make genetic associations between process and form. In rock breakdown studies, the links between process, inheritance and lithology are not well constrained. In particular, there is a need to establish an understanding of feature persistence. That is, to determine the extent to which in situ rock breakdown (e.g., aeolian abrasion or salt weathering) masks signatures of earlier geomorphic transport processes (e.g., fluvial transport or crater ejecta). Equally important is the extent to which breakdown during geomorphic transport masks the imprint of past weathering. The use of rock features in this way raises the important question: Can features on the surface of a rock reliably indicate its geomorphic history? This has not been determined for rock surfaces on Earth or other planets. A first step towards constraining the links between process, inheritance, and morphology is to identify pristine features produced by different process regimes. The purpose of this atlas is to provide a comprehensive image collection of breakdown features commonly observed on boulders in different geomorphic environments. The atlas is intended as a tool for planetary geoscientists and their students to assist in identifying features found on rocks on planetary surfaces. In compiling this atlas, we have attempted to include features that have formed 'recently' and where the potential for modification by another geomorphic process is low. However, we acknowledge that this is, in fact, difficult to achieve when selecting rocks in their natural environment. We group breakdown features according to their formative environment and process. In selecting images for inclusion in the atlas we were mindful to cover a wide range of climatic zones. For example, in the weathering chapter, clast features are shown from locations such as the hyper-arid polar desert of Antarctica and the semi-arid canyons of central Australia. This is important as some

  16. Comparison of laser induced breakdown spectroscopy and spark induced breakdown spectroscopy for determination of mercury in soils

    International Nuclear Information System (INIS)

    Mercury is a toxic element found throughout the environment. Elevated concentrations of mercury in soils are quite hazardous to plants growing in these soils and also the runoff of soils to nearby water bodies contaminates the water, endangering the flora and fauna of that region. This makes continuous monitoring of mercury very essential. This work compares two potential spectroscopic methods (laser induced breakdown spectroscopy (LIBS) and spark induced breakdown spectroscopy (SIBS)) at their optimum experimental conditions for mercury monitoring. For LIBS, pellets were prepared from soil samples of known concentration for generating a calibration curve while for SIBS, soil samples of known concentration were used in the powder form. The limits of detection (LODs) of Hg in soil were calculated from the Hg calibration curves. The LOD for mercury in soil calculated using LIBS and SIBS is 483 ppm and 20 ppm, respectively. The detection range for LIBS and SIBS is discussed. - Highlights: • We compared SIBS and LIBS for mercury (Hg) measurements in soil. • Hg 546.07 nm line was selected for both LIBS and SIBS measurements. • Limit of detection for Hg was found to be 20 ppm with SIBS and 483 ppm with LIBS

  17. The electrical breakdown strength of pre-stretched elastomers, with and without sample volume conservation

    DEFF Research Database (Denmark)

    Zakaria, Shamsul Bin; Morshuis, Peter H. F.; Yahia, Benslimane Mohamed; Yu, Liyun; Skov, Anne Ladegaard

    2015-01-01

    electro-mechanical failure mechanism. A thorough understanding of the mechanisms behind the electro-mechanical breakdown process is required for developing reliable transducers. In this study, two experimental configurations were used to determine the stretch dependence of the electrical breakdown...

  18. Vortex Breakdown Generated by off-axis Bifurcation in a cylinder with rotating covers

    DEFF Research Database (Denmark)

    Bisgaard, Anders; Brøns, Morten; Sørensen, Jens Nørkær

    2006-01-01

    Vortex breakdown of bubble type is studied for the flow in a cylinder with rotating top and bottom covers. For large ratios of the angular velocities of the covers, we observe numerically that the vortex breakdown bubble in the steady regime may occur through the creation of an off-axis vortex ring...

  19. Electronic individual breakdown of pension rights and/or transfer value

    CERN Multimedia

    Pension Fund

    2011-01-01

    Commencing this year, members of the personnel will be notified by e-mail of their annual breakdown of pension rights and/or transfer value. Each person receiving the e-mail notification will be invited to consult this breakdown by clicking on a link protected by AISlogin and a password. Benefits Service of the Pension Fund pension-benefits@cern.ch  

  20. Lowering effect of radioactive irradiation on breakdown voltage and electron avalanche pulse characteristics

    International Nuclear Information System (INIS)

    In the time resolving measurement of the growing process and breakdown of electron avalanche in a gap of uniform electric field, the phenomenon that DC breakdown voltage slightly lowered was observed when β ray was irradiated as the initial electron source, as compared with unirradiated condition. Beta source used is 90Sr-90Y of 2 mCi in radiative equilibrium. The experimental results and the examination are described in detail. In brief, the remarkable superposition of succeeding avalanche pulse over the preceeding avalanche pulse waveform was observed under the gap condition in which the breakdown voltage decreased in β-ray irradiation. Thus this superposition of avalanche pulses is considered as one of the causes of the breakdown voltage reduction. When β source is used as the initial electron source, the number of supplied initial electrons is very large as compared with unity, and at the same time, a great number of initial electrons can be supplied within the diffusion radius r of avalanche. Then the effect of initial electron number n0 was considered by employing a diagram for breakdown scheme. The transition from Townsend type breakdown to streamer type breakdown occurs owing to increasing n0, and in that condition, the breakdown voltage lowers slightly. (Wakatsuki, Y)

  1. In-situ optical breakdown: studies for a large CO2 laser amplifier

    International Nuclear Information System (INIS)

    We study optical breakdown from target reflected optical pulses in the Gemini laser system. We measure the retropulse fluence (or illuminance) leaving the amplifier in terms of the energy entering the breakdown region and find qualitative agreement but no quantitative agreement with theory. Particulates were observed on nucleopore filters through which gas samples were drawn

  2. In-situ optical breakdown: studies for a large CO/sub 2/ laser amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, C.J.; Bjurstrom, R.G.; Carpenter, J.P.; Coffelt, E.L.; Hayden, J.J.; Hebron, D.E.; McLeod, J.; Romero, V.

    1981-01-01

    We study optical breakdown from target reflected optical pulses in the Gemini laser system. We measure the retropulse fluence (or illuminance) leaving the amplifier in terms of the energy entering the breakdown region and find qualitative agreement but no quantitative agreement with theory. Particulates were observed on nucleopore filters through which gas samples were drawn.

  3. In-situ optical breakdown: Studies for a large CO2 laser amplifier

    Science.gov (United States)

    Elliott, C. J.; Bjurstrom, R. G.; Carpenter, J. P.; Coffelt, E. L.; Hayden, J. J.; Hebron, D. E.; McLeod, J.; Romero, V.

    Optical breakdown from target reflected optical pulses in the Gemini laser system was studied. The retropulse fluence (or illuminance) leaving the amplifier was measured in terms of the energy entering the breakdown region and qualitative agreement but no quantitative agreement with theory was found. Particulates were observed on nucleopore filters through which gas samples were drawn.

  4. In Situ Optical Breakdown-Studies For A Large CO2 Laser Amplifier

    Science.gov (United States)

    Elliott, C. J.; Bjurstrom, R. G.; Carpenter, J. P.; Coffelt, E. L.; Hayden, J. J.; Hebron, D. E.; McLeod, J.; Romero, V.

    1981-12-01

    We study optical breakdown from target reflected optical pulses in the Gemini laser system. We measure the retropulse fluence (or illuminance) leaving the amplifier in terms of the energy entering the breakdown region and find qualitative agreement but no quantitative agreement with theory. Particulates were observed on nucleopore filters through which gas samples were drawn.

  5. THE ONSET OF ELECTRICAL BREAKDOWN IN DUST LAYERS: II. EFFECTIVE DIELECTRIC CONSTANT AND LOCAL FIELD ENHANCEMENT

    Science.gov (United States)

    Part 1 of the work has shown that electrical breakdown in dust layers obeys Paschen's Law, but occurs at applied field values which appear too small to initiate the breakdown. In this paper the authors show how an effective dielectric constant characterizing the dust layer can be...

  6. Gas breakdown limit and maximum acceleration gradient for inverse Cherenkov laser accelerator

    CERN Document Server

    Liu, Y; Cline, D

    1999-01-01

    Laser intensity thresholds for CO sub 2 laser-induced gas breakdown, such as tunneling, multiphoton, and cascade ionization have been estimated for the inverse Cherenkov accelerator experiment at the Brookhaven Accelerator Test Facility. The gas breakdown is dominated by cascade ionization and the maximum acceleration gradient is up to 300 MeV/m for a 3 ps CO sub 2 laser.

  7. Electron transfer through time dependent bridges: Differences between Franck-Condon and Born-Oppenheimer breakdown

    International Nuclear Information System (INIS)

    We consider tunneling-mediated electron transfer through time dependent bridges. An approach is developed for computing corrections to the time dependent tunneling matrix element that arise from the breakdown of the Born-Oppenheimer Adiabatic approximation. Differences between Franck-Condon and Born-Oppenheimer breakdown are discussed in the context of bridge-mediated tunneling

  8. Scaling law for direct current field emission-driven microscale gas breakdown

    International Nuclear Information System (INIS)

    The effects of field emission on direct current breakdown in microscale gaps filled with an ambient neutral gas are studied numerically and analytically. Fundamental numerical experiments using the particle-in-cell/Monte Carlo collisions method are used to systematically quantify microscale ionization and space-charge enhancement of field emission. The numerical experiments are then used to validate a scaling law for the modified Paschen curve that bridges field emission-driven breakdown with the macroscale Paschen law. Analytical expressions are derived for the increase in cathode electric field, total steady state current density, and the ion-enhancement coefficient including a new breakdown criterion. It also includes the effect of all key parameters such as pressure, operating gas, and field-enhancement factor providing a better predictive capability than existing microscale breakdown models. The field-enhancement factor is shown to be the most sensitive parameter with its increase leading to a significant drop in the threshold breakdown electric field and also to a gradual merging with the Paschen law. The proposed scaling law is also shown to agree well with two independent sets of experimental data for microscale breakdown in air. The ability to accurately describe not just the breakdown voltage but the entire pre-breakdown process for given operating conditions makes the proposed model a suitable candidate for the design and analysis of electrostatic microscale devices.

  9. The Role of Sphingomyelin Breakdown in Measles Virus Immunmodulation

    Directory of Open Access Journals (Sweden)

    Elita Avota

    2014-06-01

    Full Text Available Measles virus (MV efficiently causes generalized immunosuppression which accounts to a major extent for cases of measles-asscociated severe morbidity and mortality. MV infections alter many functions of antigen presenting cells (APC (dendritic cells (DCs and lymphocytes, yet many molecular targets of the virus remain poorly defined. Cellular interactions and effector functions of DCs and lymphocytes are regulated by surface receptors. Associating with other proteins involved in cell signaling, receptors form part of receptosomes that respond to and transmit external signals through dynamic interctions with the cytoskeleton. Alterations in the composition and metabolism of membrane sphingolipids have a substantial impact on both processes. In this review we focus on the regulation of sphingomyelinase activity and ceramide release in cells exposed to MV and discuss the immunosuppressive role of sphingomyelin breakdown induced by MV.

  10. Study of breakdown in an ablative pulsed plasma thruster

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Tiankun; Wu, Zhiwen; Liu, Xiangyang; Xie, Kan; Wang, Ningfei; Cheng, Yue [School of Aerospace Engineering, Beijing Institute of Technology, Beijing 100081 (China)

    2015-10-15

    Breakdown in ablative pulsed plasma thrusters (APPTs) must be studied in order to design new types of APPTs and measure particular parameters. In this paper, we studied a parallel-plate ablative pulsed plasma thruster that used a coaxial semiconductor spark plug. By operating the APPT about 500 times with various capacitor voltages and electrode gaps, we measured and analyzed the voltage of the spark plug, the voltage between the electrodes, and the discharge current. These experiments revealed a time delay (∼1–10 μs) between spark plug ignition and capacitor discharge, which may affect the performance of high-pulsing-rate (>10 kHz) and double-discharge APPTs, and the measurements of some of the APPT parameters. The delay time decreased as the capacitor voltage increased, and it increased with an increasing electrode gap and increasing number of ignitions. We explain our results through a simple theoretical analysis.

  11. Laser-induced breakdown spectroscopy fundamentals and applications

    CERN Document Server

    Noll, Reinhard

    2012-01-01

    This book is a comprehensive source of the fundamentals, process parameters, instrumental components and applications of laser-induced breakdown spectroscopy (LIBS). The effect of multiple pulses on material ablation, plasma dynamics and plasma emission is presented. A heuristic plasma modeling allows to simulate complex experimental plasma spectra. These methods and findings form the basis for a variety of applications to perform quantitative multi-element analysis with LIBS. These application potentials of LIBS have really boosted in the last years ranging from bulk analysis of metallic alloys and non-conducting materials, via spatially resolved analysis and depth profiling covering measuring objects in all physical states: gaseous, liquid and solid. Dedicated chapters present LIBS investigations for these tasks with special emphasis on the methodical and instrumental concepts as well as the optimization strategies for a quantitative analysis. Requirements, concepts, design and characteristic features of LI...

  12. Evidence of electric breakdown induced by bubbles in liquid argon

    CERN Document Server

    Bay, F; Murphy, S; Resnati, F; Rubbia, A; Sergiampietri, F; Wu, S

    2014-01-01

    We report on the results of a high voltage test in liquid argon in order to measure its dielectric rigidity. Under stable conditions and below the boiling point, liquid argon was found to sustain a uniform electric field of 100 kV/cm, applied in a region of 20 cm$^2$ area across 1 cm thick gap. When the liquid is boiling, breakdowns may occur at electric fields as low as 40 kV/cm. This test is one of the R&D efforts towards the Giant Liquid Argon Charge Imaging ExpeRiment (GLACIER) as proposed Liquid Argon Time Projection Chamber (LAr TPC) for the LBNO observatory for neutrino physics, astrophysics and nucleon decay searches.

  13. Degeneracy breakdown as a source of supernovae Ia

    CERN Document Server

    Clavelli, L

    2016-01-01

    We pursue the investigation of a model for sub-Chandrasekhar supernovae Ia explosions (SNIa) in which the energy stored in the Pauli tower is released to trigger a nuclear deflagration. The simplest physical model for such a degeneracy breakdown is a phase transition to an exactly supersymmetric state in which the scalar partners of protons, neutrons, and leptons become degenerate with the familiar fermions of our world as in the supersymmetric standard model with susy breaking parameters relaxed to zero. We focus on the ability of the susy phase transition model to fit the total SNIa rate as well as the delay time distribution of SNIa after the birth of a progenitor white dwarf. We also study the ejected mass distribution and its correlation with delay time. Finally, we discuss the expected SNIa remnant in the form of a black hole of Jupiter mass or lower and the prospects for detecting such remnants.

  14. Detection of early caries by laser-induced breakdown spectroscopy

    Science.gov (United States)

    Sasazawa, Shuhei; Kakino, Satoko; Matsuura, Yuji

    2015-07-01

    To improve sensitivity of dental caries detection by laser-induced breakdown spectroscopy (LIBS) analysis, it is proposed to utilize emission peaks in the ultraviolet. We newly focused on zinc whose emission peaks exist in ultraviolet because zinc exists at high concentration in the outer layer of enamel. It was shown that by using ratios between heights of an emission peak of Zn and that of Ca, the detection sensitivity and stability are largely improved. It was also shown that early caries are differentiated from healthy part by properly setting a threshold in the detected ratios. The proposed caries detection system can be applied to dental laser systems such as ones based on Er:YAG-lasers. When ablating early caries part by laser light, the system notices the dentist that the ablation of caries part is finished. We also show the intensity of emission peaks of zinc decreased with ablation with Er:YAG laser light.

  15. Breakdown of modulational approximations in multimode nonlinear interactions

    Science.gov (United States)

    Rizzato, Felipe; Iorra, Paulo; Marini, Samuel; Peter, Eduardo; Pakter, Renato; Chavez, Abraham

    2015-11-01

    The present work investigates the breakdown of the modulational approximation in a multimode extension of the three wave (triplet) nonlinear interaction. The modulational approach is accurate when the nonlinear wave coupling is weak, which causes amplitudes and phases to evolve slowly in time. We examine the types of dynamics arising when the coupling rises from very small to large values. At small couplings, when the modulational approach is valid, amplitude excursions are small and energy remains confined to the most unstable triplet subset of the multimode system. Above a critical value of the coupling, amplitude excursions abruptly become much larger and energy distributes more evenly among the active modes. Estimates for the critical coupling and relaxation times can be obtained with proper analysis of the most unstable triplet. CNPq (BR), FAPERGS (BR), AFOSR (USA, grant FA9550-12-1-0438).

  16. Breakdown of the classical description of a local system

    DEFF Research Database (Denmark)

    Eran, Kot; Grønbech-Jensen, Niels; Nielsen, Bo Melholt; Neergaard-Nielsen, Jonas Schou; Polzik, Eugene Simon; Sørensen, Anders Søndberg

    2012-01-01

    We provide a straightforward demonstration of a fundamental difference between classical and quantum mechanics for a single local system: namely, the absence of a joint probability distribution of the position x and momentum p. Elaborating on a recently reported criterion by Bednorz and Belzig...... breakdown of a classical description of the underlying state. Most importantly, the criterion used does not rely on quantum mechanics and can thus be used to demonstrate nonclassicality of systems not immediately apparent to exhibit quantum behavior. The criterion is directly applicable to any system...... [ Phys. Rev. A 83 052113 (2011)] we derive a simple criterion that must be fulfilled for any joint probability distribution in classical physics. We demonstrate the violation of this criterion using the homodyne measurement of a single photon state, thus proving a straightforward signature of the...

  17. Kertész line of thermally activated breakdown phenomena

    KAUST Repository

    Yoshioka, Naoki

    2010-11-12

    Based on a fiber bundle model we substantially extend the phase-transition analogy of thermally activated breakdown of homogeneous materials. We show that the competition of breaking due to stress enhancement and due to thermal fluctuations leads to an astonishing complexity of the phase space of the system: varying the load and the temperature a phase boundary emerges, separating a Griffith-type regime of abrupt failure analogous to first-order phase transitions from disorder dominated fracture where a spanning cluster of cracks emerges. We demonstrate that the phase boundary is the Kertész line of the system along which thermally activated fracture appears as a continuous phase transition analogous to percolation. The Kertész line has technological relevance setting the boundary of safe operation for construction components under high thermal loads. © 2010 The American Physical Society.

  18. Off-axis vortex breakdown in a shallow whirlpool

    Science.gov (United States)

    Herrada, Miguel A.; Shtern, Vladimir N.; López-Herrera, José María

    2013-06-01

    The off-axis emergence of vortex breakdown (VB) is revealed. The steady axisymmetric flow in a vertical sealed cylinder, which is partially filled with water and the rest is filled with air, is driven by the rotating bottom disk. The numerical simulations show that VB can emerge away from the rotation axis, interface, and walls. As the rotation intensifies, VB first develops in the water region. If the water height is less (larger) than nearly one half of the cylinder radius, VB emerges off (on) the axis. As the rotation further increases, the off-axis VB ring touches the interface and then a thin countercirculation layer develops in the air flow above the water VB domain. This two-fluid VB ring shrinks (it even disappears in a very shallow whirlpool) as the interface approaches the bottom disk.

  19. Laser induced breakdown spectroscopy for the discrimination of Candida strains.

    Science.gov (United States)

    Manzoor, S; Ugena, L; Tornero-Lopéz, J; Martín, H; Molina, M; Camacho, J J; Cáceres, J O

    2016-08-01

    The present study reports the evaluation of Laser Induced Breakdown Spectroscopy (LIBS) and Neural Networks (NN) for the discrimination of different strains of various species of Candida. This genus of yeast was selected due to its medical relevance as it is commonly found in cases of fungal infection in humans. Twenty one strains belonging to seven species of Candida were included in the study. Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS) was employed as a complementary technique to provide information about elemental composition of Candida cells. The use of LIBS spectra in combination with optimized NN models provided reliable discrimination among the distinct Candida strains with a high spectral correlation index for the samples analyzed, without any false positive or false negative. Therefore, this study indicates that LIBS-NN based methodology has the potential to be used as fast fungal identification or even diagnostic method. PMID:27216662

  20. Recognition of archaeological materials underwater by laser induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    The detection of different materials immersed in seawater has been studied by means of Laser Induced Breakdown Spectroscopy. The plasma emission was produced by a Q-Switched Nd:YAG laser operated at 1064 nm in a dual pulse mode. Different classes of materials potentially found in the undersea archaeological parks, such as iron, copper-based alloys, precious alloys, marble and wood have been examined. Data acquisition and processing were optimized for better signal control and in order to improve the detection threshold. In all the examined cases but wood, qualitative analysis was successful and allowed for the material recognition. The spectral features necessary to clearly distinguish marble materials from calcareous rocks have been also established. It was found that these characteristic spectral intervals could be also used for the recognition of sedimentary layers deposited on the underwater findings. Quantitative chemical analysis was also performed on submerged bronze samples, after generating calibration curves with standards of similar matrix composition

  1. Kinetic modeling of the Townsend breakdown in argon

    Energy Technology Data Exchange (ETDEWEB)

    Macheret, S. O.; Shneider, M. N. [Department of Mechanical and Aerospace Engineering, Princeton University, D-414 Engineering Quadrangle, Princeton, New Jersey 08544 (United States)

    2013-10-15

    Kinetic modeling of the Townsend breakdown in argon was performed in the “forward-back” approximation. The kinetic model was found to adequately describe the left branch of the Paschen curve, and the important role of ionization by fast ions and atoms near the cathode, as well as the increase in secondary emission coefficient in strong electric fields described in the literature, was confirmed. The modeling also showed that the electron energy distribution function develops a beam of high-energy electrons and that the runaway effect, i.e., the monotonic increase of the mean electron energy with the distance from the cathode, occurs at the left branch of the Paschen curve.

  2. Domain wall mobility, stability and Walker breakdown in magnetic nanowires

    Science.gov (United States)

    Mougin, A.; Cormier, M.; Adam, J. P.; Metaxas, P. J.; Ferré, J.

    2007-06-01

    We present an analytical calculation of the velocity of a single 180° domain wall in a magnetic structure with reduced thickness and/or lateral dimension under the combined action of an external applied magnetic field and an electrical current. As for the case of field-induced domain wall propagation in thick films, two motion regimes with different mobilities are obtained, below and far above the so-called Walker field. Additionally, for the case of current induced motion, a Walker-like current density threshold is defined. The threshold field and current density, stating the wall's internal structure stability, differ from those in thick films; both are reduced by the same geometrical demagnetising factor which accounts for the confinement. This points out the fact that the velocity dependence over an extended field/current range and the knowledge of the Walker breakdown are mandatory to draw conclusions about the phenomenological Gilbert damping parameter tuning the magnetisation dynamics.

  3. Laser-induced breakdown spectroscopy theory and applications

    CERN Document Server

    Perini, Umberto

    2014-01-01

    This book deals with the Laser-Induced Breakdown Spectroscopy (LIBS), a widely used atomic emission spectroscopy technique for elemental analysis of materials. It is based on the use of a high-power, short pulse laser excitation. The book is divided into two main sections: the first one concerning theoretical aspects of the technique, the second one describing the state of the art in applications of the technique in different scientific/technological areas. Numerous examples of state of the art applications provide the readers an almost complete scenario of the LIBS technique. The LIBS theoretical aspects are reviewed. The book helps the readers who are less familiar with the technique to understand the basic principles. Numerous examples of state of the art applications give an almost complete scenario of the LIBS technique potentiality. These examples of applications may have a strong impact on future industrial utilization. The authors made important contributions to the development of this field.

  4. Relativistic runaway breakdown in low-frequency radio

    DEFF Research Database (Denmark)

    Fullekrug, M.; Roussel-Dupre, R.; Symbalisty, E.M.D.;

    2011-01-01

    characterized by consecutive broadband pulses in the low-frequency radio range from similar to 10 to 300 kHz at a distance of similar to 800 km. Experimental evidence for the existence of consecutive broadband pulses is provided by low-frequency radio observations of sprite-producing lightning discharges at a...... distance of similar to 550 km. The measured broadband pulses occur similar to 4-9 ms after the sprite-producing lightning discharge, they exhibit electromagnetic radiation which mainly spans the frequency range from similar to 50 to 350 kHz, and they exhibit complex waveforms without the typical...... ionospheric reflection of the first hop sky wave. Two consecutive pulses occur similar to 4.5 ms and similar to 3 ms after the causative lightning discharge and coincide with the sprite luminosity. It is concluded that relativistic runaway breakdown within the Earth's atmosphere can emit broadband...

  5. EC wave plasma breakdown on GAMMA 10 device

    Energy Technology Data Exchange (ETDEWEB)

    Shidara, Hiroyuki, E-mail: shidara.hiroyuki@jaea.go.jp [Plasma Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577 (Japan); Nakashima, Yousuke; Imai, Tsuyoshi; Kariya, Tsuyoshi; Minami, Ryutaro; Ichimura, Makoto; Yoshikawa, Masayuki [Plasma Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577 (Japan)

    2011-10-15

    A plasma production experiment by using an Electron Cyclotron Resonant Heating (ECRH) system has successfully been carried out on the GAMMA 10 linear device. On the experiments, the plasma breakdown has been operated by and built up the temperature and the density by a single 28 GHz/200 kW ECRH system, instead of usual scheme of two plasma guns. We studied the parameter scans on gas feeding level, ECRH wave polarization and ECRH antenna position with 200 kW/10 ms ECRH pulse injection and relayed to the usual Ion Cyclotron Range of Frequency heating sequence. As the result of this preliminary experiment, we could achieve the same level parameters of electron density and diamagnetism, etc. as the usual operational plasma performance like as 5 x 10{sup 19} m{sup -2}/7 x 10{sup -7} Wb.

  6. Elemental analysis of slurry samples with laser induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    Direct analysis of wet slurry samples with laser induced breakdown spectroscopy (LIBS) is challenging due to problems of sedimentation, splashing, and surface turbulence. Also, water can quench the laser plasma and suppress the LIBS signal, resulting in poor sensitivity. The effect of water on LIBS spectra from slurries was investigated. As the water content decreased, the LIBS signal was enhanced and the standard deviation was reduced. To improve LIBS slurry analysis, dried slurry samples prepared by applying slurry on PVC coated slides were evaluated. Univariate and multivariate calibration was performed on the LIBS spectra of the dried slurry samples for elemental analysis of Mg, Si, and Fe. Calibration results show that the dried slurry samples give a good correlation between spectral intensity and elemental concentration.

  7. Laser-induced breakdown spectroscopy analysis of energetic materials

    Science.gov (United States)

    de Lucia, Frank C.; Harmon, Russell S.; McNesby, Kevin L.; Winkel, Raymond J.; Miziolek, Andrzej W.

    2003-10-01

    A number of energetic materials and explosives have been studied by laser-induced breakdown spectroscopy (LIBS). They include black powder, neat explosives such as TNT, PETN, HMX, and RDX (in various forms), propellants such as M43 and JA2, and military explosives such as C4 and LX-14. Each of these materials gives a unique spectrum, and generally the spectra are reproducible shot to shot. We observed that the laser-produced microplasma did not initiate any of the energetic materials studied. Extensive studies of black powder and its ingredients by use of a reference spectral library have demonstrated excellent accuracy for unknown identification. Finally, we observed that these nitrogen- and oxygen-rich materials yield LIBS spectra in air that have correspondingly different O:N peak ratios compared with air. This difference can help in the detection and identification of such energetic materials.

  8. Laser induced breakdown spectroscopy stratigraphic characterization of multilayered painted surfaces

    International Nuclear Information System (INIS)

    Laser spectroscopy techniques are modern and competitive methods for elemental analysis. Laser induced breakdown spectroscopy (LIBS), due to its advantages as minimally invasive method that provides real time monitoring and selectivity, is a suitable tool to analyze sample composition. Based on the known emission spectra of heavy metals such as Pb, Zn, Au, Ca, a stratigraphic study regarding the identification of the painting layers content of different mock-up samples was performed. LIBS was used to monitor the laser induced stepwise selective removal of the painting layers and to analyze their composition. The obtained LIBS spectra were correlated with profilometric measurements. - Highlights: ► LIBS was used to analyze heavy metals in mock-up painting samples. ► LIBS data are correlated with profilometric and optical microscopy measurements. ► Appropriate analysis parameters are provided for some materials used in painting.

  9. Time domain simulations of preliminary breakdown pulses in natural lightning

    CERN Document Server

    Carlson, B E; Bitzer, P; Christian, H

    2016-01-01

    Lightning discharge is a complicated process with relevant physical scales spanning many orders of magnitude. In an effort to understand the electrodynamics of lightning and connect physical properties of the channel to observed behavior, we construct a simulation of charge and current flow on a narrow conducting channel embedded in three-dimensional space with the time domain electric field integral equation, the method of moments, and the thin-wire approximation. The method includes approximate treatment of resistance evolution due to lightning channel heating and the corona sheath of charge surrounding the lightning channel. Focusing our attention on preliminary breakdown in natural lightning by simulating stepwise channel extension with a simplified geometry, our simulation reproduces the broad features observed in data collected with the Huntsville Alabama Marx Meter Array. Some deviations in pulse shape details are evident, suggesting future work focusing on the detailed properties of the stepping mecha...

  10. Radiation Effects on Breakdown Characteristics of Multi Guarded Devices

    CERN Document Server

    Da Rold, M; Bisello, D; Candelori, A; Da Re, A; Dalla Betta, Gian Franco; Paccagnella, A; Soncini, G; Verzellesi, G; Wheadon, R

    1997-01-01

    Multiguard structures are used in order to enhance the breakdown voltage of microstrip detectors. In this work we studied the electrical properties of devices designed in four different layouts on n-Si substrates, based on a central diode surrounded by various p+ and/or n+ floating rings. In particular we measured the main DC characteristics and we compared the experimental results with those simulated by a two-dimensional drift-diffusion computer model. Device noise was also measured for the central diode as a function of the applied voltage. We repeated all measurements after neutron and gamma irradiation, in view of the application of these devices to silicon microstrip detectors for future high energy physics experiments. For example at the LHC the level of radiation damage expected during the detector lifetime implies very high bias voltages for the detector operation. Multiguards can offer a solution, provided the optimisation of the design takes into account the radiation effects.

  11. Titanium monoxide spectroscopy following laser-induced optical breakdown

    International Nuclear Information System (INIS)

    This work investigates Titanium Monoxide (TiO) in ablation-plasma by employing laser-induced breakdown spectroscopy (LIBS) with 1 to 10 TW/cm2 irradiance, pulsed, 13 nanosecond, Q-switched Nd:YAG laser radiation at the fundamental wavelength of 1064 nm. The analysis of TiO is based on our first accurate determination of transition line strengths for selected TiO A-X, B-X, and E-X transitions, particularly TiO A-X γ and B-X γ′ bands. Electric dipole line strengths for the A3Φ-X3δ and B3Π-X3δ bands of TiO are computed. The molecular TiO spectra are observed subsequent to laser-induced breakdown (LIB). We discuss analysis of diatomic molecular spectra that may occur simultaneously with spectra originating from atomic species. Gated detection is applied to investigate the development in time of the emission spectra following LIB. Collected emission spectra allow one to infer micro-plasma parameters such as temperature and electron density. Insight into the state of the micro-plasma is gained by comparing measurements with predictions of atomic and molecular spectra. Nonlinear fitting of recorded and computed diatomic spectra provides the basis for molecular diagnostics, while atomic species may overlap and are simultaneously identified. Molecular diagnostic approaches similar to TiO have been performed for diatomic molecules such as AlO, C2, CN, CH, N2, NH, NO and OH.

  12. Dynamics of optical breakdown in air induced by single and double nanosecond laser pulses

    Science.gov (United States)

    Mahdieh, Mohammad Hossein; Akbari Jafarabadi, Marzieh

    2015-12-01

    In this paper, an optical breakdown in air induced by single and double nanosecond laser pulses was studied. A high power Nd:YAG laser beam was used for producing optical breakdown plasma in the air. The dynamics of breakdown plasma were studied using an optical probe beam. A portion of the laser beam was used, as the probe beam and was aligned to propagate (perpendicular to the pump beam) through the breakdown region. The transmission of the probe beam (through the breakdown region) was temporally measured for both single and double pulse irradiations. The results were used to describe the evolution of the induced plasma in both conditions. These results show that the plasma formation time and its absorptivity are strongly dependent on the single or double pulse configurations.

  13. Dynamics of optical breakdown in air induced by single and double nanosecond laser pulses

    International Nuclear Information System (INIS)

    In this paper, an optical breakdown in air induced by single and double nanosecond laser pulses was studied. A high power Nd:YAG laser beam was used for producing optical breakdown plasma in the air. The dynamics of breakdown plasma were studied using an optical probe beam. A portion of the laser beam was used, as the probe beam and was aligned to propagate (perpendicular to the pump beam) through the breakdown region. The transmission of the probe beam (through the breakdown region) was temporally measured for both single and double pulse irradiations. The results were used to describe the evolution of the induced plasma in both conditions. These results show that the plasma formation time and its absorptivity are strongly dependent on the single or double pulse configurations

  14. Experimental Study on the Dielectric Breakdown Voltage of the Insulating Oil Mixed with Magnetic Nanoparticles

    Science.gov (United States)

    Lee, Jong-Chul; Kim, Woo-Young

    In this study, we have measured the dielectric breakdown voltage of transformer oil-based nanofluids in accordance with IEC 156 standard and have investigated the dielectric breakdown performance with the application of an external magnetic field and different volume concentrations of magnetic nanoparticles. It is confirmed that the dielectric breakdown voltage of pure transformer oil is about 10 kV with a gap distance of 1 mm between electrodes. In the case of our transformer oil-based nanofluids with 0.08% magnetic nanoparticles in the fluid), the dielectric breakdown voltage is three times higher than that of pure transformer oil. Furthermore, when the external magnetic field is applied under the experimental vessel, the dielectric breakdown voltage of the nanofluids is above 40 kV, which is 30% higher than that without the external magnetic field.

  15. Electromechanical Breakdown of Barrier-Type Anodized Aluminum Oxide Thin Films Under High Electric Field Conditions

    Science.gov (United States)

    Chen, Jianwen; Yao, Manwen; Yao, Xi

    2016-02-01

    Barrier-type anodized aluminum oxide (AAO) thin films were formed on a polished aluminum substrate via electrochemical anodization in 0.1 mol/L aqueous solution of ammonium pentaborate. Electromechanical breakdown occurred under high electric field conditions as a result of the accumulation of mechanical stress in the film-substrate system by subjecting it to rapid thermal treatment. Before the breakdown event, the electricity of the films was transported in a highly nonlinear way. Immediately after the breakdown event, dramatic cracking of the films occurred, and the cracks expanded quickly to form a mesh-like dendrite network. The breakdown strength was significantly reduced because of the electromechanical coupling effect, and was only 34% of the self-healing breakdown strength of the AAO film.

  16. Study of predicting breakdown voltage of stator insulation in generator based on BP neural network

    Institute of Scientific and Technical Information of China (English)

    Jiang Yuao; Zhang Aide; Liu Libing; Du Yu; Gao Naikui; Peng Zongren

    2007-01-01

    The breakdown voltage plays an important role in evaluating residual life of stator insulation in generator. In this paper, we discussed BP neural network that was used to predict the breakdown voltage of stator insulation in generator of 300 MW/18 kV. At first the neural network has been trained by the samples that include the varieties of dielectric loss factor tanδ, the partial discharge parameters and breakdown voltage. Then we tried to predict the breakdown voltage of samples and stator insulations subjected to multi-stress aging by the trained neural network. We found that it's feasible and accurate to predict the voltage. This method can be applied to predict breakdown voltage of other generators which have the same insulation structure and material.

  17. Backside optimization for improving avalanche breakdown behavior of 4.5 kV IGBT

    International Nuclear Information System (INIS)

    The static avalanche breakdown behavior of 4.5 kV high-voltage IGBT is studied by theory analysis and experiment. The avalanche breakdown behaviors of the 4.5 kV IGBTs with different backside structures are investigated and compared by using the curve tracer. The results show that the snap back behavior of the breakdown waveform is related to the bipolar PNP gain, which leads to the deterioration of the breakdown voltage. There are two ways to optimize the backside structure, one is increasing the implant dose of the N+ buffer layer, the other is decreasing the implant dose of the P+ collector layer. It is found that the optimized structure is effective in suppressing the snap back behavior and improving the breakdown characteristic of high voltage IGBT. (paper)

  18. Gas Breakdown of Radio Frequency Glow Discharges in Helium at near Atmospheric Pressure

    Science.gov (United States)

    Liu, Xinkun; Xu, Jinzhou; Cui, Tongfei; Guo, Ying; Zhang, Jing; Shi, Jianjun

    2013-07-01

    A one-dimensional self-consistent fluid model was developed for radio frequency glow discharge in helium at near atmospheric pressure, and was employed to study the gas breakdown characteristics in terms of breakdown voltage. The effective secondary electron emission coefficient and the effective electric field for ions were demonstrated to be important for determining the breakdown voltage of radio frequency glow discharge at near atmospheric pressure. The constant of A was estimated to be 64±4 cm-1Torr-1, which was proportional to the first Townsend coefficient and could be employed to evaluate the gas breakdown voltage. The reduction in the breakdown voltage of radio frequency glow discharge with excitation frequency was studied and attributed to the electron trapping effect in the discharge gap.

  19. Backside optimization for improving avalanche breakdown behavior of 4.5 kV IGBT

    Science.gov (United States)

    Xiaoli, Tian; Jiang, Lu; Yuan, Teng; Wenliang, Zhang; Shuojin, Lu; Yangjun, Zhu

    2015-03-01

    The static avalanche breakdown behavior of 4.5 kV high-voltage IGBT is studied by theory analysis and experiment. The avalanche breakdown behaviors of the 4.5 kV IGBTs with different backside structures are investigated and compared by using the curve tracer. The results show that the snap back behavior of the breakdown waveform is related to the bipolar PNP gain, which leads to the deterioration of the breakdown voltage. There are two ways to optimize the backside structure, one is increasing the implant dose of the N+ buffer layer, the other is decreasing the implant dose of the P+ collector layer. It is found that the optimized structure is effective in suppressing the snap back behavior and improving the breakdown characteristic of high voltage IGBT. Project supported by the National Major Science and Technology Special Project of China (No. 2011ZX02503-003).

  20. Energetic high-voltage breakdowns in vacuum over a large gap for ITER neutral beam accelerator

    International Nuclear Information System (INIS)

    Highlights: ► We performed energetic high voltage breakdowns up to 370 kV with a stored energy of 1 kJ. ► No breakdowns at 200 kV could be produced over a gap of 85 mm using 100 cm2 copper electrodes. ► Electrodes damage was visible after the experiment. ► The number of arcs impacts is orders of magnitude above the number of breakdowns. -- Abstract: CEA has undertaken tests to study the resilience of copper electrodes in vacuum against energetic high-voltage breakdowns using external capacitors to provide the energy. Earlier tests succeeded in dissipating a maximum of 150 J in a 30 mm gap, limited by the equivalent series resistance (ESR) in the external capacitors. Using new ones with an ESR that is a factor of 10 lower it was unsuccessfully tried to produce breakdowns at 200 kV over the 85 mm gap, despite the use of a UV flash lamp and a “field enhancement ring” (FER) that locally increased the electric field on the cathode by 50%. Consequently, the breakdowns had to be produced by raising the voltage to 300–350 kV while maintaining the gap at 85 mm. During these tests, single breakdowns dissipated up to 1140 J in the 85 mm vacuum gap. Inspection of the electrodes revealed that substantial amounts of copper appear have been evaporated from the anode and deposited on to the cathode. Also electrode deconditioning occurred

  1. Effects of elevated temperature on protein breakdown in muscles from septic rats

    International Nuclear Information System (INIS)

    Elevated temperature has been proposed to contribute to accelerated muscle protein degradation during fever and sepsis. The present study examined the effect of increased temperature in vitro on protein turnover in skeletal muscles from septic and control rats. Sepsis was induced by cecal ligation and puncture (CLP); control rats were sham operated. After 16 h, the extensor digitorum longus (EDL) and soleus (SOL) muscles were incubated at 37 or 40 degrees C. Protein synthesis was determined by measuring incorporation of [14C]phenylalanine into protein. Total and myofibrillar protein breakdown was assessed from release of tyrosine and 3-methylhistidine (3-MH), respectively. Total protein breakdown was increased at 40 degrees C by 15% in EDL and by 29% in SOL from control rats, whereas 3-MH release was not affected. In muscles from septic rats, total and myofibrillar protein breakdown was increased by 22 and 30%, respectively, at 40 degrees C in EDL but was not altered in SOL. Protein synthesis was unaffected by high temperature both in septic and nonseptic muscles. The present results suggest that high temperature is not the primary mechanism of increased muscle protein breakdown in sepsis because the typical response to sepsis, i.e., a predominant increase in myofibrillar protein breakdown, was not induced by elevated temperature in normal muscle. It is possible, however, that increased temperature may potentiate protein breakdown that is already stimulated by sepsis because elevated temperature increased both total and myofibrillar protein breakdown in EDL from septic rats

  2. Positive and negative effects of dielectric breakdown in transformer oil based magnetic fluids

    International Nuclear Information System (INIS)

    The transformer oil based magnetic fluids can be considered as the next-generation insulation fluids because they offer exciting new possibilities to enhance dielectric breakdown voltage as well as heat transfer performance compared to pure transformer oils. In this study, we have investigated the dielectric breakdown strength of the fluids with the various volume concentrations of nanoparticles in accordance with IEC 156 standard and have tried to find the reason for changing the dielectric breakdown voltage of the fluids from the magnetic field analysis. It was found that the dielectric breakdown voltage of pure transformer oil is around 12 kV with the gap distance of 1.5 mm. In the case of our transformer oil-based magnetic fluids with 0.08% < Φ < 0.6% (Φ means the volume concentration of magnetic nanoparticles), the dielectric breakdown voltage shows above 40 kV, which is 3.3 times higher positively than that of pure transformer oil. Negatively in the case when the volume concentration of magnetic nanoparticles is above 0.65%, the dielectric breakdown voltage decreases reversely. From the magnetic field analysis, the reason might be considered as two situations: the positive is for the conductive nanoparticles dispersed well near the electrodes, which play an important role in converting fast electrons to slow negatively charged particles, and the negative is for the agglomeration of the particles near the electrodes, which leads to the breakdown initiation.

  3. CO2 laser breakdown and heating of hydrogen in a magnetic mirror field

    International Nuclear Information System (INIS)

    A 1-GW, 125-J CO2-laser pulse focussed by a 10-cm focal-length parabolic mirror has been used to induce breakdown and heating in 15-torr hydrogen along the axis of a short 50-kGauss magnetic mirror field. Evolution of the breakdown plasma thus produced has been studied by high-speed photography, ruby-laser Thomson scattering and a Mach-Zehnder interferometer. Results indicate an efficient radial confinement of plasma by the mirror field with an electron temperature much enhanced over that resulting from a field-free breakdown. An electron temperature of approximately 100 eV has been measured near the laser focus at the end of the gain-switched CO2-laser spike in the mirror field compared to approximately 20 eV at the same time in a field-free breakdown. Interferometric measurements show that breakdown results in a cylindrical plasma with an electron density minimum on axis in both cases. A monitor of the transmitted CO2-laser pulse indicates very incomplete coupling of laser radiation into the plasma column with the field applied, presumably because of fraction losses at the entrance boundary of the breakdown. Experimental results agree qualitatively at early times with a numerical hydrodynamic calculation which neglects axial plasma expansion and assumes complete coupling of the laser into the breakdown column. (author)

  4. Breakdown in the Organ Donation Process and Its Effect on Organ Availability

    Directory of Open Access Journals (Sweden)

    Manik Razdan

    2015-01-01

    Full Text Available Background. This study examines the effect of breakdown in the organ donation process on the availability of transplantable organs. A process breakdown is defined as a deviation from the organ donation protocol that may jeopardize organ recovery. Methods. A retrospective analysis of donation-eligible decedents was conducted using data from an independent organ procurement organization. Adjusted effect of process breakdown on organs transplanted from an eligible decedent was examined using multivariable zero-inflated Poisson regression. Results. An eligible decedent is four times more likely to become an organ donor when there is no process breakdown (adjusted OR: 4.01; 95% CI: 1.6838, 9.6414; P<0.01 even after controlling for the decedent’s age, gender, race, and whether or not a decedent had joined the state donor registry. However once the eligible decedent becomes a donor, whether or not there was a process breakdown does not affect the number of transplantable organs yielded. Overall, for every process breakdown occurring in the care of an eligible decedent, one less organ is available for transplant. Decedent’s age is a strong predictor of likelihood of donation and the number of organs transplanted from a donor. Conclusion. Eliminating breakdowns in the donation process can potentially increase the number of organs available for transplant but some organs will still be lost.

  5. Breakdown Voltage Research of Penning Gas Mixture in Plasma Display Panel

    Institute of Scientific and Technical Information of China (English)

    Guo Bingang; Liu Chunliang; Song Zhongxiao; Fan Yufeng; Xia Xing; Liu Liu; Fan Duowang

    2005-01-01

    Paschen law and equations, which ignore the influence of the Penning ionization on the electron ionization coefficient (α), are always used as the approximation of the breakdown voltage criterion of the Penning gas mixture in current researches of discharge characteristics of the plasma display panel (PDP). It is doubtful that whether their results match the facts. Based on the Townsend gas self-sustaining discharge condition and the chemical kinetics analysis of the Penning gas mixture discharging in PDP, the empirical equation to describe the breakdown of the Penning gas mixture is given. It is used to calculate the breakdown voltage curves of Ne-Xe/MgO and Ne-Ar/MgO in a testing macroscopic discharge cell of AC-PDP. The effective secondary electron emission coefficients (γeff) of the MgO protective layers are derived by comparing the breakdown voltage curves obtained from the empirical equation with the experimental data of breakdown voltages. In comparison with the results calculated by the Paschen law and the equation which ignore the influence of the Penning ionization on α , the results calculated by the empirical equation have better conformity with experimental data. The empirical equation characterizes the breakdown of the Penning gas mixture in PDP effectively, and gives a convenient way to study its breakdown characteristics and the secondary electron emission behaviors.

  6. Mask characterization for CDU budget breakdown in advanced EUV lithography

    Science.gov (United States)

    Nikolsky, Peter; Strolenberg, Chris; Nielsen, Rasmus; Nooitgedacht, Tjitte; Davydova, Natalia; Yang, Greg; Lee, Shawn; Park, Chang-Min; Kim, Insung; Yeo, Jeong-Ho

    2012-11-01

    As the ITRS Critical Dimension Uniformity (CDU) specification shrinks, semiconductor companies need to maintain a high yield of good wafers per day and a high performance (and hence market value) of finished products. This cannot be achieved without continuous analysis and improvement of on-product CDU as one of the main drivers for process control and optimization with better understanding of main contributors from the litho cluster: mask, process, metrology and scanner. In this paper we will demonstrate a study of mask CDU characterization and its impact on CDU Budget Breakdown (CDU BB) performed for an advanced EUV lithography with 1D and 2D feature cases. We will show that this CDU contributor is one of the main differentiators between well-known ArFi and new EUV CDU budgeting principles. We found that reticle contribution to intrafield CDU should be characterized in a specific way: mask absorber thickness fingerprints play a role comparable with reticle CDU in the total reticle part of the CDU budget. Wafer CD fingerprints, introduced by this contributor, may or may not compensate variations of mask CD's and hence influence on total mask impact on intrafield CDU at the wafer level. This will be shown on 1D and 2D feature examples in this paper. Also mask stack reflectivity variations should be taken into account: these fingerprints have visible impact on intrafield CDs at the wafer level and should be considered as another contributor to the reticle part of EUV CDU budget. We observed also MEEF-through-field fingerprints in the studied EUV cases. Variations of MEEF may also play a role for the total intrafield CDU and may be taken into account for EUV Lithography. We characterized MEEF-through-field for the reviewed features, the results to be discussed in our paper, but further analysis of this phenomenon is required. This comprehensive approach to characterization of the mask part of EUV CDU characterization delivers an accurate and integral CDU Budget

  7. Scaling and volatility of breakouts and breakdowns in stock price dynamics.

    Directory of Open Access Journals (Sweden)

    Lu Liu

    Full Text Available BACKGROUND: Because the movement of stock prices is not only ubiquitous in financial markets but also crucial for investors, extensive studies have been done to understand the law behind it. In particular, since the financial crisis in 2008, researchers have a more interest in investigating large market volatilities in order to grasp changing market trends. METHODOLOGY/PRINCIPAL FINDINGS: In this work, we analyze the breakouts and breakdowns of both the Standard & Poor's 500 Index in the US stock market and the Shanghai Composite Index in the Chinese stock market. The breakout usually represents an ongoing upward trend in technical analysis while the breakdown represents an ongoing downward trend. Based on the renormalization method, we introduce two parameters to quantize breakouts and breakdowns, respectively. We discover scaling behavior, characterized by power-law distributions for both the breakouts and breakdowns in the two financial markets with different power-law exponents, which reflect different market volatilities. In detail, the market volatility for breakdowns is usually larger than that for breakouts. Moreover, as an emerging market, the Chinese stock market has larger market volatilities for both the breakouts and breakdowns than the US stock market (a mature market. Further, the short-term volatilities show similar features for both the US stock market and the Chinese stock market. However, the medium-term volatilities in the US stock market are almost symmetrical for the breakouts and breakdowns, whereas those in the Chinese stock market appear to be asymmetrical for the breakouts and breakdowns. CONCLUSIONS/SIGNIFICANCE: The methodology presented here provides a way to understand scaling and hence volatilities of breakouts and breakdowns in stock price dynamics. Our findings not only reveal the features of market volatilities but also make a comparison between mature and emerging financial markets.

  8. Anomalous memory effect in the breakdown of low-pressure argon in a long discharge tube

    International Nuclear Information System (INIS)

    The characteristics of breakdown of argon in a long tube (with a gap length of 75 cm and diameter of 2.8 cm) at pressures of 1 and 5 Torr and stationary discharge currents of 5–40 mA were studied experimentally. The breakdown was initiated by paired positive voltage pulses with a rise rate of ∼108–109 V/s and duration of ∼1–10 ms. The time interval between pairs was varied in the range of Τ ∼ 0.1–1 s, and that between pulses in a pair was varied from τ = 0.4 ms to ≈Τ/2. The aim of this work was to detect and study the so-called “anomalous memory effect” earlier observed in breakdown in nitrogen. The effect consists in the dynamic breakdown voltage in the second pulse in a pair being higher than in the first pulse (in contrast to the “normal” memory effect, in which the relation between the breakdown voltages is opposite). It is found that this effect is observed when the time interval between pairs of pulses is such that the first pulse in a pair is in the range of the normal memory effect of the preceding pair (under the given conditions, Τ ≈ 0.1–0.4 s). In this case, at τ ∼ 10 ms, the breakdown voltage of the second pulse is higher than the reduced breakdown voltage of the first pulse. Optical observations of the ionization wave preceding breakdown in a long tube show that, in the range of the anomalous memory effect and at smaller values of τ, no ionization wave is detected before breakdown in the second pulse. A qualitative interpretation of the experimental results is given

  9. Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor

    International Nuclear Information System (INIS)

    Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14 μm. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7 μm gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed

  10. Measurements of electron avalanche formation time in W-band microwave air breakdown

    International Nuclear Information System (INIS)

    We present measurements of formation times of electron avalanche ionization discharges induced by a focused 110 GHz millimeter-wave beam in atmospheric air. Discharges take place in a free volume of gas, with no nearby surfaces or objects. When the incident field amplitude is near the breakdown threshold for pulsed conditions, measured formation times are ∼0.1-2 μs over the pressure range 5-700 Torr. Combined with electric field breakdown threshold measurements, the formation time data shows the agreement of 110 GHz air breakdown with the similarity laws of gas discharges.

  11. Multivariate Analysis of Laser-Induced Breakdown Spectroscopy for Discrimination between Explosives and Plastics

    International Nuclear Information System (INIS)

    A method to distinguish explosives from plastics using laser-induced breakdown spectroscopy is discussed. A model for classification with cross-validation theory is built based on the partial least-square discriminant analysis method. Seven types of plastics and one explosive are used as samples to test the model. The experimental results demonstrate that laser-induced breakdown spectroscopy has the capacity to discriminate explosives from plastics combined with chemometrics methods. The results could be useful for prospective research of laser-induced breakdown spectroscopy on the differentiation of explosives and other materials. (fundamental areas of phenomenology(including applications))

  12. JOINT INVESTIGATION OF ROTATING FLOW WITH VORTEX BREAKDOWN USING CFD, VISUALIZATION AND LDV

    Institute of Scientific and Technical Information of China (English)

    LIU Ying-zheng; CHEN Han-ping; KOYAMA Hide S.

    2005-01-01

    Vortex breakdown of the steady axisymmetic rotating flow in a confined cylindrical container with a rotating endwall was numerically and experimentally studied. High-quality precision-controlled turntable facilities were established at Shanghai Jiaotong University and Tokyo Denki University independently. Collaborative investigations of vortex breakdown were carried out using CFD, Laser Doppler Velocimetry (LDV) and streakline visualization, respectively. The characteristics of vortex breakdown were delineated in terms of comparative investigation using numerical and experimental results. SIMPLEC scheme and FMG multigrid was applied to numerical simulation. Numerical simulation was extensively compared with streakline visualization and LDV measurements, showing qualitative and quantitative agreements.

  13. Measurements of electron avalanche formation time in W-band microwave air breakdown

    Science.gov (United States)

    Cook, Alan M.; Hummelt, Jason S.; Shapiro, Michael A.; Temkin, Richard J.

    2011-08-01

    We present measurements of formation times of electron avalanche ionization discharges induced by a focused 110 GHz millimeter-wave beam in atmospheric air. Discharges take place in a free volume of gas, with no nearby surfaces or objects. When the incident field amplitude is near the breakdown threshold for pulsed conditions, measured formation times are ˜0.1-2 μs over the pressure range 5-700 Torr. Combined with electric field breakdown threshold measurements, the formation time data shows the agreement of 110 GHz air breakdown with the similarity laws of gas discharges.

  14. Effect of UV radiation on the growth and breakdown voltage of anodic oxide films on niobium

    International Nuclear Information System (INIS)

    Formation rates of anodic Nb2O5 films grown under galvanostatic conditions decrease in the presence of UV radiation, unlike those grown in the absence of UV radiation. This may be due to the development of a positive space charge near the solution/oxide interface which is responsible for an increase in electronic current in the film during its formation. Value of breakdown voltage also increases in the presence of UV radiations. The effect of current density and resistivity of the solution upon the breakdown voltage, both in the presence and absence of UV radiation, is discussed in terms of Ikonopisov theory of breakdown voltage. (author). 19 refs., 6 figs

  15. Scaling laws for gas breakdown for nanoscale to microscale gaps at atmospheric pressure

    Science.gov (United States)

    Loveless, Amanda M.; Garner, Allen L.

    2016-06-01

    Electronics miniaturization motivates gas breakdown predictions for microscale and smaller gaps, since traditional breakdown theory fails when gap size, d, is smaller than ˜15 μm at atmospheric pressure, patm. We perform a matched asymptotic analysis to derive analytic expressions for breakdown voltage, Vb, at patm for 1 nm ≤ d ≤ 35 μm. We obtain excellent agreement between numerical, analytic, and particle-in-cell simulations for argon, and show Vb decreasing as d → 0, instead of increasing as predicted by Paschen's law. This work provides an analytic framework for determining Vb at atmospheric pressure for various gap distances that may be extended to other gases.

  16. Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor

    Energy Technology Data Exchange (ETDEWEB)

    Saheed, M. Shuaib M.; Muti Mohamed, Norani; Arif Burhanudin, Zainal, E-mail: zainabh@petronas.com.my [Centre of Innovative Nanostructures and Nanodevices, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

    2014-03-24

    Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14 μm. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7 μm gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.

  17. Elemental analysis of cotton by laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Schenk, Emily R.; Almirall, Jose R.

    2010-05-01

    Laser-induced breakdown spectroscopy (LIBS) has been applied to the elemental characterization of unprocessed cotton. This research is important in forensic and fraud detection applications to establish an elemental fingerprint of U.S. cotton by region, which can be used to determine the source of the cotton. To the best of our knowledge, this is the first report of a LIBS method for the elemental analysis of cotton. The experimental setup consists of a Nd:YAG laser that operates at the fundamental wavelength as the LIBS excitation source and an echelle spectrometer equipped with an intensified CCD camera. The relative concentrations of elements Al, Ba, Ca, Cr, Cu, Fe, Mg, and Sr from both nutrients and environmental contributions were determined by LIBS. Principal component analysis was used to visualize the differences between cotton samples based on the elemental composition by region in the U.S. Linear discriminant analysis of the LIBS data resulted in the correct classification of >97% of the cotton samples by U.S. region and >81% correct classification by state of origin.

  18. Single shot depth sensitivity using femtosecond Laser Induced Breakdown Spectroscopy

    International Nuclear Information System (INIS)

    Depth profiling measurement using multiple pulse Laser Induced Breakdown Spectroscopy (LIBS) can be used to determine the characteristics of buried layers. However for femtosecond pulses the emission spectra does not necessarily reflect the average depth composition for the single shot case and instead has much higher sensitivity for the surface layer of the ablation region. We introduce a concept of “depth sensitivity” to characterize this behavior for single shot LIBS depth profiling. Experiments were carried out using 800 nm femtosecond laser pulses irradiating layered targets while monitoring the plasma emission with a spectrometer system. Laser induced plasma formed at the surface layer exhibits a strong LIBS signature while deeper ablated region contributes very little to the emission spectrum. The sensitive depth region, the source of the major part of the emission, is much less than the ablation crater depth and is shown to be of the order of 3 nm in the case of actual crater depths of 100's of nm. A two temperature model has been used to determine the lattice temperature profile versus depth which qualitatively predicts the observed behavior. - Highlights: • Depth dependence of LIBS emission within a single 800 nm femtosecond laser shot. • LIBS emission spectra dominated by only a thin surface layer. • Depth sensitivity, a new concept, is ∼3 nm when actual crater depth ∼100’s of nm. • Qualitative agreement with TTM model of lattice temperature versus depth and time

  19. Laser-induced breakdown spectroscopy expands into industrial applications

    International Nuclear Information System (INIS)

    This paper presents R and D activities in the field of laser-induced breakdown spectroscopy for industrial applications and shows novel LIBS systems running in routine operation for inline process control tasks. Starting with a comparison of the typical characteristics of LIBS with XRF and spark-discharge optical emission spectrometry, the principal structure of LIBS machines embedded for inline process monitoring will be presented. A systematic requirement analysis for LIBS systems following Ishikawa's scheme was worked out. Stability issues are studied for laser sources and Paschen-Runge spectrometers as key components for industrial LIBS systems. Examples of industrial applications range from handheld LIBS systems using a fiber laser source, via a set of LIBS machines for inline process control tasks, such as scrap analysis, coal analysis, liquid slag analysis and finally monitoring of drill dust. - Highlights: • New applications for LIBS realized within the last five years • Systematic requirement analysis for industrial LIBS systems • First long-term studies of key components • Demonstration of LIBS potential for inline chemical analysis

  20. The breakdown of meaning and adolescent problem behavior.

    Science.gov (United States)

    Hazani, Moshe

    2003-01-01

    This paper attempts to account for the upsurge of adolescents' problem behavior in high-income countries in terms of Lifton's paradigm of symbolic immortality. Whilst most of the works dealing with this subject focus on the level of the individual adolescent and his or her surrounding, Lifton shows that societal processes can affect the individual. Drawing upon his approach, it was argued that desymbolization,--the collapse of society's symbols system--produces "divided selves," individuals who harbor an 'aggressor-victim double' in their psyche, wherein an internal conflict between the aggressor and the victim engenders self-destructive impulses. In this study it is hypothesized that problem behaviors are external manifestations of underlying self-destructiveness. Thirty-four Jewish-Israeli adolescents involved in sexual promiscuity, drug abuse, anorexia nervosa, and violence were interviewed. It was found that despite individual and social dissimilarities, and the different problem behaviors, the participants were marked by inner-directed destructiveness as well as a sense of meaninglessness of life and lack of symbolic relationship to what transcends their here-and-now selves. Significantly, violent adolescents whose aggression is other-directed were found to be marked by underlying self-directed aggression as well. If the findings of this study are representative of Israeli society at large or of other affluent societies, then the epidemic proportions of youth problem behavior may indicate that these societies are undergoing desymbolization, a psychocultural breakdown. PMID:12964443

  1. Independent component analysis classification of laser induced breakdown spectroscopy spectra

    Science.gov (United States)

    Forni, Olivier; Maurice, Sylvestre; Gasnault, Olivier; Wiens, Roger C.; Cousin, Agnès; Clegg, Samuel M.; Sirven, Jean-Baptiste; Lasue, Jérémie

    2013-08-01

    The ChemCam instrument on board Mars Science Laboratory (MSL) rover uses the laser-induced breakdown spectroscopy (LIBS) technique to remotely analyze Martian rocks. It retrieves spectra up to a distance of seven meters to quantify and to quantitatively analyze the sampled rocks. Like any field application, on-site measurements by LIBS are altered by diverse matrix effects which induce signal variations that are specific to the nature of the sample. Qualitative aspects remain to be studied, particularly LIBS sample identification to determine which samples are of interest for further analysis by ChemCam and other rover instruments. This can be performed with the help of different chemometric methods that model the spectra variance in order to identify a the rock from its spectrum. In this paper we test independent components analysis (ICA) rock classification by remote LIBS. We show that using measures of distance in ICA space, namely the Manhattan and the Mahalanobis distance, we can efficiently classify spectra of an unknown rock. The Mahalanobis distance gives overall better performances and is easier to manage than the Manhattan distance for which the determination of the cut-off distance is not easy. However these two techniques are complementary and their analytical performances will improve with time during MSL operations as the quantity of available Martian spectra will grow. The analysis accuracy and performances will benefit from a combination of the two approaches.

  2. Mobility, fitness collection, and the breakdown of cooperation.

    Science.gov (United States)

    Gelimson, Anatolij; Cremer, Jonas; Frey, Erwin

    2013-04-01

    The spatial arrangement of individuals is thought to overcome the dilemma of cooperation: When cooperators engage in clusters, they might share the benefit of cooperation while being more protected against noncooperating individuals, who benefit from cooperation but save the cost of cooperation. This is paradigmatically shown by the spatial prisoner's dilemma model. Here, we study this model in one and two spatial dimensions, but explicitly take into account that in biological setups, fitness collection and selection are separated processes occurring mostly on vastly different time scales. This separation is particularly important to understand the impact of mobility on the evolution of cooperation. We find that even small diffusive mobility strongly restricts cooperation since it enables noncooperative individuals to invade cooperative clusters. Thus, in most biological scenarios, where the mobility of competing individuals is an irrefutable fact, the spatial prisoner's dilemma alone cannot explain stable cooperation, but additional mechanisms are necessary for spatial structure to promote the evolution of cooperation. The breakdown of cooperation is analyzed in detail. We confirm the existence of a phase transition, here controlled by mobility and costs, which distinguishes between purely cooperative and noncooperative absorbing states. While in one dimension the model is in the class of the voter model, it belongs to the directed percolation universality class in two dimensions. PMID:23679453

  3. Falling film flow, heat transfer and breakdown on horizontal tubes

    International Nuclear Information System (INIS)

    Knowledge of falling film flow and heat transfer characteristics on horizontal tubes is required in the assessment of certain CANDU reactor accident sequences for those CANDU reactors which use moderator dump as one of the shut-down mechanisms. In these reactors, subsequent cooling of the calandria tubes is provided by falling films produced by sprays. This report describes studies of falling film flow and heat transfer characteristics on horizontal tubes. Analyses using integral methods are given for laminar and turbulent flow, ignoring and accounting for momentum effects in the film. Preliminary experiments on film flow stability on horizontal tubes are described and various mechanisms of film breakdown are examined. The work described in this report shows that in LOCA with indefinitely delayed ECI in the NPD or Douglas Point (at 70 percent power) reactors, the falling films on the calandria tubes will not be disrupted by any of the mechanisms considered, provided that the pressure tubes do not sag onto the calandria tubes. However, should the pressure tubes sag onto the calandria tubes, film disruption will probably occur

  4. RF Breakdown Studies in Tungsten and Copper Structures

    Science.gov (United States)

    Laurent, L.; Adolphsen, C.; Beebe, S.; Döbert, S.; Luhmann, N. C.; Pearson, C.; Rodriguez, J. A.; Scheitrum, G.; Wuensch, W.

    2006-11-01

    This paper reports on experimental results from the SLAC NLC accelerator structure closeout program, and discusses a study that was conducted to improve the smoothness of machined tungsten for use in high gradient structures. At the Next Linear Collider Test Accelerator (NLCTA), an X-band (11.424 GHz) structure was operated at a lower temperature to determine whether this would decrease the low rate of breakdowns that still occur after initial processing. Also, various vacuum venting experiments were performed to determine the impact of air, airborne particulates, and oxidation on the performance of a processed accelerator structure. As part of a more long-range high-gradient structure development program, alternative materials to copper are being explored. The CLIC study group at CERN has conducted several accelerator experiments at 30 GHz with structures that have tungsten and molybdenum iris inserts. SLAC has also tested versions of the CLIC 30 GHz design scaled to 11.424 GHz. The results have prompted a tungsten material study directed at exploring new fabrication processes that would provide a cleaner and smoother tungsten surface topography suitable for high gradient applications. A significantly improved tungsten surface finish resulted from this material study, and a single cell X-band cavity containing noses with such tungsten surfaces will be high power tested soon.

  5. Slag analysis with laser-induced breakdown spectrometry.

    Science.gov (United States)

    Kraushaar, M; Noll, R; Schmitz, H U

    2003-10-01

    Laser-induced breakdown spectrometry (LIBS) has been applied for multi-elemental analysis of slag samples from a steel plant. In order to avoid the time-consuming step of sample preparation, the liquid slag material can be filled in special probes. After cooling of the liquid slag and solidification, the samples can be analyzed with LIBS. Chemical analysis of slag is an essential input parameter used for numerical simulations to control liquid steel processing. The relative variation range of element concentrations in slag samples from steel production can amount to up to 30%. A multivariate calibration model is used to take into account matrix effects caused by these varying concentrations. By optimizing the measuring parameters as well as the calibration models, an agreement between the standard X-ray fluorescence (XRF) analysis and LIBS analysis in terms of the coefficient of determination r2 of 0.99 for the main analytes CaO, SiO2, and Fetot of converter slag samples was achieved. The average repeatability of the LIBS measurement for these elements in terms of the relative standard deviation of the determined concentration is improved to less than 1.0%. With these results, the basis is established for future on-line applications of LIBS in the steel-making industry for slag analysis. PMID:14639759

  6. Analysis Code for High Gradient Dielectric Insulator Surface Breakdown

    Energy Technology Data Exchange (ETDEWEB)

    Ives, Robert Lawrence [Calabazas Creek Research, Inc.; Verboncoeur, John [University of California - Berkeley; Aldan, Manuel [University of California, Berkeley

    2010-05-30

    High voltage (HV) insulators are critical components in high-energy, accelerator and pulsed power systems that drive diverse applications in the national security, nuclear weapons science, defense and industrial arenas. In these systems, the insulator may separate vacuum/non-vacuum regions or conductors with high electrical field gradients. These insulators will often fail at electric fields over an order of magnitude lower than their intrinsic dielectric strength due to flashover at the dielectric interface. Decades of studies have produced a wealth of information on fundamental processes and mechanisms important for flashover initiation, but only for relatively simple insulator configurations in controlled environments. Accelerator and pulsed power system designers are faced with applying the fundamental knowledge to complex, operational devices with escalating HV requirements. Designers are forced to rely on “best practices” and expensive prototype testing, providing boundaries for successful operation. However, the safety margin is difficult to estimate, and system design must be very conservative for situations where testing is not practicable, or replacement of failed parts is disruptive or expensive. The Phase I program demonstrated the feasibility of developing an advanced code for modeling insulator breakdown. Such a code would be of great interest for a number of applications, including high energy physics, microwave source development, fusion sciences, and other research and industrial applications using high voltage devices.

  7. Single machine stochastic JIT scheduling problem subject to machine breakdowns

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In this paper we research the single machine stochastic JIT scheduling problem subject to the machine breakdowns for preemptive-resume and preemptive-repeat.The objective function of the problem is the sum of squared deviations of the job-expected completion times from the due date.For preemptive-resume,we show that the optimal sequence of the SSDE problem is V-shaped with respect to expected processing times.And a dynamic programming algorithm with the pseudopolynomial time complexity is given.We discuss the difference between the SSDE problem and the ESSD problem and show that the optimal solution of the SSDE problem is a good approximate optimal solution of the ESSD problem,and the optimal solution of the SSDE problem is an optimal solution of the ESSD problem under some conditions.For preemptive-repeat,the stochastic JIT scheduling problem has not been solved since the variances of the completion times cannot be computed.We replace the ESSD problem by the SSDE problem.We show that the optimal sequence of the SSDE problem is V-shaped with respect to the expected occupying times.And a dynamic programming algorithm with the pseudopolynomial time complexity is given.A new thought is advanced for the research of the preemptive-repeat stochastic JIT scheduling problem.

  8. Elemental analysis of cotton by laser-induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    Laser-induced breakdown spectroscopy (LIBS) has been applied to the elemental characterization of unprocessed cotton. This research is important in forensic and fraud detection applications to establish an elemental fingerprint of U.S. cotton by region, which can be used to determine the source of the cotton. To the best of our knowledge, this is the first report of a LIBS method for the elemental analysis of cotton. The experimental setup consists of a Nd:YAG laser that operates at the fundamental wavelength as the LIBS excitation source and an echelle spectrometer equipped with an intensified CCD camera. The relative concentrations of elements Al, Ba, Ca, Cr, Cu, Fe, Mg, and Sr from both nutrients and environmental contributions were determined by LIBS. Principal component analysis was used to visualize the differences between cotton samples based on the elemental composition by region in the U.S. Linear discriminant analysis of the LIBS data resulted in the correct classification of >97% of the cotton samples by U.S. region and >81% correct classification by state of origin.

  9. Laser-induced breakdown spectroscopy of tantalum plasma

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Sidra; Bashir, Shazia; Hayat, Asma; Khaleeq-ur-Rahman, M.; Faizan–ul-Haq [Centre for Advanced Studies in Physics, GC University, Lahore (Pakistan)

    2013-07-15

    Laser Induced Breakdown spectroscopy (LIBS) of Tantalum (Ta) plasma has been investigated. For this purpose Q-switched Nd: YAG laser pulses (λ∼ 1064 nm, τ∼ 10 ns) of maximum pulse energy of 100 mJ have been employed as an ablation source. Ta targets were exposed under the ambient environment of various gases of Ar, mixture (CO{sub 2}: N{sub 2}: He), O{sub 2}, N{sub 2}, and He under various filling pressure. The emission spectrum of Ta is observed by using LIBS spectrometer. The emission intensity, excitation temperature, and electron number density of Ta plasma have been evaluated as a function of pressure for various gases. Our experimental results reveal that the optical emission intensity, the electron temperature and density are strongly dependent upon the nature and pressure of ambient environment. The SEM analysis of the ablated Ta target has also been carried out to explore the effect of ambient environment on the laser induced grown structures. The growth of grain like structures in case of molecular gases and cone-formation in case of inert gases is observed. The evaluated plasma parameters by LIBS analysis such as electron temperature and the electron density are well correlated with the surface modification of laser irradiated Ta revealed by SEM analysis.

  10. Altitude Correction for Breakdown Voltages of Long Air-Gaps

    Institute of Scientific and Technical Information of China (English)

    Wang Xuan; Li Yunge; Cao Xiaolong; Su Zhiyi; Liu Ying

    2006-01-01

    The breakdown voltage of long air-gaps in high-voltage transmission systems depends on not only the waveform of the applied voltage, but also the atmospheric conditions. Based on the results of the research project on the minimum air clearance for 800-Kv HVDC substations at high altitudes, and also on the monthly and yearly statistics of the atmospheric data of last ten years and the altitude correction of the atmospheric data of last ten years, the altitude correction of the air-gaps for the 800-Kv DC system under plan, 500-Kv AC system to be built, and 1000-Kv AC system under plan in the Inner Mongolia Plateau and the Yungui Plateau in China were studied with parameter G method. Correction factors for switching and lightning impulses were calculated and then compared with those achieved according to IEC 71. It is shown that IEC 71 is appropriate for damp regions, and correction factors differ between plateau regions in China because of different atmospheric conditions.

  11. Locating initial breakdown pulses using electric field change network

    Science.gov (United States)

    Karunarathne, Sumedhe; Marshall, Thomas C.; Stolzenburg, Maribeth; Karunarathna, Nadeeka; Vickers, Lauren E.; Warner, Tom A.; Orville, Richard E.

    2013-07-01

    Initial breakdown pulses (IBPs) observed in the fast electric field change (E-change) at the beginning of intracloud (IC) and cloud-to-ground (CG) lightning flashes are located using a time-of-arrival technique called Position By Fast Antenna (PBFA) with data from a network of 10 E-change sensors located at Kennedy Space Center. Location errors, estimated using a Monte Carlo method, are usually less than 100 m for horizontal coordinates and several hundreds of meters for altitude, depending on distance to the sensors and altitude of the source. Comparison of PBFA source locations to locations from a VHF lightning mapping system (Lightning Detection and Ranging II (LDAR2)) shows that PBFA locates most of the "classic" IBPs while LDAR2 locates only a few percent of them. As the flash develops during the IB stage, PBFA and LDAR2 obtain similar locations when they detect the same IBPs. The overall vertical motion indicated by the PBFA positions of IBPs was downward with time for CG flashes and upward with time for IC flashes. Location of the fast pulses due to return strokes of CG flashes is also determined using PBFA. Comparison to locations from the Cloud-to-Ground Lightning Surveillance System (CGLSS) shows that PBFA reliably locates ground strokes. These results are verified using ground truth data acquired with a high-speed video camera. After cross calibration with the CGLSS data set, peak currents of return strokes are also determined.

  12. A Laser Breakdown Spectrometer for Environmental Analysis of Metals

    Science.gov (United States)

    Martyshkin, Dmitri; Mirov, Sergey; Lee, Wonwoo; Pitt, Robert

    2000-11-01

    A novel experimental set-up using laser-induced breakdown spectroscopy (LIBS) for environmental analyses of heavy metals is described in this paper. It is based on state-of-the-art spectroscopic equipment, advanced detectors, and laser atomizers: a 0.75 m spectrometer ARC-750, intensified TE-cooled 256x1024 CCD camera, probe with fiber optic guide for signal transportation, and Nd:YAG laser plasma atomizers with two different methods for sample delivery. In the first method the liquid solution containing the atoms to be investigated is drawn into the chamber of the nebulizer. The mixture passes through the nozzle, accompanied by argon gas along with formed aerosol, and enters the plasma plume, which is generated by the laser spark in argon. The second method is based on direct generating of the plasma in the water jet of a continuously circulating sample. LIBS testing of samples containing Al, Cd, Cu, Fe, Pb, Zn, Cr and Eu ions was compared with results using atomic absorption spectrophotometry. Initial indications showed good agreement between these two methods. Detection levels of less than 100 ppb were observed for copper and chromium. The described spectroscopic system exhibits high sensitivity, accumulation of luminescence spectrum in real time; and high dynamic range for concentrations detection from 100 ppb to 1000 ppm.

  13. Laser Induced Breakdown Spectroscopy, advances in resolution and portability

    International Nuclear Information System (INIS)

    Laser Induced Breakdown Spectroscopy (LIBS), can be considered as one of the most dynamic and promising technique in the field of analytical spectroscopy. LIBS has turned into a powerful alternative for a wide front of applications, from the geological exploration to the industrial inspection, including the environmental monitoring, the biomedical analysis, the study of patrimonial works, the safety and defense. The advances in LIBS instrumentation have allowed improving gradually the analysis services and quality, on the basis of a better knowledge of the technology principles. Recently, systems of double pulse have facilitated a better dosing of energy, the improvement of the signal-noise relation and the study of the different process stages. Femtosecond lasers offers the possibility of study in detail the ablation and atomic emission processes. New advances like multi-pulse or multi-wavelength systems -in fact stilling without exploring, must offer new information to advance in this knowledge. Finally, which it does to this technology really attractive, is the aptitude to be employed in field conditions, or for the detection of the elementary composition at long distances. In this presentation there are discussed the designs of portable instrumentation, compact and low cost, which can improve substantially the LIBS possibilities. (Author)

  14. Lead determination in glasses by laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Carmona, N. [Centro Nacional de Investigaciones Metalurgicas, CENIM-CSIC, Gregorio del Amo 8, 28040 Madrid (Spain)], E-mail: ncarmona@cenim.csic.es; Oujja, M.; Gaspard, S. [Instituto de Quimica Fisica Rocasolano, CSIC. Serrano 119, 28006 Madrid (Spain); Garcia-Heras, M. [Centro Nacional de Investigaciones Metalurgicas, CENIM-CSIC, Gregorio del Amo 8, 28040 Madrid (Spain); Instituto de Historia, CSIC. Serrano 13, 28001 Madrid (Spain); Villegas, M.A. [Centro Nacional de Investigaciones Metalurgicas, CENIM-CSIC, Gregorio del Amo 8, 28040 Madrid (Spain); Castillejo, M. [Instituto de Quimica Fisica Rocasolano, CSIC. Serrano 119, 28006 Madrid (Spain)], E-mail: marta.castillejo@iqfr.csic.es

    2007-02-15

    Laser-induced breakdown spectroscopy (LIBS) has been used to determine the lead content of different types of lead silicate glasses commercially designed as sonorous glass (which contain {approx} 10 wt.% PbO); crystal glass (with at least 24 wt.% PbO) and superior crystal glass (with at least 30 wt.% PbO). Seven different types of glass samples were selected, including historic-original, model and commercially available. The selected samples were artificially weathered under neutral, acid and alkaline attack. Analysis by LIBS was carried out in vacuum under excitation at 266 nm and results were compared with those obtained by conventional techniques used for glass characterization. Composition of the bulk glasses was analyzed by XRF (X-ray fluorescence) and the corroded surfaces were characterized by SEM/EDX (scanning electron microscopy/energy dispersive X-ray microanalysis). A linear correlation was obtained between the intensity of selected Pb lines in the LIB spectra and the PbO content. The effect of corrosion could be characterized by comparing successive LIB spectra recorded on the same area; acid attack resulted in a decrease of PbO, CaO and Na{sub 2}O content in the surface with respect to the bulk of the sample, while minor changes in the composition were noticed under alkaline attack. These results show LIBS as a useful technique to classify the different types of lead glasses by their lead content and to determine and asses the degree and type of corrosion.

  15. Single machine stochastic JIT scheduling problem subject to machine breakdowns

    Institute of Scientific and Technical Information of China (English)

    TANG HengYong; ZHAO ChuanLi; CHENG CongDian

    2008-01-01

    In this paper we research the single machine stochastic JIT scheduling problem subject to the machine breakdowns for preemptive-resume and preemptive-repeat. The objective function of the problem is the sum of squared deviations of the job-expected completion times from the due date. For preemptive-resume, we show that the optimal sequence of the SSDE problem is V-shaped with respect to expected processing times. And a dynamic programming algorithm with the pseudopolynomial time complexity is, given. We discuss the difference between the SSDE problem and the ESSD problem and show that the optimal solution of the SSDE problem is a good approximate optimal solution of the ESSD problem, and the optimal solution of the SSDE problem is an optimal solution of the ESSD problem under some conditions. For preemptive-repeat, the stochastic JIT scheduling problem has not been solved since the variances of the completion times cannot be computed. We replace the ESSD problem by the SSDE problem. We show that the optimal sequence of the SSDE problem is V-shaped with respect to the expected occupying times. And a dynamic programming algorithm with the pseudopolynomial time complexity is given. A new thought is advanced for the research of the preemptive-repeat stochastic JIT scheduling problem.

  16. Breakdown and dc discharge in low-pressure water vapour

    Science.gov (United States)

    Sivoš, J.; Škoro, N.; Marić, D.; Malović, G.; Petrović, Z. Lj

    2015-10-01

    In this paper we report studies of basic properties of breakdown, low-current Townsend discharge and high-current discharge regimes in water vapour. Paschen curves and the corresponding distributions of emission intensities at low current were recorded in the range of pd (pressure x electrode gap) from 0.1 to 10 Torrcm covering the region of Paschen minimum. From the experimental profiles we obtained effective ionization coefficient of water vapour for the E/N range 650 Td-7 kTd and fitted the results by using the extended Townsend analytical formula. Using the obtained ionization coefficient, we calculated the effective yield of secondary electrons from the copper cathode. Results of the measurements of Volt-Ampere characteristics in water vapour were presented together with the images of the axial structure of the discharge in a wide range of discharge currents for two pd values. Recorded profiles showed development of the spatial structure of the discharge in different operating regimes. We were able to identify conditions where processes induced by heavy particles, probably fast hydrogen atoms, are dominant in inducing emission from the discharge. Finally, standard scaling laws were tested for low current and glow discharges in water vapour.

  17. Microwave assisted laser-induced breakdown spectroscopy at ambient conditions

    Science.gov (United States)

    Viljanen, Jan; Sun, Zhiwei; Alwahabi, Zeyad T.

    2016-04-01

    Signal enhancements in laser-induced breakdown spectroscopy (LIBS) using external microwave power are demonstrated in ambient air. Pulsed microwave at 2.45 GHz and of 1 millisecond duration was delivered via a simple near field applicator (NFA), with which an external electric field is generated and coupled into laser induced plasma. The external microwave power can significantly increase the signal lifetime from a few microseconds to hundreds of microseconds, resulting in a great enhancement on LIBS signals with the use of a long integration time. The dependence of signal enhancement on laser energy and microwave power is experimentally assessed. With the assistance of microwave source, a significant enhancement of ~ 100 was achieved at relatively low laser energy that is only slightly above the ablation threshold. A limit of detection (LOD) of 8.1 ppm was estimated for copper detection in Cu/Al2O3 solid samples. This LOD corresponds to a 93-fold improvement compared with conventional single-pulse LIBS. Additionally, in the microwave assisted LIBS, the self-reversal effect was greatly reduced, which is beneficial in measuring elements of high concentration. Temporal measurements have been performed and the results revealed the evolution of the emission process in microwave-enhanced LIBS. The optimal position of the NFA related to the ablation point has also been investigated.

  18. Forensic comparative glass analysis by laser-induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    Glass samples of four types commonly encountered in forensic examinations have been analyzed by laser-induced breakdown spectroscopy (LIBS) for the purpose of discriminating between samples originating from different sources. Some of the glass sets were also examined by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Refractive index (RI) measurements were also made on all glass samples and the refractive index data was combined with the LIBS and with the LA-ICP-MS data to enhance discrimination. The glass types examined included float glass taken from front and side automobile windows (examined on the non-float side), automobile headlamp glass, automobile side-mirror glass and brown beverage container glass. The largest overall discrimination was obtained by employing RI data in combination with LA-ICP-MS (98.8% discrimination of 666 pairwise comparisons at 95% confidence), while LIBS in combination with RI provided a somewhat lower discrimination (87.2% discrimination of 1122 pairwise comparisons at 95% confidence). Samples of side-mirror glass were less discriminated by LIBS due to a larger variance in emission intensities, while discrimination of side-mirror glass by LA-ICP-MS remained high

  19. Laser-induced breakdown plasma-based sensors

    Science.gov (United States)

    Griffin, Steven T.

    2010-04-01

    Laser Induced Breakdown Spectroscopy (LIBS) is dependent on the interaction between the initiating Laser sequence, the sampled material and the intermediate plasma states. Pulse shaping and timing have been empirically demonstrated to have significant impact on the signal available for active/passive detection and identification. The transient nature of empirical LIBS work makes data collection for optimization an expensive process. Guidance from effective computer simulation represents an alternative. This computational method for CBRNE sensing applications models the Laser, material and plasma interaction for the purpose of performance prediction and enhancement. This paper emphasizes the aspects of light, plasma, and material interaction relevant to portable sensor development for LIBS. The modeling structure emphasizes energy balances and empirical fit descriptions with limited detailed-balance and finite element approaches where required. Dusty plasma from partially decomposed material sample interaction with pulse dynamics is considered. This heuristic is used to reduce run times and computer loads. Computer simulations and some data for validation are presented. A new University of Memphis HPC/super-computer (~15 TFLOPS) is used to enhance simulation. Results coordinated with related effort at Arkansas State University. Implications for ongoing empirical work are presented with special attention paid to the application of compressive sensing for signal processing, feature extraction, and classification.

  20. Laser-induced breakdown spectroscopy of tantalum plasma

    International Nuclear Information System (INIS)

    Laser Induced Breakdown spectroscopy (LIBS) of Tantalum (Ta) plasma has been investigated. For this purpose Q-switched Nd: YAG laser pulses (λ∼ 1064 nm, τ∼ 10 ns) of maximum pulse energy of 100 mJ have been employed as an ablation source. Ta targets were exposed under the ambient environment of various gases of Ar, mixture (CO2: N2: He), O2, N2, and He under various filling pressure. The emission spectrum of Ta is observed by using LIBS spectrometer. The emission intensity, excitation temperature, and electron number density of Ta plasma have been evaluated as a function of pressure for various gases. Our experimental results reveal that the optical emission intensity, the electron temperature and density are strongly dependent upon the nature and pressure of ambient environment. The SEM analysis of the ablated Ta target has also been carried out to explore the effect of ambient environment on the laser induced grown structures. The growth of grain like structures in case of molecular gases and cone-formation in case of inert gases is observed. The evaluated plasma parameters by LIBS analysis such as electron temperature and the electron density are well correlated with the surface modification of laser irradiated Ta revealed by SEM analysis

  1. Study of Bacterial Samples Using Laser Induced Breakdown Spectroscopy

    Science.gov (United States)

    W, A. Farooq; M, Atif; W, Tawfik; M, S. Alsalhi; Z, A. Alahmed; M, Sarfraz; J, P. Singh

    2014-12-01

    Laser-induced breakdown spectroscopy (LIBS) technique has been applied to investigate two different types of bacteria, Escherichia coli (B1) and Micrococcus luteus (B2) deposited on glass slides using Spectrolaser 7000. LIBS spectra were analyzed using spectrolaser software. LIBS spectrum of glass substrate was compared with bacteria spectra. Ca, Mg, Na, K, P, S, Cl, Fe, Al, Mn, Cu, C, H and CN-band appeared in bacterial samples in air. Two carbon lines at 193.02 nm, 247.88 nm and one hydrogen line at 656.28 nm with intensity ratios of 1.9, 1.83 and 1.53 appeared in bacterial samples B1 and B2 respectively. Carbon and hydrogen are the important components of the bio-samples like bacteria and other cancer cells. Investigation on LIBS spectra of the samples in He and Ar atmospheres is also presented. Ni lines appeared only in B2 sample in Ar atmosphere. From the present experimental results we are able to show that LIBS technique has a potential in the identification and discrimination of different types of bacteria.

  2. Mid-infrared emission from laser-induced breakdown spectroscopy.

    Science.gov (United States)

    Yang, Clayton S-C; Brown, Ei E; Hommerich, Uwe H; Trivedi, Sudhir B; Samuels, Alan C; Snyder, A Peter

    2007-03-01

    Laser-induced breakdown spectroscopy (LIBS) is a powerful analytical technique for detecting and identifying trace elemental contaminants by monitoring the visible atomic emission from small plasmas. However, mid-infrared (MIR), generally referring to the wavelength range between 2.5 to 25 microm, molecular vibrational and rotational emissions generated by a sample during a LIBS event has not been reported. The LIBS investigations reported in the literature largely involve spectral analysis in the ultraviolet-visible-near-infrared (UV-VIS-NIR) region (less than 1 microm) to probe elemental composition and profiles. Measurements were made to probe the MIR emission from a LIBS event between 3 and 5.75 microm. Oxidation of the sputtered carbon atoms and/or carbon-containing fragments from the sample and atmospheric oxygen produced CO(2) and CO vibrational emission features from 4.2 to 4.8 microm. The LIBS MIR emission has the potential to augment the conventional UV-VIS electronic emission information with that in the MIR region. PMID:17389073

  3. Detection of explosives with laser-induced breakdown spectroscopy

    Science.gov (United States)

    Wang, Qian-Qian; Liu, Kai; Zhao, Hua; Ge, Cong-Hui; Huang, Zhi-Wen

    2012-12-01

    Our recent work on the detection of explosives by laser-induced breakdown spectroscopy (LIBS) is reviewed in this paper. We have studied the physical mechanism of laser-induced plasma of an organic explosive, TNT. The LIBS spectra of TNT under single-photon excitation are simulated using MATLAB. The variations of the atomic emission lines intensities of carbon, hydrogen, oxygen, and nitrogen versus the plasma temperature are simulated too. We also investigate the time-resolved LIBS spectra of a common inorganic explosive, black powder, in two kinds of surrounding atmospheres, air and argon, and find that the maximum value of the O atomic emission line SBR of black powder occurs at a gate delay of 596 ns. Another focus of our work is on using chemometic methods such as principle component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) to distinguish the organic explosives from organic materials such as plastics. A PLS-DA model for classification is built. TNT and seven types of plastics are chosen as samples to test the model. The experimental results demonstrate that LIBS coupled with the chemometric techniques has the capacity to discriminate organic explosive from plastics.

  4. Breakdown Localization Studies on the SwissFEL C-band Test Structures

    CERN Document Server

    Klavins, J; Le Pimpec, F; Locans, U; Shipman, N; Stingelin, L; Wohlmuther, M; Zennaro, R

    2013-01-01

    The SwissFEL main LINAC will consist of 104 Cband structures with a nominal accelerating gradient of 28MV/m. First power tests were performed on short constant impedance test-structures composed of eleven double-rounded cups. In order to localize breakdowns, two or three acoustic emission sensors were installed on the test-structures. In order to localize breakdowns we have analysed, in addition to acoustic measurements, the delay and phase of the RF power signals. Parasitic, acoustic noise emitted from the loads of the structure complicated the data interpretation and necessitated appropriate processing of the acoustic signals. The Goals of the experiments were to identify design and manufacturing errors of the structures. The results indicate that breakdowns occur mostly at the input power coupler, as also confirmed by vacuumevents at the same location. The experiments show that the LINAC test-structures fulfil the requirements in breakdown probability. Moreover developing a detection system based on acoust...

  5. Influence of magnetic field on the electrical breakdown characteristics in cylindrical diode

    International Nuclear Information System (INIS)

    The influence of magnetic field on the electrical breakdown properties is investigated by applying a magnetic field along the longitudinal direction in a cylindrical diode for two electrical polarities. Breakdown characteristics in a crossed magnetic field are analyzed with the equivalentreduced-electric-field concept and Townsend criterion. The discharge experiment at reduced pressure is carried out in the moderate magnetic field. Experimental investigation is concentrated on the magnetic dependent behavior of the electrical breakdown in the lower pressure side of Paschen's minimum. It is found that the electrical breakdown characteristics with respect to the magnetic field depend on electrical polarity of the cylindrical diode, which is interpreted by taking the gyromotion of the individual electrons in the diode into accounts under the moderate magnetic field in the lower pressure side of Paschen's minimum

  6. Engineering data management through different breakdown structures in a large-scale project

    CERN Document Server

    Hameri, A P

    2002-01-01

    This document discusses the benefits stemming from managing different project breakdown structures with an engineering data management system. The structures discussed are project breakdown structure (PBS), assembly breakdown structure (ABS), as-built structure and hardware breakdown. Each structure is presented from the quality management point of view and a practical example of each of the four structures is given to illustrate their differences, and to show what kind of engineering information is to be stored in these structures. The main underlying case is that of CERN and its global, over a decade-long Large Hadron Collider project. The approach used for managing the new particle accelerator project is benchmarked against the way large-scale shipbuilding projects are managed. It is concluded that several structures are needed to manage complex system projects, and that linking information between structures plays a crucial role for the overall success of the project. Information technology and the WWW ar...

  7. Fabrication of 4H-SiC Schottky barrier diodes with high breakdown voltages

    CERN Document Server

    Kum, B H; Shin, M W; Park, J D

    1999-01-01

    This paper discusses the fabrication and the breakdown characteristics of 4H-SiC Schottky barrier diodes (SBDs). Optimal processing conditions for the ohmic contacts were extracted using the transmission-line method (TLM) and were applied to the device fabrication. The Ti/4H-SiC SBDs with Si sub x B sub y passivation showed a maximum reverse breakdown voltage of 268 V with a forward current density as high as 70 mA/cm sup 2 at a forward voltage of 2 V. The breakdown of the Pt. 4H-SiC SBDs without any passivation occurred at near 110 V. It is concluded that the breakdown enhancement in the Ti/4H-SiC SBDs can be attributed to the passivation; otherwise, excess surface charge near the edge of the Schottky contact would lead to electric fields of sufficient magnitude to cause field emission.

  8. Effect of magnetic nanoparticles on the lightning impulse breakdown voltage of transformer oil

    Science.gov (United States)

    Ghasemi, J.; Jafarmadar, S.; Nazari, M.

    2015-09-01

    In this study, the lightning impulse breakdown voltage of magnetic nanofluids based on transformer mineral oil for use in power systems was reviewed. Magnetic nanofluids are obtained from dispersion of the magnetic nanoparticles (Fe3 O4) within transformer oil, as the base fluid. The Fe3 O4 nanoparticles, using a coprecipitation method, were synthesized, coated with a surfactant, and dispersed using an ultrasonic processor, within the uninhibited transformer mineral oil NYTRO LIBRA. The lightning impulse breakdown voltage was obtained using sphere-sphere electrodes in an experimental setup for nano-oil, in volume concentration of 0.1-0.6%. Results indicate improved lightning impulse breakdown voltage under optimal conditions. Increase in the lightning impulse breakdown voltage of the nano-oil is mainly due to the dielectric and magnetic properties of Fe3 O4 nanoparticles, acting as free electrons snapper, and reduce the rate of free electrons production in the ionization process.

  9. The effect of polymer type on electric breakdown strength on a nanosecond time scale

    International Nuclear Information System (INIS)

    Based on the concepts of fast polarization, effective electric field and electron impact ionization criterion, the effect of polymer type on electric breakdown strength (EBD) on a nanosecond time scale is investigated, and a formula that qualitatively characterizes the relation between the electric breakdown strength and the polymer type is derived. According to this formula, it is found that the electric breakdown strength decreases with an increase in the effective relative dielectric constants of the polymers. By calculating the effective relative dielectric constants for different types of polymers, the theoretical relation for the electric breakdown strengths of common polymers is predicted. To verify the prediction, the polymers of PE (polyethylene), PTFE (polytetrafluoroethelene), PMMA (organic glass) and Nylon are tested with a nanosecond-pulse generator. The experimental result shows EBD (PTFE) > EBD (PMMA) > EBD (Nylon) > EBD (PE). This result is consistent with the theoretical prediction. (atomic and molecular physics)

  10. A model based DC analysis of SiPM breakdown voltages

    CERN Document Server

    Nagy, Ferenc; Kalinka, Gabor; Molnar, Jozsef

    2016-01-01

    A new method to determine the breakdown voltage of SiPMs is presented. It is backed up by a DC model which describes the breakdown phenomenon by distinct avalanche turn-on ($V_{01}$) and turn off ($V_{10}$) voltages. It is shown that $V_{01}$ is related to the 'breakdown voltage' that previous DC methods derive from simple reverse current-voltage measurements, while $V_{10}$ is the 'real' breakdown voltage commonly obtained from complex gain-voltage measurements. The proposed method reveals how the microcell population distributes around $V_{01}$ and $V_{10}$. It is found that if this distribution is assumed to be normal, then both voltages and even their standard deviation can readily be extracted from current-voltage curves. Measurements are in good agreement with the theoretical model.

  11. Studying the Dynamics of Breakdown of Thin Horizontal Liquid Layers with Local Heating

    Directory of Open Access Journals (Sweden)

    Spesivtsev Serafim

    2016-01-01

    Full Text Available Experimental study of liquid layers breakdown when heated locally from the substrate side was made. Water and ethanol were used as working liquids with a layer thickness of 300 μm. Basic steps of the breakdown process were found and mean velocities of the dry spot formation were determined; the values are 0.06 mm/sec for ethanol and 5.15 mm/sec for water. The formation of residual layer over the hot-spot before the breakdown has been found for both liquids. The creation of a droplet cluster near the heating region is observed when using water as a working fluid. It was shown that evaporation is one of the general factors influencing the process of layer breakdown and dry spot formation as well as thermocapillary effect.

  12. High voltage breakdown capabilities of high temperature insulation coatings for HTS and LTS conductors

    International Nuclear Information System (INIS)

    High temperature ZrO2 based coatings were deposited on Ag and Ag/AgMg sheathed Bi-2212 tapes from solutions derived from alkoxide-based precursors using a reel-to-reel, continuous sol-gel technique. The insulation coatings were annealed at 850 deg. C for 20 hours under O2 flow. The surface morphology and structure of coatings were characterized by SEM and XRD. High voltage breakdown of insulation on tapes was measured by a standard high voltage breakdown power supply. It has been found that high voltage breakdown values of these insulations strongly depend on number of dipping, thickness, coating type, annealing conditions, and dopant content in ZrO2. 20% Y2O3-ZrO2 coatings showed the best high voltage breakdown value, 2.05 kV at 1.5 mA

  13. Can surface cracks and unipolar arcs explain breakdown and gradient limits?

    CERN Document Server

    Norem, Jim

    2012-01-01

    We argue that the physics of unipolar arcs and surface cracks can help understand rf breakdown, and vacuum arc data. We outline a model of the basic mechanisms involved in breakdown and explore how the physics of unipolar arcs and cracks can simplify the picture of breakdown and gradient limits in accelerators, tokamaks as well as laser ablation, micrometeorites and other applications. Cracks are commonly seen in SEM images of arc damage and they are produced as the liquid metal cools, they produce the required field enhancements to explain field emission data data and can produce fractures that would trigger breakdown events. Unipolar arcs can produce currents sufficient to short out rf structures, should cause the sort of damage seen in SEM images, should be unstable and possibly self-quenching as seen in optical fluctuations and surface damage.

  14. Quantitative measurement of electron number in nanosecond and picosecond laser-induced air breakdown

    Science.gov (United States)

    Wu, Yue; Sawyer, Jordan C.; Su, Liu; Zhang, Zhili

    2016-05-01

    Here we present quantitative measurements of total electron numbers in laser-induced air breakdown at pressures ranging from atmospheric to 40 barg by 10 ns and 100 ps laser pulses. A quantifiable definition for the laser-induced breakdown threshold is identified by a sharp increase in the measurable total electron numbers via dielectric-calibrated coherent microwave scattering. For the 10 ns laser pulse, the threshold of laser-induced breakdown in atmospheric air is defined as the total electron number of ˜106. This breakdown threshold decreases with an increase of pressure and laser photon energy (shorter wavelength), which is consistent with the theory of initial multiphoton ionization and subsequent avalanche processes. For the 100 ps laser pulse cases, a clear threshold is not present and only marginal pressure effects can be observed, which is due to the short pulse duration leading to stronger multiphoton ionization and minimal collisional avalanche ionization.

  15. The Gate-Oxide Breakdown Effect Coupled by Channel Hot-Carrier-Effect in SOI MOSFET's

    Institute of Scientific and Technical Information of China (English)

    HAO Yue; ZHU Jiangang; REN Hongxia; ZHANG Weidong

    2001-01-01

    Based on SIMOS SOI devices, the gate-oxide breakdown effect coupled by channel hot carriers is studied in this paper. It is found that,in n-channel devices, the gate-oxide breakdown is at tributed to the fixed defect in SiO2 crystal lattice structure induced by high-energy hole injection into gate oxide. And the trapping of electron negative charge in gate oxide also accelerates the breakdown.While in PMOS devices, both local electric field in oxide enhancement caused by trapped electrons ,and the electric field on interface increasing induced by trapped holes and the generation of permanent damage in crystal lattice, can lead to gate oxide breakdown directly. The studies also show that the behavior after oxide layer broken down in NMOS and PMOS is different.

  16. The inception of pulsed discharges in air: simulations in background fields above and below breakdown

    CERN Document Server

    Sun, Anbang; Ebert, Ute

    2014-01-01

    We investigate discharge inception in air, in uniform background electric fields above and below the breakdown threshold. We perform 3D particle simulations that include a natural level of background ionization in the form of positive and O$_{2}^-$ ions. When the electric field rises above the breakdown and the detachment threshold, which are similar in air, electrons can detach from O$_{2}^-$ and start ionization avalanches. These avalanches together create one large discharge, in contrast to the `double-headed' streamers found in many fluid simulations. On the other hand, in background fields below breakdown, something must enhance the field sufficiently for a streamer to form. We use a strongly ionized seed of electrons and positive ions for this, with which we observe the growth of positive streamers. Negative streamers were not observed. Below breakdown, the inclusion of electron detachment does not change the results much, and we observe similar discharge development as in fluid simulations.

  17. Subnanosecond processes in the stage of breakdown formation in gas at a high pressure

    Science.gov (United States)

    Korolev, Yu. D.; Bykov, N. M.; Ivanov, S. N.

    2008-12-01

    Results are presented from experimental studies of the prebreakdown stage of a discharge in nitrogen at pressures of a few tens of atmospheres, gap voltages higher than 140 kV, and a voltage rise time of about 1 ns. Breakdown occurs at the front of the voltage pulse; i.e., the time of breakdown formation is shorter than the front duration. It is shown that, in gaps with a nonuniform electric field, the breakdown formation time is mainly determined by the time of avalanche development to the critical number of charge carriers. The subsequent stages of breakdown (the development of the ionization wave and the buildup of the conductivity in the weakly conducting channel bridging the gap) turn out to be shorter than this time or comparable to it.

  18. Drought, Mutualism Breakdown, and Landscape-Scale Degradation of Seagrass Beds

    NARCIS (Netherlands)

    de Fouw, J.; Govers, L.; van de Koppel, J.; van Belzen, J.; Dorigo, W.; Sidi Cheikh, M.A.; Christianen, M.J.A.; van der Reijden, K.J.; van der Geest, M.; Piersma, T,; Smolders, A.J.P.; Olff, H.; Lamers, L.P.M.; van Gils, J.A.; van der Heide, T.

    2016-01-01

    In many marine ecosystems, biodiversity criticallydepends on foundation species such as corals andseagrasses that engage in mutualistic interactions[1–3]. Concerns grow that environmental disruptionof marine mutualisms exacerbates ecosystem degradation,with breakdown of the obligate coral mutualism(

  19. Electrical breakdown and electronic current of niobium-niobium oxide-electrolyte systems

    International Nuclear Information System (INIS)

    Breakdown voltages and electronic current data (at constant voltage) for anodic niobium oxide films in contact with mixed solutions of aqueous electrolytes + diethylene glycol of varying concentrations and compositions at 308 K have been obtained. Breakdown voltage as well as electronic current have been found to depend on electrolyte concentration, composition and resistivity. The effects of electrolyte concentration, composition and resistivity on breakdown voltage have been discussed in terms of Ikonopisov electron avalanche model and the theory of Di Quarto. The values of parameters for impact ionization co-efficient (α) and primary electronic current (j0) have been evaluated. The major factor contributing to the decrease in breakdown voltage with increasing electrolyte concentration is the increasing primary electronic current, j0. (author). 10 refs., 5 figs., 2 tabs

  20. Improving sensitivity of laser-induced breakdown spectroscopy using laser plasmas interaction

    Science.gov (United States)

    Il'in, Alexey A.; Golik, Sergey S.; Nagorny, Ivan G.; Bulanov, Alexey V.

    2006-11-01

    Laser plasmas interaction and spectral characteristics of plasma were investigated at a laser breakdown in a normal atmosphere with the purpose of improving laser-induced breakdown spectroscopy sensitivity. Colliding plasmas interaction was investigated depending on mechanism of absorption wave of laser radiation and distance between foci. Laser supported detonation wave, breakdown wave and fast wave of ionization are absorption wave observed in experiment. It was shown that seed electrons for cascade breakdown in front of fast wave of ionization is occurred due to oxygen molecules photoionization. Molecular emission and collapse of intensity of plasma continuum during the initial moments of laser plasma expansion were registered. The line/continuum ratio was essentially increased in case of laser plasmas interaction. Thus laser plasmas interaction improves sensitivity of LIBS.

  1. Reversible post-breakdown conduction in aluminum oxide-polymer capacitors

    OpenAIRE

    CHEN, Qian; Gomes, HL; Rocha, PRF; De Leeuw,; Meskers, SCJ Stefan

    2013-01-01

    Aluminum/Al2O3/polymer/metal capacitors submitted to a low-power constant current stress undergo dielectric breakdown. The post-breakdown conduction is metastable, and over time the capacitors recover their original insulating properties. The decay of the conduction with time follows a power law (1/t) α . The magnitude of the exponent α can be raised by application of an electric field and lowered to practically zero by optical excitation of the polyspirofluorene polymer. The metastable condu...

  2. Blocking the Metabolism of Starch Breakdown Products in Arabidopsis Leaves Triggers Chloroplast Degradation

    OpenAIRE

    Stettler, Michaela; Eicke, Simona; Mettler, Tabea; Messerli, Gaëlle; Hörtensteiner, Stefan; Zeeman, Samuel C.

    2009-01-01

    In most plants, a large fraction of photo-assimilated carbon is stored in the chloroplasts during the day as starch and remobilized during the subsequent night to support metabolism. Mutations blocking either starch synthesis or starch breakdown in Arabidopsis thaliana reduce plant growth. Maltose is the major product of starch breakdown exported from the chloroplast at night. The maltose excess 1 mutant (mex1), which lacks the chloroplast envelope maltose transporter, accumulates high levels...

  3. Effect of Induced Charge on the Passivity and Passivity Breakdown of 304LN Stainless Steels

    OpenAIRE

    Gargi Roy Chowdhury; Mitra, P.K.

    2011-01-01

    Passivity breakdown of stainless steel by pitting in chloride environment is believed to occur at point at zero charge (pzc). So, the nature and quantity of charge on the surface plays a very important role on the breakdown of passivity, as chloride ion adsorption depends on that. In this work a DC potential was maintained between aluminium and graphite electrodes, and the aluminium electrode, in turn, was kept in the vicinity of the working electrode in the potentiostatic circuit. Both posit...

  4. Modification of Pectin and Hemicellulose Polysaccharides in Relation to Aril Breakdown of Harvested Longan Fruit

    OpenAIRE

    Duoduo Wang; Haiyan Zhang; Fuwang Wu; Taotao Li; Yuxiang Liang; Xuewu Duan

    2013-01-01

    To investigate the modification of cell wall polysaccharides in relation to aril breakdown in harvested longan fruit, three pectin fractions (WSP, water soluble pectin; CSP, CDTA-soluble pectin; ASP, alkali soluble pectin) and one hemicellulose fraction (4 M KOH-SHC, 4 M KOH-soluble hemicellulose) were extracted, and their contents, monosaccharide compositions and molecular weights were evaluated. As aril breakdown intensified, CSP content increased while ASP and 4 M KOH-SHC contents decreas...

  5. Transport parameters and breakdown voltage characteristics of the dry air and its constituents

    International Nuclear Information System (INIS)

    This paper contains measured breakdown voltage curves and calculated transport parameters for the dry air and gases included in the air composition. The breakdown voltage curves exhibit U-shaped form for the interelectrode separation of 100 μm and departure from the standard Paschen law for a few micrometers gap sizes. The results of calculations provide an insight into similarities and differences between the transport parameters for individual gases and the gas mixture.

  6. Electrical polarization of nuclear spins in a breakdown regime of quantum Hall effect

    OpenAIRE

    Kawamura, M.; Takahashi, H; Sugihara, K; Masubuchi, S.; Hamaya, K.; Machida, T.

    2006-01-01

    We have developed a method for electrical polarization of nuclear spins in quantum Hall systems. In a breakdown regime of odd-integer quantum Hall effect (QHE), excitation of electrons to the upper Landau subband with opposite spin polarity dynamically polarizes nuclear spins through the hyperfine interaction. The polarized nuclear spins in turn accelerate the QHE breakdown, leading to hysteretic voltage-current characteristics of the quantum Hall conductor.

  7. Dynamic nuclear polarization and Knight shift measurements in a breakdown regime of integer quantum Hall effect

    OpenAIRE

    Kawamura, M.; Takahashi, H; Masubuchi, S.; Hashimoto, Y.; Katsumoto, S.; Hamaya, K.; Machida, T.

    2007-01-01

    Nuclear spins are polarized electrically in a breakdown regime of an odd-integer quantum Hall effect (QHE). Electron excitation to the upper Landau subband with the opposite spin polarity flips nuclear spins through the hyperfine interaction. The polarized nuclear spins reduce the spin-splitting energy and accelerate the QHE breakdown. The Knight shift of the nuclear spins is also measured by tuning electron density during the irradiation of radio-frequency magnetic fields.

  8. Interaction Of CO2 Laser Nanosecond Pulse Train With The Metallic Targets In Optical Breakdown Regime

    Science.gov (United States)

    Apollonov, V. V.; Firsov, K. N.; Konov, V. I.; Nikitin, P. I.; Prokhorov, A. M.; Silenok, A. S.; Sorochenko, V. R.

    1986-11-01

    In the present paper the electric field and currents in the air-breakdown plasma, produced by the train of nanosecond pulses of TEA-002 - regenerative amplifier near the un-charged targets are studied. The breakdown thresholds and the efficiency of plasma-target heat transmission are also measured. The results of numerical calculations made for increasing of the pulse train contrast with respect to the background in a regenerative amplifier are advanced.

  9. A Model for the Voltage Steps in the Breakdown of the Integer Quantum Hall Effect

    OpenAIRE

    Martin, A. M.; Benedict, K.A.; Sheard, F. W.; Eaves, L.

    2002-01-01

    In samples used to maintain the US resistance standard the breakdown of the dissipationless integer quantum Hall effect occurs as a series of dissipative voltage steps. A mechanism for this type of breakdown is proposed, based on the generation of magneto-excitons when the quantum Hall fluid flows past an ionised impurity above a critical velocity. The calculated generation rate gives a voltage step height in good agreement with measurements on both electron and hole gases. We also compare th...

  10. A quasi-analytical breakdown voltage model in four-layer punch-through TVS devices

    Science.gov (United States)

    Urresti, Jesus; Hidalgo, Salvador; Flores, David; Roig, Jaume; Rebollo, José; Mazarredo, Imanol

    2005-08-01

    A quasi-analytical model addressed to predict the breakdown voltage in four-layer transient voltage suppressor (TVS) diodes based on the punch-through effect is reported in this paper. For breakdown voltage in excess of 1 V, a closed form expression is derived. In addition, the three-layer TVS diode can also be described with the developed model. Finally, results obtained from the model are in good agreement with simulation and experimental data.

  11. Laser-induzierte Breakdown Detektion (LIBD): Quantifizierung der Kolloidbildung vierwertiger Actiniden und Homologen.

    OpenAIRE

    Bitea, Claudia

    2004-01-01

    Zusammenfassung Das Ziel der Arbeit ist die Anwendung der Laser-induzierten Breakdown Detektion (LIBD) zur Untersuchung von Kolloidbildungsprozessen vierwertiger Actiniden und Homologen. LIBD ist eine hochempfindliche Detektionsmethode zur Bestimmung der Größe und Anzahldichte aquatischer Kolloide. Die Methode beruht auf dem dielektrischen Zusammenbruch („breakdown“) in Materie durch die Absorption eines Laserstrahles. Im Fokus des Laserstrahles wird so eine hohe Ener...

  12. Effects of load voltage on voltage breakdown modes of electrical exploding aluminum wires in air

    International Nuclear Information System (INIS)

    The effects of the load voltage on the breakdown modes are investigated in exploding aluminum wires driven by a 1 kA, 0.1 kA/ns pulsed current in air. From laser probing images taken by laser shadowgraphy, schlieren imaging, and interferometry, the position of the shockwave front, the plasma channel, and the wire core edge of the exploding product can be determined. The breakdown mode makes a transition from the internal mode, which involves breakdown inside the wire core, to the shunting mode, which involves breakdown in the compressed air, with decreasing charging voltage. The breakdown electrical field for a gaseous aluminum wire core of nearly solid density is estimated to be more than 20 kV/cm, while the value for gaseous aluminum of approximately 0.2% solid density decreases to 15–20 kV/cm. The breakdown field in shunting mode is less than 20 kV/cm and is strongly affected by the vaporized aluminum, the desorbed gas, and the electrons emitted from the wire core during the current pause. Ohmic heating during voltage collapses will induce further energy deposition in the current channel and thus will result in different expansion speeds for both the wire core and the shockwave front in the different modes

  13. Analytical model of the breakdown mechanism in a two-phase mixture

    International Nuclear Information System (INIS)

    A two-phase mixture (TPM) is a mixture of gas and macroparticles of high concentration. It is of interest in many different areas, such as in macroparticle-contaminated insulated systems, gas-liquid discharges, dusty plasmas and processing plasmas. Based on Townsend's theory, a physical model in analytical form for the breakdown mechanism in TPM is presented. In this model, two factors that influence the electron avalanche propagation are considered: macroparticles distorting the electric field and capture of the electrons. According to this breakdown mechanism and the dipole-enhanced model for calculating the maximum local field strength in TPM, the modified Paschen' law for TPM is presented to calculate the breakdown voltage. When the number of series of macroparticles (m) between two plate electrodes is very small, such as when m = 1, the breakdown voltage of the TPM is always lower than that of gas. With an increase in m or a decrease in the radius of macroparticles, the breakdown voltage tends to increase gradually for the same volume fraction of macroparticles. When m >> 1, the breakdown voltage of TPM may be lower or higher than that of gas, depending on the ratio of the number of saturation electrons captured by a macroparticle to the cell primary electrons generated at the cathode. Some other relevant factors, such as the volume fraction of macroparticles, the dielectric mismatch, the charging rate and the product of gas pressure and the gas length, are also discussed

  14. Effects of load voltage on voltage breakdown modes of electrical exploding aluminum wires in air

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jian; Li, Xingwen, E-mail: xwli@mail.xjtu.edu.cn; Yang, Zefeng; Wang, Kun; Chao, Youchuang; Shi, Zongqian; Jia, Shenli; Qiu, Aici [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Xi' an 710049 (China)

    2015-06-15

    The effects of the load voltage on the breakdown modes are investigated in exploding aluminum wires driven by a 1 kA, 0.1 kA/ns pulsed current in air. From laser probing images taken by laser shadowgraphy, schlieren imaging, and interferometry, the position of the shockwave front, the plasma channel, and the wire core edge of the exploding product can be determined. The breakdown mode makes a transition from the internal mode, which involves breakdown inside the wire core, to the shunting mode, which involves breakdown in the compressed air, with decreasing charging voltage. The breakdown electrical field for a gaseous aluminum wire core of nearly solid density is estimated to be more than 20 kV/cm, while the value for gaseous aluminum of approximately 0.2% solid density decreases to 15–20 kV/cm. The breakdown field in shunting mode is less than 20 kV/cm and is strongly affected by the vaporized aluminum, the desorbed gas, and the electrons emitted from the wire core during the current pause. Ohmic heating during voltage collapses will induce further energy deposition in the current channel and thus will result in different expansion speeds for both the wire core and the shockwave front in the different modes.

  15. Multivariate Analysis of Laser-Induced Breakdown Spectroscopy for Discrimination between Explosives and Plastics

    Institute of Scientific and Technical Information of China (English)

    WANG Qian-Qian; LIU Kai; ZHAO Hua

    2012-01-01

    A method to distinguish explosives from plastics using laser-induced breakdown spectroscopy is discussed. A model for classification with cross-validation theory is built based on the partial least-square discriminant analysis method. Seven types of plastics and one explosive are used as samples to test the model. The experimental results demonstrate that laser-induced breakdown spectroscopy has the capacity to discriminate explosives from plastics combined with chemometrics methods. The results could be useful for prospective research of laser-induced breakdown spectroscopy on the differentiation of explosives and other materials.%A method to distinguish explosives from plastics using laser-induced breakdown spectroscopy is discussed.A model for classification with cross-validation theory is built based on the partial least-square discriminant analysis method.Seven types of plastics and one explosive are used as samples to test the model.The experimental results demonstrate that laser-induced breakdown spectroscopy has the capacity to discriminate explosives from plastics combined with chemometrics methods.The results could be useful for prospective research of laser-induced breakdown spectroscopy on the differentiation of explosives and other materials.

  16. Modification of Pectin and Hemicellulose Polysaccharides in Relation to Aril Breakdown of Harvested Longan Fruit

    Directory of Open Access Journals (Sweden)

    Duoduo Wang

    2013-11-01

    Full Text Available To investigate the modification of cell wall polysaccharides in relation to aril breakdown in harvested longan fruit, three pectin fractions (WSP, water soluble pectin; CSP, CDTA-soluble pectin; ASP, alkali soluble pectin and one hemicellulose fraction (4 M KOH-SHC, 4 M KOH-soluble hemicellulose were extracted, and their contents, monosaccharide compositions and molecular weights were evaluated. As aril breakdown intensified, CSP content increased while ASP and 4 M KOH-SHC contents decreased, suggesting the solubilization and conversion of cell wall components. Furthermore, the molar percentage of arabinose (Ara, as the main component of the side-chains, decreased largely in CSP and ASP while that of rhamnose (Rha, as branch point for the attachment of neutral sugar side chains, increased during aril breakdown. Analysis of (Ara + Gal/Rha ratio showed that the depolymerization of CSP and ASP happened predominantly in side-chains formed of Ara residues. For 4 M KOH-SHC, more backbones were depolymerized during aril breakdown. Moreover, it was found that the molecular weights of CSP, ASP and 4 M KOH-SHC polysaccharides tended to decrease as aril breakdown intensified. These results suggest that both enhanced depolymerization and structural modifications of polysaccharides in the CSP, ASP and 4 M KOH-SHC fractions might be responsible for aril breakdown of harvested longan fruit.

  17. Breakdown in ZnO Varistors by High Power Electrical Pulses; TOPICAL

    International Nuclear Information System (INIS)

    This report documents an investigation of irreversible electrical breakdown in ZnO varistors due to short pulses of high electric field and current density. For those varistors that suffer breakdown, there is a monotonic, pulse-by-pulse degradation in the switching electric field. The electrical and structural characteristics of varistors during and after breakdown are described qualitatively and quantitatively. Once breakdown is nucleated, the degradation typically follows a well-defined relationship between the number of post-initiation pulses and the degraded switching voltage. In some cases the degraded varistor has a remnant 20(micro)m diameter hollow track showing strong evidence of once-molten ZnO. A model is developed for both electrical and thermal effects during high energy pulsing. The breakdown is assumed to start at one electrode and advance towards the other electrode as a thin filament of conductive material that grows incrementally with each successive pulse. The model is partially validated by experiments in which the varistor rod is cut at several different lengths from the electrode. Invariably one section of the cut varistor has a switching field that is not degraded while the other section(s) are heavily degraded. Based on the experiments and models of behavior during breakdown, some speculations about the nature of the nucleating mechanism are offered in the last section

  18. Effect of laser pulse repetition frequency on the optical breakdown threshold of quartz glass

    International Nuclear Information System (INIS)

    The thresholds of optical breakdown in the volume of quartz glass were measured in relation to the number of pulses under irradiation by ultrashort laser pulses with different pulse repetition frequencies (1 – 400 kHz). Increasing this frequency from 10 to 400 kHz was found to substantially lower the breakdown threshold for 500-fs long pulses (at a wavelength of 1030 nm) and to lower to a smaller degree for 5-ps long pulses (515 nm). A strong frequency dependence of the breakdown threshold is observed under the same conditions as a manifold decrease of the breakdown threshold with increase in the number of pulses in a pulse train. The dependence of the optical breakdown on the number of pulses is attributable to the accumulation of point defects under multiple subthreshold irradiation, which affects the mechanism of collisional ionisation. In this case, the frequency dependence of the breakdown threshold of quartz glass is determined by the engagement of shortlived defects in the ionisation mechanism. (interaction of laser radiation with matter)

  19. Biotic and abiotic variables influencing plant litter breakdown in streams: a global study.

    Science.gov (United States)

    Boyero, Luz; Pearson, Richard G; Hui, Cang; Gessner, Mark O; Pérez, Javier; Alexandrou, Markos A; Graça, Manuel A S; Cardinale, Bradley J; Albariño, Ricardo J; Arunachalam, Muthukumarasamy; Barmuta, Leon A; Boulton, Andrew J; Bruder, Andreas; Callisto, Marcos; Chauvet, Eric; Death, Russell G; Dudgeon, David; Encalada, Andrea C; Ferreira, Verónica; Figueroa, Ricardo; Flecker, Alexander S; Gonçalves, José F; Helson, Julie; Iwata, Tomoya; Jinggut, Tajang; Mathooko, Jude; Mathuriau, Catherine; M'Erimba, Charles; Moretti, Marcelo S; Pringle, Catherine M; Ramírez, Alonso; Ratnarajah, Lavenia; Rincon, José; Yule, Catherine M

    2016-04-27

    Plant litter breakdown is a key ecological process in terrestrial and freshwater ecosystems. Streams and rivers, in particular, contribute substantially to global carbon fluxes. However, there is little information available on the relative roles of different drivers of plant litter breakdown in fresh waters, particularly at large scales. We present a global-scale study of litter breakdown in streams to compare the roles of biotic, climatic and other environmental factors on breakdown rates. We conducted an experiment in 24 streams encompassing latitudes from 47.8° N to 42.8° S, using litter mixtures of local species differing in quality and phylogenetic diversity (PD), and alder (Alnus glutinosa) to control for variation in litter traits. Our models revealed that breakdown of alder was driven by climate, with some influence of pH, whereas variation in breakdown of litter mixtures was explained mainly by litter quality and PD. Effects of litter quality and PD and stream pH were more positive at higher temperatures, indicating that different mechanisms may operate at different latitudes. These results reflect global variability caused by multiple factors, but unexplained variance points to the need for expanded global-scale comparisons. PMID:27122551

  20. Discriminating crude oil grades using laser-induced breakdown spectroscopy

    Science.gov (United States)

    El-Hussein, A.; Marzouk, A.; Harith, M. A.

    2015-11-01

    The analysis of crude oil using laser-based analytical techniques such as laser-induced breakdown spectroscopy (LIBS) has become of great interest to various specialists in different fields such as geology, petro-chemistry and environmental science. In this work, a detailed study is presented wherein the implementation of an efficient and simple LIBS technique to identify the elemental constituents of crude oil and to distinguish between different grades of petroleum crude oil is discussed. Laser-induced plasma (LIP) technique has been used in this work for direct measurements of atomic, ionic and molecular species in dry crude oil samples with API gravities ranging between 18 and 36. The technique was implemented using the first harmonic of a pulsed Nd-YAG laser source. Atomic and molecular emission bands were observed, consisting of characteristic spectral lines of atoms and diatomic molecular bands, namely from C, H, Si, Na, Ca, Mg, AL, Fe, Ti, Mo, C2 and CN. The intensities of high-resolution spectral lines for some atoms and molecules of elements such as Ca, Na, Fe, Mo, C2 and CN were evaluated at different wavelengths along the obtained spectra. The molecular bands and the elemental spectral lines were used to assess the possibility of adopting the LIBS technique in differentiating between crude oil samples with different American Petroleum Institute (API) gravity values. The results indicate the presence of a distinct correlation between the API gravity values of the various oil samples and the spectral line intensities of the elements and some molecular radical constituents. In addition, the possibility of identifying the API gravity values of unknown oil samples is also indicated.

  1. Application of Laser Induced Breakdown Spectroscopy under Polar Conditions

    Science.gov (United States)

    Clausen, J. L.; Hark, R.; Bol'shakov, A.; Plumer, J.

    2015-12-01

    Over the past decade our research team has evaluated the use of commercial-off-the-shelf laser-induced breakdown spectroscopy (LIBS) for chemical analysis of snow and ice samples under polar conditions. One avenue of research explored LIBS suitability as a detector of paleo-climate proxy indicators (Ca, K, Mg, and Na) in ice as it relates to atmospheric circulation. LIBS results revealed detection of peaks for C and N, consistent with the presence of organic material, as well as major ions (Ca, K, Mg, and Na) and trace metals (Al, Cu, Fe, Mn, Ti). The detection of Ca, K, Mg, and Na confirmed that LIBS has sufficient sensitivity to be used as a tool for characterization of paleo-climate proxy indicators in ice-core samples. Techniques were developed for direct analysis of ice as well as indirect measurements of ice via melting and filtering. Pitfalls and issues of direct ice analysis using several cooling techniques to maintain ice integrity will be discussed. In addition, a new technique, laser ablation molecular isotopic spectroscopy (LAMIS) was applied to detection of hydrogen and oxygen isotopes in ice as isotopic analysis of ice is the main tool in paleoclimatology and glaciology studies. Our results demonstrated that spectra of hydroxyl isotopologues 16OH, 18OH, and 16OD can be recorded with a compact spectrograph to determine hydrogen and oxygen isotopes simultaneously. Quantitative isotopic calibration for ice analysis can be accomplished using multivariate chemometric regression as previously realized for water vapor. Analysis with LIBS and LAMIS required no special sample preparation and was about ten times faster than analysis using ICP-MS. Combination of the two techniques in one portable instrument for in-field analysis appears possible and would eliminate the logistical and cost issues associated with ice core management.

  2. Independent component analysis classification of laser induced breakdown spectroscopy spectra

    International Nuclear Information System (INIS)

    The ChemCam instrument on board Mars Science Laboratory (MSL) rover uses the laser-induced breakdown spectroscopy (LIBS) technique to remotely analyze Martian rocks. It retrieves spectra up to a distance of seven meters to quantify and to quantitatively analyze the sampled rocks. Like any field application, on-site measurements by LIBS are altered by diverse matrix effects which induce signal variations that are specific to the nature of the sample. Qualitative aspects remain to be studied, particularly LIBS sample identification to determine which samples are of interest for further analysis by ChemCam and other rover instruments. This can be performed with the help of different chemometric methods that model the spectra variance in order to identify a the rock from its spectrum. In this paper we test independent components analysis (ICA) rock classification by remote LIBS. We show that using measures of distance in ICA space, namely the Manhattan and the Mahalanobis distance, we can efficiently classify spectra of an unknown rock. The Mahalanobis distance gives overall better performances and is easier to manage than the Manhattan distance for which the determination of the cut-off distance is not easy. However these two techniques are complementary and their analytical performances will improve with time during MSL operations as the quantity of available Martian spectra will grow. The analysis accuracy and performances will benefit from a combination of the two approaches. - Highlights: • We use a novel independent component analysis method to classify LIBS spectra. • We demonstrate the usefulness of ICA. • We report the performances of the ICA classification. • We compare it to other classical classification schemes

  3. Luminosity Coincident with Initial Breakdown Pulses in Lightning

    Science.gov (United States)

    Stolzenburg, M.; Marshall, T.; Karunarathne, S.; Karunarathna, N.; Vickers, L.; Warner, T. A.; Orville, R. E.; Betz, H.

    2012-12-01

    Time correlated high-speed video and electromagnetic data for 15 cloud-to-ground and intracloud lightning flashes reveal bursts of light, bright enough to be seen through intervening cloud, during the initial breakdown (IB) stage and within the first 3 ms after flash initiation. Each sudden increase in luminosity is coincident with a CG-type (12 cases) or IC-type (3 cases) IB pulse in fast electric field change records. Some of these IB pulses have a coincident VLF/LF (LINET) or a VHF (LDAR2) radiation source. The luminosity bursts of 14 CG flashes occur 11-340 ms before the first return stroke, at altitudes of 4-8 km, and at 4-41 km range from the camera. In seven cases, streamer-type linear segments visibly advance away from the first light burst for 55-200 μs, then the entire length dims, then the luminosity sequence repeats along the same path. These visible initial streamers lengthen intermittently to about 300-1500 m. Their estimated 2-D speeds are 4 to 18 x 10^5 m/s over the first few hundred microseconds and decrease by about 50% over the first 2 ms. In other cases, only a bright spot or a broad area of diffuse light, presumably scattered by intervening cloud, is visible. The bright area grows larger over 20-60 μs before the luminosity fades in about 100 μs, then this sequence may repeat several times. In several of the flashes a 1-2 ms period of little or no luminosity and small E-change is observed following the IB stage prior to stepped leader development. In this presentation we will show examples of the IB luminosity and coincident electromagnetic data.

  4. Detection of uranium using laser-induced breakdown spectroscopy.

    Science.gov (United States)

    Chinni, Rosemarie C; Cremers, David A; Radziemski, Leon J; Bostian, Melissa; Navarro-Northrup, Claudia

    2009-11-01

    The goal of this work is a detailed study of uranium detection by laser-induced breakdown spectroscopy (LIBS) for application to activities associated with environmental surveillance and detecting weapons of mass destruction (WMD). The study was used to assist development of LIBS instruments for standoff detection of bulk radiological and nuclear materials and these materials distributed as contaminants on surfaces. Uranium spectra were analyzed under a variety of different conditions at room pressure, reduced pressures, and in an argon atmosphere. All spectra displayed a high apparent background due to the high density of uranium lines. Time decay curves of selected uranium lines were monitored and compared to other elements in an attempt to maximize detection capabilities for each species in the complicated uranium spectrum. A survey of the LIBS uranium spectra was conducted and relative emission line strengths were determined over the range of 260 to 800 nm. These spectra provide a guide for selection of the strongest LIBS analytical lines for uranium detection in different spectral regions. A detection limit for uranium in soil of 0.26% w/w was obtained at close range and 0.5% w/w was achieved at a distance of 30 m. Surface detection limits were substrate dependent and ranged from 13 to 150 microg/cm2. Double-pulse experiments (both collinear and orthogonal arrangements) were shown to enhance the uranium signal in some cases. Based on the results of this work, a short critique is given of the applicability of LIBS for the detection of uranium residues on surfaces for environmental monitoring and WMD surveillance. PMID:19891832

  5. Independent component analysis classification of laser induced breakdown spectroscopy spectra

    Energy Technology Data Exchange (ETDEWEB)

    Forni, Olivier, E-mail: olivier.forni@irap.omp.eu [Université de Toulouse, UPS-OMP, Institut de Recherche en Astrophysiqe et Planétologie, Toulouse (France); CNRS, IRAP, 9, av. Colonel Roche, BP 44346, F-31028 Cedex 4, Toulouse (France); Maurice, Sylvestre, E-mail: sylvestre.maurice@irap.omp.eu [Université de Toulouse, UPS-OMP, Institut de Recherche en Astrophysiqe et Planétologie, Toulouse (France); CNRS, IRAP, 9, av. Colonel Roche, BP 44346, F-31028 Cedex 4, Toulouse (France); Gasnault, Olivier, E-mail: olivier.gasnault@irap.omp.eu [Université de Toulouse, UPS-OMP, Institut de Recherche en Astrophysiqe et Planétologie, Toulouse (France); CNRS, IRAP, 9, av. Colonel Roche, BP 44346, F-31028 Cedex 4, Toulouse (France); Wiens, Roger C., E-mail: rwiens@lanl.gov [Space Remote Sensing, Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Cousin, Agnès, E-mail: acousin@lanl.gov [Université de Toulouse, UPS-OMP, Institut de Recherche en Astrophysiqe et Planétologie, Toulouse (France); CNRS, IRAP, 9, av. Colonel Roche, BP 44346, F-31028 Cedex 4, Toulouse (France); Chemical Division, Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Clegg, Samuel M., E-mail: sclegg@lanl.gov [Chemical Division, Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Sirven, Jean-Baptiste, E-mail: jean-baptiste.sirven@cea.f [CEA Saclay, DEN/DPC/SCP, 91191 Cedex, Gif sur Yvette (France); Lasue, Jérémie, E-mail: jeremie.lasue@irap.omp.eu [Université de Toulouse, UPS-OMP, Institut de Recherche en Astrophysiqe et Planétologie, Toulouse (France); CNRS, IRAP, 9, av. Colonel Roche, BP 44346, F-31028 Cedex 4, Toulouse (France)

    2013-08-01

    The ChemCam instrument on board Mars Science Laboratory (MSL) rover uses the laser-induced breakdown spectroscopy (LIBS) technique to remotely analyze Martian rocks. It retrieves spectra up to a distance of seven meters to quantify and to quantitatively analyze the sampled rocks. Like any field application, on-site measurements by LIBS are altered by diverse matrix effects which induce signal variations that are specific to the nature of the sample. Qualitative aspects remain to be studied, particularly LIBS sample identification to determine which samples are of interest for further analysis by ChemCam and other rover instruments. This can be performed with the help of different chemometric methods that model the spectra variance in order to identify a the rock from its spectrum. In this paper we test independent components analysis (ICA) rock classification by remote LIBS. We show that using measures of distance in ICA space, namely the Manhattan and the Mahalanobis distance, we can efficiently classify spectra of an unknown rock. The Mahalanobis distance gives overall better performances and is easier to manage than the Manhattan distance for which the determination of the cut-off distance is not easy. However these two techniques are complementary and their analytical performances will improve with time during MSL operations as the quantity of available Martian spectra will grow. The analysis accuracy and performances will benefit from a combination of the two approaches. - Highlights: • We use a novel independent component analysis method to classify LIBS spectra. • We demonstrate the usefulness of ICA. • We report the performances of the ICA classification. • We compare it to other classical classification schemes.

  6. Analysis of slags using laser-induced breakdown spectroscopy

    Science.gov (United States)

    Sanghapi, Hervé K.; Ayyalasomayajula, Krishna K.; Yueh, Fang Y.; Singh, Jagdish P.; McIntyre, Dustin L.; Jain, Jinesh C.; Nakano, Jinichiro

    2016-01-01

    The feasibility of laser-induced breakdown spectroscopy (LIBS) for the analysis of gasification slags was investigated by comparing LIBS results to the results of an ICP-OES analyzer. A small amount of slag sample was placed on a piece of double sided adhesive tape attached to a glass microscope slide and analyzed for Al, Ca, Fe, Si, and V which are major elements found in slags. The partial least squares regression (PLS-R) and univariate simple linear regression (SLR) calibration methods indicated that apart from V (accuracy up to + 20%) the accuracy of analysis varies within 0.35-6.5% for SLR and 0.06-10% for PLS-R. A paired-sample t-test within the 95% confidence level yielded p-values greater than 0.05, meaning no appreciable statistical difference was observed between the univariate SLR with internal standardization and the multivariate PLS-R for most of the analytes. From the results obtained in this work, LIBS response varies depending on the element and the technique used for quantitative analysis. Simultaneous use of the univariate calibration curves with internal standard (intensity ratio) and PLS regression in multi-elemental analysis can help reduce the matrix effect of slags associated to their high variation in concentration. Overall, these results demonstrate the capability of LIBS as an alternative technique for analyzing gasification slags. Estimated limits of detection for Al, Ca, Fe, Si and V were 0.167, 0.78, 0.171, 0.243 and 0.01 wt.%, respectively.

  7. Quantitative Remote Laser-Induced Breakdown Spectroscopy by Multivariate Analysis

    Science.gov (United States)

    Clegg, S. M.; Sklute, E. C.; Dyar, M. D.; Barefield, J. E.; Wiens, R. C.

    2007-12-01

    The ChemCam instrument selected for the Mars Science Laboratory (MSL) rover includes a remote Laser- Induced Breakdown Spectrometer (LIBS) that will quantitatively probe samples up to 9m from the rover mast. LIBS is fundamentally an elemental analysis technique. LIBS involves focusing a Nd:YAG laser operating at 1064 nm onto the surface of the sample. The laser ablates material from the surface, generating an expanding plasma containing electronically excited ions, atoms, and small molecules. As these electronically excited species relax back to the ground state, they emit light at wavelengths characteristic of the species present in the sample. Some of this emission is directed into one of three dispersive spectrometers. In this paper, we studied a suite of 18 igneous and highly-metamorphosed samples from a wide variety of parageneses for which chemical analyses by XRF were already available. Rocks were chosen to represent a range of chemical composition from basalt to rhyolite, thus providing significant variations in all of the major element contents (Si, Fe, Al, Ca, Na, K, O, Ti, Mg, and Mn). These samples were probed at a 9m standoff distance under experimental conditions that are similar to ChemCam. Extracting quantitative elemental concentrations from LIBS spectra is complicated by the chemical matrix effects. Conventional methods for obtaining quantitative chemical data from LIBS analyses are compared with new multivariate analysis (MVA) techniques that appear to compensate for these chemical matrix effects. The traditional analyses use specific elemental peak heights or areas, which compared with calibration curves for each element at one or more emission lines for a series of standard samples. Because of matrix effects, the calibration standards generally must have similar chemistries to the unknown samples, and thus this conventional approach imposes severe limitations on application of the technique to remote analyses. In this suite of samples, the use

  8. Effect of BaTiO3 nano-particles on breakdown performance of propylene carbonate

    Science.gov (United States)

    Hou, Yanpan; Zhang, Zicheng; Zhang, Jiande; Liu, Zhuofeng; Song, Zuyin

    2015-05-01

    As an alternative to water, propylene carbonate (PC) has a good application prospect in the compact pulsed power sources for its breakdown strength higher than that of water, resistivity bigger than 109 Ω m, and low freezing temperature (-49 °C). In this paper, the investigation into dielectric breakdown of PC and PC-based nano-fluids (NFs) subjected to high amplitude electric field is presented with microsecond pulses applied to a 1 mm gap full of PC or NFs between spherical electrodes. One kind of NF is composed of PC mixed with 0.5-1.4 vol. % BaTiO3 (BT) nano-particles of mean diameter ≈100 nm and another is mixed with 0.3-0.8 vol. % BT nano-particles of mean diameter ≈30 nm. The experimental results demonstrate the rise of permittivity and improvement of the breakdown strength of NFs compared with PC. Moreover, it is found that there exists an optimum fraction for these NFs corresponding to tremendous surface area in nano-composites with finite mesoscopic thickness. In concrete, the dielectric breakdown voltage of NFs is 33% higher than that of PC as the volume concentration of nano-particles with a 100 nm diameter is 0.9% and the breakdown voltage of NFs is 40% higher as the volume concentration of nano-particles with a 30 nm diameter is 0.6%. These phenomena are considered as the dielectric breakdown voltage of PC-based NFs is increased because the interfaces between nano-fillers and PC matrices provide myriad trap sites for charge carriers, which play a dominant role in the breakdown performance of NFs.

  9. Dielectric breakdown in silica-amorphous polymer nanocomposite films: the role of the polymer matrix.

    Science.gov (United States)

    Grabowski, Christopher A; Fillery, Scott P; Westing, Nicholas M; Chi, Changzai; Meth, Jeffrey S; Durstock, Michael F; Vaia, Richard A

    2013-06-26

    The ultimate energy storage performance of an electrostatic capacitor is determined by the dielectric characteristics of the material separating its conductive electrodes. Polymers are commonly employed due to their processability and high breakdown strength; however, demands for higher energy storage have encouraged investigations of ceramic-polymer composites. Maintaining dielectric strength, and thus minimizing flaw size and heterogeneities, has focused development toward nanocomposite (NC) films; but results lack consistency, potentially due to variations in polymer purity, nanoparticle surface treatments, nanoparticle size, and film morphology. To experimentally establish the dominant factors in broad structure-performance relationships, we compare the dielectric properties for four high-purity amorphous polymer films (polymethyl methacrylate, polystyrene, polyimide, and poly-4-vinylpyridine) incorporating uniformly dispersed silica colloids (up to 45% v/v). Factors known to contribute to premature breakdown-field exclusion and agglomeration-have been mitigated in this experiment to focus on what impact the polymer and polymer-nanoparticle interactions have on breakdown. Our findings indicate that adding colloidal silica to higher breakdown strength amorphous polymers (polymethyl methacrylate and polyimide) causes a reduction in dielectric strength as compared to the neat polymer. Alternatively, low breakdown strength amorphous polymers (poly-4-vinylpyridine and especially polystyrene) with comparable silica dispersion show similar or even improved breakdown strength for 7.5-15% v/v silica. At ∼15% v/v or greater silica content, all the polymer NC films exhibit breakdown at similar electric fields, implying that at these loadings failure becomes independent of polymer matrix and is dominated by silica. PMID:23639183

  10. Spectrographic approach for the diagnosis of rf breakdown in accelerating rf structures

    Energy Technology Data Exchange (ETDEWEB)

    Tomizawa, H.; Taniuchi, T.; Hanaki, H.; Igarashi, Y.; Yamaguchi, S.; Enomoto, A

    2004-07-31

    The acceleration gradient of an electron linac is limited by rf breakdown in its accelerating structure. We applied an imaging spectrograph system to study the mechanism of rf breakdown phenomena in accelerating rf structures. Excited gases released from the surface emit light during rf breakdown with the type of gases dependent upon surface treatments and rinsing methods. To study rf breakdown, we used 2-m-long accelerating structures and investigated the effects of a high-pressure ultrapure water rinsing (HPR) treatment applied to these rf structures. We performed experiments to study the gases released from the surface of rf structures with quadrupole mass spectroscopy and imaging spectrography of atomic lines. As a result, just after rf breakdown, we could observe instantly increasing signals at mass numbers 2 (H{sub 2}), 28 (CO), and 44 (CO{sub 2}), but not 18 (H{sub 2}O). We also conducted spectral imaging of the light emissions from the atoms and ions in a vacuum excited through rf breakdown. Using an accelerating structure without HPR treatment, we observed atomic lines at 511 nm (Cu I), 622 nm (Cu II), and 711 nm (C I). With HPR treatment, the atomic lines were observed at 395 nm (O I), 459 nm (O II), 511 nm (Cu I), 538 nm (C I), 570 nm (Cu I), 578 nm (Cu I), 656 nm (H: Balmer alpha), and 740 nm (Cu II). In an additional surface analysis, we found carbon as the most dominant element, with the exception of copper, on the blackened surface of the rf-conditioned accelerating structure without HPR treatment. Based on these experiments, we concluded that some components of the plasma can affect a copper surface. We also have provided a phenomenological review of our experimental results and a simple explanation of rf conditioning with rf breakdown.

  11. Epidemiological investigation of bovine tuberculosis herd breakdowns in Spain 2009/2011.

    Directory of Open Access Journals (Sweden)

    Sintayehu Guta

    Full Text Available We analyzed the most likely cause of 687 bovine tuberculosis (bTB breakdowns detected in Spain between 2009 and 2011 (i.e., 22% of the total number of breakdowns detected during this period. Seven possible causes were considered: i residual infection; ii introduction of infected cattle from other herds; iii sharing of pastures with infected herds; iv contiguous spread from infected neighbor herds; v presence of infected goats in the farm; vi interaction with wildlife reservoirs and vii contact with an infected human. For each possible cause a decision tree was developed and key questions were included in each of them. Answers to these key questions lead to different events within each decision tree. In order to assess the likelihood of occurrence of the different events a qualitative risk assessment approach was used. For this purpose, an expert opinion workshop was organized and ordinal values, ranging from 0 to 9 (i.e., null to very high likelihood of occurrence were assigned. The analysis identified residual infection as the most frequent cause of bTB breakdowns (22.3%; 95%CI: 19.4-25.6, followed by interaction with wildlife reservoirs (13.1%; 95%CI: 10.8-15.8. The introduction of infected cattle, sharing of pastures and contiguous spread from infected neighbour herds were also identified as relevant causes. In 41.6% (95%CI: 38.0-45.4 of the breakdowns the origin of infection remained unknown. Veterinary officers conducting bTB breakdown investigations have to state their opinion about the possible cause of each breakdown. Comparison between the results of our analysis and the opinion from veterinary officers revealed a slight concordance. This slight agreement might reflect a lack of harmonized criteria to assess the most likely cause of bTB breakdowns as well as different perceptions about the importance of the possible causes. This is especially relevant in the case of the role of wildlife reservoirs.

  12. Spectrographic approach for the diagnosis of rf breakdown in accelerating rf structures

    International Nuclear Information System (INIS)

    The acceleration gradient of an electron linac is limited by rf breakdown in its accelerating structure. We applied an imaging spectrograph system to study the mechanism of rf breakdown phenomena in accelerating rf structures. Excited gases released from the surface emit light during rf breakdown with the type of gases dependent upon surface treatments and rinsing methods. To study rf breakdown, we used 2-m-long accelerating structures and investigated the effects of a high-pressure ultrapure water rinsing (HPR) treatment applied to these rf structures. We performed experiments to study the gases released from the surface of rf structures with quadrupole mass spectroscopy and imaging spectrography of atomic lines. As a result, just after rf breakdown, we could observe instantly increasing signals at mass numbers 2 (H2), 28 (CO), and 44 (CO2), but not 18 (H2O). We also conducted spectral imaging of the light emissions from the atoms and ions in a vacuum excited through rf breakdown. Using an accelerating structure without HPR treatment, we observed atomic lines at 511 nm (Cu I), 622 nm (Cu II), and 711 nm (C I). With HPR treatment, the atomic lines were observed at 395 nm (O I), 459 nm (O II), 511 nm (Cu I), 538 nm (C I), 570 nm (Cu I), 578 nm (Cu I), 656 nm (H: Balmer alpha), and 740 nm (Cu II). In an additional surface analysis, we found carbon as the most dominant element, with the exception of copper, on the blackened surface of the rf-conditioned accelerating structure without HPR treatment. Based on these experiments, we concluded that some components of the plasma can affect a copper surface. We also have provided a phenomenological review of our experimental results and a simple explanation of rf conditioning with rf breakdown

  13. Improvement in the breakdown endurance of high-κ dielectric by utilizing stacking technology and adding sufficient interfacial layer

    Science.gov (United States)

    2014-01-01

    Improvement in the time-zero dielectric breakdown (TZDB) endurance of metal-oxide-semiconductor (MOS) capacitor with stacking structure of Al/HfO2/SiO2/Si is demonstrated in this work. The misalignment of the conduction paths between two stacking layers is believed to be effective to increase the breakdown field of the devices. Meanwhile, the resistance of the dielectric after breakdown for device with stacking structure would be less than that of without stacking structure due to a higher breakdown field and larger breakdown power. In addition, the role of interfacial layer (IL) in the control of the interface trap density (Dit) and device reliability is also analyzed. Device with a thicker IL introduces a higher breakdown field and also a lower Dit. High-resolution transmission electron microscopy (HRTEM) of the samples with different IL thicknesses is provided to confirm that IL is needed for good interfacial property. PMID:25246869

  14. Cholecystokinin receptors: disparity between phosphoinositide breakdown and amylase releasing activity of CCK analogues in pancreas

    International Nuclear Information System (INIS)

    Cholecystokinin (CCK) peptides are a family of hormones which also occur in brain. In pancreas CCK stimulates the release of amylase, a process that is dependent on the mobilization of intracellular Ca2+. Recent evidence suggests that inositol 1,4,5-trisphosphate, the breakdown product of phosphatidylinositol 4,5-bisphosphate, is responsible for the rise in intracellular Ca2+. Their laboratory has developed assays to study synthetic CCK analogues using radioligand binding, PI breakdown and amylase release. They have shown that there are good correlations among these three assay systems for the carboxy terminal fragments of CCK8. Recently, they have discovered synthetic analogues of CCK4 that are full agonists in amylase release but are ineffective in causing PI breakdown. In particular, A-61576, Boc-5-amino-2-indolemethylene-pent-2-ene-1-oyl-Leu-Asp-Phe-NH2, is a full agonist in the amylase releasing assay, but is devoid of PI stimulating activity. A-61576 completely reverses the stimulation of PI response induced by CCK8, indicative of an antagonist. Since a mechanism other than the PI breakdown is responsible for amylase release by A-61576, they suggest that separate receptors are responsible for PI breakdown and amylase release

  15. The probability of electrical breakdown: evidence for a transition between the townsend and streamer mechanisms

    International Nuclear Information System (INIS)

    The probability that an electron initiates breakdown has been investigated by measurements of spark delay times in a uniform field gap provided with a small photocurrent of free electrons. In N2, H2, and Ar the dependence of the breakdown probability on overvoltage agreed with calculations based on the Townsend mechanism. In SF6 and CC12F2 a transition was observed with increasing pressure from a dependence that agreed with the Townsend theory to a more gradual rise with voltage. This transition has been ascribed to a decrease in the secondary ionization coefficient with increasing pressure, which resulted in an average electron avalanche size at the static breakdown voltage that approached the critical value for streamer formation. A unified breakdown probability theory, for which the Townsend and streamer mechanisms are limiting cases, has been developed to account for the data over the full pressure range. The implications of these results for measurement of the static breakdown voltage and the secondary ionization coefficient are discussed

  16. Field emission driven direct current argon discharges and electrical breakdown mechanism across micron scale gaps

    Science.gov (United States)

    Matejčik, Štefan; Radjenović, Branislav; Klas, Matej; Radmilović-Radjenović, Marija

    2015-11-01

    In this paper results of the experimental and theoretical studies of the field emission driven direct current argon microdischarges for the gaps between 1 μm and 100 μm are presented and discussed. The breakdown voltage curves and Volt-Ampere characteristics proved to be a fertile basis providing better understanding of the breakdown phenomena in microgaps. Based on the measured breakdown voltage curves, the effective yields have been estimated confirming that the secondary electron emission due to high electric field generated in microgaps depends primarily on the electric field leading directly to the violation of the Paschen's law. Experimental data are supported by the theoretical predictions that suggest departure from the scaling law and a flattening of the Paschen curves at higher pressures confirming that Townsend phenomenology breaks down when field emission becomes the key mechanism leading to the breakdown. Field emission of electrons from the cathode, the space charge effects in the breakdown and distinction between the Fowler-Nordheim field emission and the space charge limited current density are also analyzed. Images and Volt-Ampere characteristics recorded at the electrode gap size of 20 μm indicate the existence of a discharge region similar to arc at the pressure of around 200 Torr has been observed. Contribution to the Topical Issue "Recent Breakthroughs in Microplasma Science and Technology", edited by Kurt Becker, Jose Lopez, David Staack, Klaus-Dieter Weltmann and Wei Dong Zhu.

  17. Degradation characteristics of 2G HTS tapes with respect to an electrical breakdown

    International Nuclear Information System (INIS)

    The electrical insulation design for a superconducting coil system is important for developing high voltage superconducting apparatuses. Also, the degraded characteristics of superconducting tapes due to an electrical breakdown should be considered for superconducting coils design. In this study, the degradation characteristics of 2G high temperature superconducting (HTS) tapes were studied with respect to electrical breakdown tests. The degradation tests of 2G HTS tapes were performed with various stabilizer materials. The degradation characteristics of 2G HTS tapes such as critical current(Ic) and index number were observed by performing electrical breakdown tests. It was found that the characteristics such as Ic and index number can be degraded by an electrical breakdown. Moreover, it was concluded that the degradation characteristics of 2G HTS tapes were affected by a stabilizer material and applied breakdown voltage. The cross sectional view of 2G HTS tapes was observed by using a scanning electron microscope (SEM). As results, it is found that the degradation characteristics of 2G HTS tapes are concerned with hardness and electrical resistivity of stabilizer layers

  18. High stored-energy breakdown tests on electrodes made of stainless steel, copper, titanium and molybdenum

    International Nuclear Information System (INIS)

    IRFM have conducted resilience tests on electrodes made of Cu, stainless steel 304L, Ti and Mo against breakdowns up to 170 kV and 300 J. The tests of the 10×10 cm2 electrodes have been performed at an electrode distance d=11 mm under vacuum (P∼5×10−6 mbar). No great difference in voltage holding between the materials could be identified; all materials could reach a voltage holding between 140 and 170 kV over the 11 mm gap, i.e. results scatter within a ±10% band. After exposure to ∼10000 seconds of high-voltage (HV) on-time, having accumulated ∼1000 breakdowns, the electrodes were inspected. The anodes were covered with large and small craters. The rugosity of the anodes had increased substantially, that of the cathodes to a lesser extent. The molybdenum electrodes are least affected, but this does not show in their voltage holding capability. It is hypothesized that penetrating high-energy electrons from the breakdown project heat below the surface of the anode and cause a micro-explosion of material when melting point is exceeded. Polished electrodes have also been tested. The polishing results in a substantially reduced breakdown rate in the beginning, but after having suffered a relatively small number (∼100) of breakdowns, the polished electrodes behaved the same as the unpolished ones

  19. Optimization of laser-induced breakdown spectroscopy for coal powder analysis with different particle flow diameters

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Shunchun, E-mail: epscyao@scut.edu.cn [School of Electric Power, South China University of Technology, Guangzhou, Guangdong 510640 (China); State Key Laboratory of Pulsed Power Laser Technology, Electronic Engineering Institute, Hefei 230037 (China); Xu, Jialong; Dong, Xuan; Zhang, Bo; Zheng, Jianping [School of Electric Power, South China University of Technology, Guangzhou, Guangdong 510640 (China); Lu, Jidong, E-mail: jdlu@scut.edu.cn [School of Electric Power, South China University of Technology, Guangzhou, Guangdong 510640 (China)

    2015-08-01

    The on-line measurement of coal is extremely useful for emission control and combustion process optimization in coal-fired plant. Laser-induced breakdown spectroscopy was employed to directly analyze coal particle flow. A set of tapered tubes were proposed for beam-focusing the coal particle flow to different diameters. For optimizing the measurement of coal particle flow, the characteristics of laser-induced plasma, including optical breakdown, the relative standard deviation of repeated measurement, partial breakdown spectra ratio and line intensity, were carefully analyzed. The comparison of the plasma characteristics among coal particle flow with different diameters showed that air breakdown and the random change in plasma position relative to the collection optics could significantly influence on the line intensity and the reproducibility of measurement. It is demonstrated that the tapered tube with a diameter of 5.5 mm was particularly useful to enrich the coal particles in laser focus spot as well as to reduce the influence of air breakdown and random changes of plasma in the experiment. - Highlights: • Tapered tube was designed for beam-focusing the coal particle flow as well as enriching the particles in laser focus spot. • The characteristics of laser-induced plasma of coal particle flow were investigated carefully. • An appropriate diameter of coal particle flow was proven to benefit for improving the performance of LIBS measurement.

  20. High stored-energy breakdown tests on electrodes made of stainless steel, copper, titanium and molybdenum

    Energy Technology Data Exchange (ETDEWEB)

    Esch, H. P. L. de, E-mail: hubert.de-esch@cea.fr; Simonin, A.; Grand, C. [CEA-Cadarache, IRFM, F-13108 St. Paul-lez-Durance (France)

    2015-04-08

    IRFM have conducted resilience tests on electrodes made of Cu, stainless steel 304L, Ti and Mo against breakdowns up to 170 kV and 300 J. The tests of the 10×10 cm{sup 2} electrodes have been performed at an electrode distance d=11 mm under vacuum (P∼5×10{sup −6} mbar). No great difference in voltage holding between the materials could be identified; all materials could reach a voltage holding between 140 and 170 kV over the 11 mm gap, i.e. results scatter within a ±10% band. After exposure to ∼10000 seconds of high-voltage (HV) on-time, having accumulated ∼1000 breakdowns, the electrodes were inspected. The anodes were covered with large and small craters. The rugosity of the anodes had increased substantially, that of the cathodes to a lesser extent. The molybdenum electrodes are least affected, but this does not show in their voltage holding capability. It is hypothesized that penetrating high-energy electrons from the breakdown project heat below the surface of the anode and cause a micro-explosion of material when melting point is exceeded. Polished electrodes have also been tested. The polishing results in a substantially reduced breakdown rate in the beginning, but after having suffered a relatively small number (∼100) of breakdowns, the polished electrodes behaved the same as the unpolished ones.

  1. Quantitative Determination of the Breakdown Field of Air from Van de Graaff Generator Discharge

    Science.gov (United States)

    Beach, John; Chartrand, Bridget; Gallagher, Hugh

    2016-03-01

    The Van de Graaff generator (VG) is ubiquitous in electrostatic demonstrations because of the large static charge and dramatic sparks produced. We have developed a novel technique for determining the breakdown field of air using the VG. When a spark occurs, the force of attraction between the VG and a discharge sphere suspended above it is measured by a Pasco force sensor. At this time the charge is not symmetric but pulled towards the near side of the spheres by mutual attraction. In order to interpret the measured force in terms of the breakdown field, an accurate model of the charge distribution is needed. Using the method of images for a spherical conductor in an iterative fashion we can provide this model. The electric field in the vicinity of the spheres is then calculated from the charge distribution and its maximum value is the breakdown field. In preliminary work, we determined the breakdown field to be 3.1x106 N/C at 24.9 C and 18% relative humidity. We will report our most recent determination of the breakdown field using this method and discuss the validity of the results in terms of accepted values, experimental limitations and sensitivity to the charge distribution model.

  2. Optimization of laser-induced breakdown spectroscopy for coal powder analysis with different particle flow diameters

    International Nuclear Information System (INIS)

    The on-line measurement of coal is extremely useful for emission control and combustion process optimization in coal-fired plant. Laser-induced breakdown spectroscopy was employed to directly analyze coal particle flow. A set of tapered tubes were proposed for beam-focusing the coal particle flow to different diameters. For optimizing the measurement of coal particle flow, the characteristics of laser-induced plasma, including optical breakdown, the relative standard deviation of repeated measurement, partial breakdown spectra ratio and line intensity, were carefully analyzed. The comparison of the plasma characteristics among coal particle flow with different diameters showed that air breakdown and the random change in plasma position relative to the collection optics could significantly influence on the line intensity and the reproducibility of measurement. It is demonstrated that the tapered tube with a diameter of 5.5 mm was particularly useful to enrich the coal particles in laser focus spot as well as to reduce the influence of air breakdown and random changes of plasma in the experiment. - Highlights: • Tapered tube was designed for beam-focusing the coal particle flow as well as enriching the particles in laser focus spot. • The characteristics of laser-induced plasma of coal particle flow were investigated carefully. • An appropriate diameter of coal particle flow was proven to benefit for improving the performance of LIBS measurement

  3. High stored-energy breakdown tests on electrodes made of stainless steel, copper, titanium and molybdenum

    Science.gov (United States)

    de Esch, H. P. L.; Simonin, A.; Grand, C.

    2015-04-01

    IRFM have conducted resilience tests on electrodes made of Cu, stainless steel 304L, Ti and Mo against breakdowns up to 170 kV and 300 J. The tests of the 10×10 cm2 electrodes have been performed at an electrode distance d=11 mm under vacuum (P˜5×10-6 mbar). No great difference in voltage holding between the materials could be identified; all materials could reach a voltage holding between 140 and 170 kV over the 11 mm gap, i.e. results scatter within a ±10% band. After exposure to ˜10000 seconds of high-voltage (HV) on-time, having accumulated ˜1000 breakdowns, the electrodes were inspected. The anodes were covered with large and small craters. The rugosity of the anodes had increased substantially, that of the cathodes to a lesser extent. The molybdenum electrodes are least affected, but this does not show in their voltage holding capability. It is hypothesized that penetrating high-energy electrons from the breakdown project heat below the surface of the anode and cause a micro-explosion of material when melting point is exceeded. Polished electrodes have also been tested. The polishing results in a substantially reduced breakdown rate in the beginning, but after having suffered a relatively small number (˜100) of breakdowns, the polished electrodes behaved the same as the unpolished ones.

  4. Short-pulse high-power microwave breakdown at high pressures

    International Nuclear Information System (INIS)

    The fluid model is proposed to investigate the gas breakdown driven by a short-pulse (such as a Gaussian pulse) high-power microwave at high pressures. However, the fluid model requires specification of the electron energy distribution function (EEDF); the common assumption of a Maxwellian EEDF can result in the inaccurate breakdown prediction when the electrons are not in equilibrium. We confirm that the influence of the incident pulse shape on the EEDF is tiny at high pressures by using the particle-in-cell Monte Carlo collision (PIC-MCC) model. As a result, the EEDF for a rectangular microwave pulse directly derived from the Boltzmann equation solver Bolsig+ is introduced into the fluid model for predicting the breakdown threshold of the non-rectangular pulse over a wide range of pressures, and the obtained results are very well matched with those of the PIC-MCC simulations. The time evolution of a non-rectangular pulse breakdown in gas, obtained by the fluid model with the EEDF from Bolsig+, is presented and analyzed at different pressures. In addition, the effect of the incident pulse shape on the gas breakdown is discussed. (paper)

  5. Short-pulse high-power microwave breakdown at high pressures

    Institute of Scientific and Technical Information of China (English)

    赵朋程; 廖成; 冯菊

    2015-01-01

    The fluid model is proposed to investigate the gas breakdown driven by the short-pulse (such as Gaussian pulse) high-power microwave at high pressures. However, the fluid model requires specification of the electron energy distribution function (EEDF);the common assumption of a Maxwellian EEDF can result in the inaccurate breakdown prediction when the electrons are not in equilibrium. We confirm that the influence of the incident pulse shape on the EEDF is tiny at high pressures by using the particle-in-cell Monte Carlo collision (PIC-MCC) model. As a result, the EEDF for a rectangular microwave pulse directly derived from the Boltzmann equation solver Bolsig+, is introduced into the fluid model for predicting the breakdown threshold of the non-rectangular pulse over a wide range of pressures, and the obtained results are very well matched with those of the PIC-MCC simulations. The time evolution of a non-rectangular pulse breakdown in gas, obtained by the fluid model with the EEDF from Bolsig+, is presented and analyzed at different pressures. In addition, the effect of the incident pulse shape on the gas breakdown is discussed.

  6. Nuclear envelope breakdown induced by herpes simplex virus type 1 involves the activity of viral fusion proteins

    International Nuclear Information System (INIS)

    Herpesvirus infection reorganizes components of the nuclear lamina usually without loss of integrity of the nuclear membranes. We report that wild-type HSV infection can cause dissolution of the nuclear envelope in transformed mouse embryonic fibroblasts that do not express torsinA. Nuclear envelope breakdown is accompanied by an eight-fold inhibition of virus replication. Breakdown of the membrane is much more limited during infection with viruses that lack the gB and gH genes, suggesting that breakdown involves factors that promote fusion at the nuclear membrane. Nuclear envelope breakdown is also inhibited during infection with virus that does not express UL34, but is enhanced when the US3 gene is deleted, suggesting that envelope breakdown may be enhanced by nuclear lamina disruption. Nuclear envelope breakdown cannot compensate for deletion of the UL34 gene suggesting that mixing of nuclear and cytoplasmic contents is insufficient to bypass loss of the normal nuclear egress pathway. - Highlights: • We show that wild-type HSV can induce breakdown of the nuclear envelope in a specific cell system. • The viral fusion proteins gB and gH are required for induction of nuclear envelope breakdown. • Nuclear envelope breakdown cannot compensate for deletion of the HSV UL34 gene

  7. Surface Analysis of OFE-Copper X-Band Accelerating Structures and Possible Correlation to RF Breakdown Events

    CERN Document Server

    Harvey, S E; Kirby, R E; Marcelja, F; Adamson, K; Garwin, E L

    2003-01-01

    X-band accelerator structures meeting the Next Linear Collider (NLC) design requirements have been found to suffer vacuum surface damage caused by radio frequency (RF) breakdown, when processed to high electric-field gradients. Improved understanding of these breakdown events is desirable for the development of structure designs, fabrication procedures, and processing techniques that minimize structure damage. RF reflected wave analysis and acoustic sensor pickup have provided breakdowns localization in RF structures. Particle contaminations found following clean autopsy of four RF-processed travelling wave structures, have been catalogued and analyzed. Their influence on RF breakdown, as well as that of several other material-based properties, will be discussed.

  8. Nuclear envelope breakdown induced by herpes simplex virus type 1 involves the activity of viral fusion proteins

    Energy Technology Data Exchange (ETDEWEB)

    Maric, Martina; Haugo, Alison C. [Department of Microbiology, University of Iowa, Iowa City, IA 52242 (United States); Dauer, William [Department of Neurology, University of Michigan, Ann Arbor, MI 48109 (United States); Johnson, David [Department of Microbiology and Immunology, Oregon Health Sciences University, Portland, OR 97201 (United States); Roller, Richard J., E-mail: richard-roller@uiowa.edu [Department of Microbiology, University of Iowa, Iowa City, IA 52242 (United States)

    2014-07-15

    Herpesvirus infection reorganizes components of the nuclear lamina usually without loss of integrity of the nuclear membranes. We report that wild-type HSV infection can cause dissolution of the nuclear envelope in transformed mouse embryonic fibroblasts that do not express torsinA. Nuclear envelope breakdown is accompanied by an eight-fold inhibition of virus replication. Breakdown of the membrane is much more limited during infection with viruses that lack the gB and gH genes, suggesting that breakdown involves factors that promote fusion at the nuclear membrane. Nuclear envelope breakdown is also inhibited during infection with virus that does not express UL34, but is enhanced when the US3 gene is deleted, suggesting that envelope breakdown may be enhanced by nuclear lamina disruption. Nuclear envelope breakdown cannot compensate for deletion of the UL34 gene suggesting that mixing of nuclear and cytoplasmic contents is insufficient to bypass loss of the normal nuclear egress pathway. - Highlights: • We show that wild-type HSV can induce breakdown of the nuclear envelope in a specific cell system. • The viral fusion proteins gB and gH are required for induction of nuclear envelope breakdown. • Nuclear envelope breakdown cannot compensate for deletion of the HSV UL34 gene.

  9. Electrical Breakdown Physics in Photoconductive Semiconductor Switches (PCSS).

    Energy Technology Data Exchange (ETDEWEB)

    Mar, Alan [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Zutavern, Fred J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Vawter, Gregory A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hjalmarson, Harold P. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Gallegos, Richard Joseph [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bigman, Verle Howard [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-01-01

    of 200kV (DC) and 5kA current that can be stacked in parallel to achieve 100's of kA with 10e5 shot lifetime. The new vertical switch design configuration generates parallel filaments in the bulk GaAs (as opposed to just beneath the surface as in previous designs) to achieve breakdown fields close to the maximum for the bulk GaAs while operating in air, and with 2-D scalability of the number of current-sharing filaments. This design also may be highly compatible with 2-D VCSEL arrays for optical triggering. The demonstration of this design in this LDRD utilized standard thickness wafers to trigger 0.4kA at 35kV/cm (limited by 0.6mm wafer thickness), tested to 1e5 shots with no detectable degradation of switch performance. Higher fields, total current, and switching voltages would be achievable with thicker GaAs wafers. Another important application pursued in this LDRD is the use of PCSS for trigger generator applications. Conventional in-plane PCSS have achieved triggering of a 100kV sparkgap (Kinetech-type) switch of the type similar to switches being considered for accelerator upgrades. The trigger is also being developed for pulsed power for HPM applications that require miniaturization and robust performance in noisy compact environments. This has spawned new programs for developing this technology, including an STTR for VCSEL trigger laser integration, also pursuing other follow-on applications.

  10. The quantum mechanics of ion-enhanced field emission and how it influences microscale gas breakdown

    International Nuclear Information System (INIS)

    The presence of a positive gas ion can enhance cold electron field emission by deforming the potential barrier and increasing the tunneling probability of electrons—a process known as ion-enhanced field emission. In microscale gas discharges, ion-enhanced field emission produces additional emission from the cathode and effectively reduces the voltage required to breakdown a gaseous medium at the microscale (<10 μm). In this work, we enhance classic field emission theory by determining the impact of a gaseous ion on electron tunneling and compute the effect of ion-enhanced field emission on the breakdown voltage. We reveal that the current density for ion-enhanced field emission retains the same scaling as vacuum cold field emission and that this leads to deviations from traditional breakdown theory at microscale dimensions.

  11. On the electrical breakdown of gaseous dielectrics-an engineering approach

    DEFF Research Database (Denmark)

    Pedersen, Aage

    1989-01-01

    Following an examination of the basic gas-discharge concepts, the Townsend breakdown criterion is derived for nonuniform fields and a reformulation of the streamer criterion is undertaken. A direct application of the Townsend criterion to a practical situation is hardly possible, whereas the...... streamer criterion leads to applicable criteria for the onset of breakdown in air as well as in strongly electronegative gases. In this approach, a knowledge of the relevant ionization coefficients is not required, because these are replaced by parameters obtained from uniform-field Paschen curve data. In...... addition, the criteria developed do not contain any arbitrary constants. By introducing the electrode surface mean curvature, it is shown that the calculation of breakdown data for widely different electrode shapes can be addressed through a single formula. It is emphasized that the inherent roughness of...

  12. The role of morphology and coupling of gold nanoparticles in optical breakdown during picosecond pulse exposures

    Science.gov (United States)

    Davletshin, Yevgeniy R

    2016-01-01

    Summary This paper presents a theoretical study of the interaction of a 6 ps laser pulse with uncoupled and plasmon-coupled gold nanoparticles. We show how the one-dimensional assembly of particles affects the optical breakdown threshold of its surroundings. For this purpose we used a fully coupled electromagnetic, thermodynamic and plasma dynamics model for a laser pulse interaction with gold nanospheres, nanorods and assemblies, which was solved using the finite element method. The thresholds of optical breakdown for off- and on-resonance irradiated gold nanosphere monomers were compared against nanosphere dimers, trimers, and gold nanorods with the same overall size and aspect ratio. The optical breakdown thresholds had a stronger dependence on the optical near-field enhancement than on the mass or absorption cross-section of the nanostructure. These findings can be used to advance the nanoparticle-based nanoscale manipulation of matter.

  13. Model of Reversible Breakdown in HfO2 Based on Fractal Patterns

    Directory of Open Access Journals (Sweden)

    P. Lorenzi

    2015-01-01

    Full Text Available We propose a model of the kinetics of reversible breakdown in metal-insulator-metal structures with afnia based on the growth of fractal patterns of defects when the insulator is subject to an external voltage. The probability that a defect is (or is not generated and the position where it is generated depend on the electric field distribution. The new defect moves accordingly to fractal rules and attach to another defect in a tree branch. When the two electrodes sandwiching the insulating film are connected a conductive filament is formed and the breakdown takes place. The model is calibrated with experiments inducing metastable soft breakdown events in Pt/HfO2/Pt capacitors.

  14. 3-D MEASUREMENT OF VORTEX BREAKDOWN IN CLOSED CYLINDRICAL CONTAINER VIA LDV

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A 3-D velocity measurement was carried out via LDV for vortex breakdown of swirling flow in a closed cylindrical container with a rotating disk. The experimental results of swirling flow at Ar=1.78 and Re=648-2527 are presented. At the axis, the axial velocity variation with Re describes the formation, development and disappearance of the vortex breakdown, which agrees with Escudiers’s conclusion. In the meridional plane, the velocity vectors show that the bubble type vortex breakdown region is a closed and low velocity circulating flow, which is fully isolated from the main flow thrown out by the rotating disk. For the peripheral velocity in the central region of the container, the maximum does not appear near the rotating top disk but near the stationary bottom disk and it varies sharply there. Numerical simulation results under the same conditions are also given in this paper.

  15. Experimental results of breakdown in 'Dena' plasma focus device

    International Nuclear Information System (INIS)

    In spite of the intense research activities on Plasma Focus devices, the physics of the initial breakdown and surface discharge phase has not been realized completely. In this paper we have analyzed the surface discharge and initial breakdown phase in Filippov-type Plasma Focus Facility 'Dena' (90 kJ, 25 kV) on the base of the current and current derivative measured signals by using Argon, Neon and Krypton as working gases at different discharge voltages and gas pressures, and the effects of working conditions (atomic weight, discharge voltage and gas pressure) on the breakdown and surface discharge phase have expressed. Also, on the base of these results, we have investigated about the relation of this phase with final pinch phase.

  16. In situ study on low-k interconnect time-dependent-dielectric-breakdown mechanisms

    International Nuclear Information System (INIS)

    An in situ transmission-electron-microscopy methodology is developed to observe time-dependent dielectric breakdown (TDDB) in an advanced Cu/ultra-low-k interconnect stack. A test structure, namely a “tip-to-tip” structure, was designed to localize the TDDB degradation in small dielectrics regions. A constant voltage is applied at 25 °C to the “tip-to-tip” structure, while structural changes are observed at nanoscale. Cu nanoparticle formation, agglomeration, and migration processes are observed after dielectric breakdown. The Cu nanoparticles are positively charged, since they move in opposite direction to the electron flow. Measurements of ionic current, using the Triangular-Voltage-Stress method, suggest that Cu migration is not possible before dielectric breakdown, unless the Cu/ultra-low-k interconnect stacks are heated to 200 °C and above

  17. Transient material properties during defect-assisted laser breakdown in deuterated potassium dihydrogen phosphate crystals

    Energy Technology Data Exchange (ETDEWEB)

    Duchateau, Guillaume, E-mail: duchateau@celia.u-bordeaux1.fr [Université de Bordeaux-CNRS-CEA, Centre Laser Intenses et Applications UMR 5107, 351 Cours de la Libération, 33405 Talence (France); Feit, Michael D.; Demos, Stavros G. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550 (United States)

    2014-03-14

    We investigate theoretically the transition from solid dielectric materials to warm solid density plasma during laser-induced breakdown in DKDP crystals (KD{sub 2}PO{sub 4}). Evidence taken from the experimentally measured wavelength dependence of the breakdown threshold suggests that the material excitation mechanisms mainly consist of a sequence of one-photon absorptions between short-lived vibronic defect states spanning the band gap with a quasi-continuum of states. The transition between excitation paths involving different number of photons yields information about the role of temperature in determining the width of the transition and corresponding threshold conduction band density prior to initiation of breakdown. This physical system is well adapted to study a plasma warming up at solid density leading to the so-called warm dense matter.

  18. Breakdown of the iron passive layer by use of the scanning electrochemical microscope

    Energy Technology Data Exchange (ETDEWEB)

    Still, J.W.; Wipf, D.O. [Mississippi State Univ., MS (United States). Dept. of Chemistry

    1997-08-01

    The scanning electrochemical microscope (SECM) is sued to generate localized corrosion at passivating iron surfaces by using the tip to generate Cl{sup {minus}} ions. Use of the SECM allows the rapid establishment of a locally aggressive chemical environment at a preselected site on the iron surface. The susceptibility for passive layer breakdown and corrosion initiation was examined as a function of the time between the start of the passive layer growth and the formation of Cl{sup {minus}} ions. The breakdown of the passive layer was found to depend strongly on the passivation potential and the site of Cl{sup {minus}} formation on the iron surface. In addition to generating Cl{sup {minus}} ions, the SECM tip was simultaneously used to detect large iron ion concentration fluctuations as corrosion began. Current fluctuations at the tip were observed and ascribed to precursors to the passive layer breakdown.

  19. Reduce of Threshold of Laser Inducing Breakdown in Atmosphere by Introducing an Electric Spark

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xian-Bin; SHI Wei; LI Hua

    2005-01-01

    @@ We report laser-generated plasmas in atmosphere with electrical spark generated by a synchronization circuit.The breakdown thresholds under the conditions that the electrical spark is used and not used are compared.The breakdown threshold has a distinct decrease after the electrical spark is used. Breakdown thresholds as afunction of atmosphere pressure have also been measured at laser wavelengths 532nm and 1064 nm for the laserpulse width of 15ns. We also discuss the principle and performances of the ionized atmosphere by Nd:YAGlaser under the condition of electrical spark introduction. Multiphoton ionization and cascade ionization playimportant roles in the whole process of atmosphere ionization. The free electron induced by electrical spark cansupply the initialization free electron number for multiphoton ionization and cascade ionization. A model forbreakdown in atmosphere, which is in good agreement with the experimental results, is described.

  20. In situ study on low-k interconnect time-dependent-dielectric-breakdown mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Boon Yeap, Kong, E-mail: KongBoon.Yeap@globalfoundries.com [GLOBALFOUNDRIES, Fab8, 400 Stonebreak Rd. Extension, Malta, New York 12020 (United States); Fraunhofer Institute for Ceramic Technologies and Systems, Maria-Reiche-Str. 2, D-01109 Dresden (Germany); Gall, Martin; Liao, Zhongquan; Sander, Christoph; Muehle, Uwe; Zschech, Ehrenfried [Fraunhofer Institute for Ceramic Technologies and Systems, Maria-Reiche-Str. 2, D-01109 Dresden (Germany); Justison, Patrick [GLOBALFOUNDRIES, Fab8, 400 Stonebreak Rd. Extension, Malta, New York 12020 (United States); Aubel, Oliver; Hauschildt, Meike; Beyer, Armand; Vogel, Norman [GLOBALFOUNDRIES Dresden Module One LLC and Co. KG, Wilschdorfer Landstr. 101, D-01109 Dresden (Germany)

    2014-03-28

    An in situ transmission-electron-microscopy methodology is developed to observe time-dependent dielectric breakdown (TDDB) in an advanced Cu/ultra-low-k interconnect stack. A test structure, namely a “tip-to-tip” structure, was designed to localize the TDDB degradation in small dielectrics regions. A constant voltage is applied at 25 °C to the “tip-to-tip” structure, while structural changes are observed at nanoscale. Cu nanoparticle formation, agglomeration, and migration processes are observed after dielectric breakdown. The Cu nanoparticles are positively charged, since they move in opposite direction to the electron flow. Measurements of ionic current, using the Triangular-Voltage-Stress method, suggest that Cu migration is not possible before dielectric breakdown, unless the Cu/ultra-low-k interconnect stacks are heated to 200 °C and above.

  1. Prediction of partial discharge and breakdown voltages in CF4 for arbitrary electrode geometries

    International Nuclear Information System (INIS)

    In literature a model was described for the simulation of the breakdown behaviour of SF6. As input parameters, results from swarm experiments—the critical field strength and the effective ionization coefficient—and thermodynamic properties are sufficient. Recently it was shown that it is possible to transfer this model to another strongly attaching gas. In this contribution the model is applied to tetrafluoromethane (CF4), which has a smaller critical field strength and is less attaching than SF6. Furthermore, the breakdown field strengths of alternating and lightning impulse voltages of different field configurations—from homogeneous to inhomogeneous fields—are predicted for CF4. A comparison to experimental results from the literature shows good agreement. Thus, the model is applicable not only to predict partial discharges and breakdown voltages in strongly attaching gases but also to gases less attaching than SF6. (paper)

  2. Note: A novel technique for analysis of aqueous solutions by laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Rusak, D. A.; Bell, Z. T. [Department of Chemistry, University of Scranton, Scranton, Pennsylvania 18510 (United States); Anthony, T. P. [Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122 (United States)

    2015-11-15

    Surface-enhanced Raman spectroscopy (SERS) substrates typically consist of gold or silver nanoparticles deposited on a non-conductive substrate. In Raman spectroscopy, the nanoparticles produce an enhancement of the electromagnetic field which, in turn, leads to greater electronic excitation of molecules in the local environment. Here, we show that these same surfaces can be used to enhance the signal-to-noise ratio obtained in laser-induced breakdown spectroscopy of aqueous solutions. In this case, the SERS substrates not only lower breakdown thresholds and lead to more efficient plasma initiation but also provide an appropriately wettable surface for the deposition of the liquid. We refer to this technique as surface-enhanced laser-induced breakdown spectroscopy.

  3. The inception of pulsed discharges in air: simulations in background fields above and below breakdown

    International Nuclear Information System (INIS)

    We investigate discharge inception in air, in uniform background electric fields above and below the breakdown threshold. We perform 3D particle simulations that include a natural level of background ionization in the form of positive and O2− ions. In background fields below breakdown, we use a strongly ionized seed of electrons and positive ions to enhance the field locally. In the region of enhanced field, we observe the growth of positive streamers, as in previous simulations with 2D plasma fluid models. The inclusion of background ionization has little effect in this case. When the background field is above the breakdown threshold, the situation is very different. Electrons can then detach from O2− and start ionization avalanches in the whole volume. These avalanches together create one extended discharge, in contrast to the ‘double-headed’ streamers found in many fluid simulations. (paper)

  4. Different scenarios for hyperbolicity breakdown in quasiperiodic area preserving twist maps.

    Science.gov (United States)

    Figueras, Jordi-Lluís; Haro, Àlex

    2015-12-01

    We present a computer-assisted numerical study of different bifurcations of saddle invariant tori in quasiperiodic area preserving twist maps. We detect three bifurcation scenarios. In the first scenario, the smooth bifurcation, the regularity of the invariant torus is preserved, and the stable and unstable invariant bundles collide smoothly. In the other scenarios, the spiky and folding breakdowns, the invariant torus looses smoothness, and the invariant bundles collide non-smoothly. In the former, the C(1) seminorm of the torus does not blow up while in the latter it does. Numerics suggest that after the breakdowns non-uniformly hyperbolic invariant objects persist. These are qualitatively different depending on the type of breakdown. Finally, using anti-integrable limit theory, we provide a proof of existence of non-uniformly hyperbolic invariant objects for systems very far from the integrable regime. PMID:26723158

  5. Measurements of breakdown voltages and V-I characteristics in selenium and tellurium vapours

    International Nuclear Information System (INIS)

    Measurements of breakdown voltages and V-I characteristics have been carried out, using co-axial cylindrical electrodes in selenium and tellurium vapours in the pressure range of 6 x 103 to 1.131 kPa. A high temperature heat-pipe apparatus developed in our laboratory for determining the electrical and plasma properties of metal vapours was used in the present study. The breakdown voltages obtained in selenium (Se) and tellurium (Te) vapours are higher than those obtained by earlier workers in mercury (Hg), sodium (Na), potassium (K), cadmium (Cd) and zinc(Zn) vapours under similar conditions. Since the studies were carried out in metals in their vapour state, the theory of gas breakdown is considered to explain the variation in the data obtained. The investigations clearly show that the V-I characteristics are pressure dependent and do not exhibit any negative current growth. (author). 13 refs. 5 figs

  6. On the detection of RF breakdowns in ICRH Resonant Double Loop antennas

    International Nuclear Information System (INIS)

    A voltage breakdown in an ion cyclotron resonance heating (ICRH) system is usually detected as an abrupt change in the module of the reflection coefficient |Γin| at the power source output. The same effect can be due to a large load variation. This paper presents the study of some new concept for detecting voltage breakdowns in ICRH Resonant Double Loop (RDL) systems, to be used in conjunction with the one identifying an arc by the detection of an excessive standing wave ratio (SWR), either at the operating frequency or within the band below the operating frequency. The method should be able to help discriminating fast load variations from voltage breakdowns in any of the in-vessel components under the torus vacuum, and therefore selecting the proper corrective action.

  7. On the detection of RF breakdowns in ICRH Resonant Double Loop antennas

    Energy Technology Data Exchange (ETDEWEB)

    El Khaldi, M. [CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France)], E-mail: mohamed.el-khaldi@cea.fr; Bosia, G. [Universita di Torino, Dipartimento di Fisica Generale, I-10125 Torino (Italy); Vulliez, K.; Magne, R. [CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France)

    2010-01-15

    A voltage breakdown in an ion cyclotron resonance heating (ICRH) system is usually detected as an abrupt change in the module of the reflection coefficient |{gamma}{sub in}| at the power source output. The same effect can be due to a large load variation. This paper presents the study of some new concept for detecting voltage breakdowns in ICRH Resonant Double Loop (RDL) systems, to be used in conjunction with the one identifying an arc by the detection of an excessive standing wave ratio (SWR), either at the operating frequency or within the band below the operating frequency. The method should be able to help discriminating fast load variations from voltage breakdowns in any of the in-vessel components under the torus vacuum, and therefore selecting the proper corrective action.

  8. Laser-induced breakdown spectroscopy detection of heavy metal in water based on graphite conch method

    Science.gov (United States)

    Wang, Chunlong; Liu, Jianguo; Zhao, Nanjing; Shi, Huan; Liu, Lituo; Ma, Mingjun; Zhang, Wei; Chen, Dong; Liu, Jing; Zhang, Yujun; Liu, Wenqing

    2012-10-01

    The laser-induced breakdown spectroscopy emission characteristics of trace heavy metal lead in water is studied based on graphite conch method, with a 1064nm wavelength Nd: YAG laser as excitation source, the echelle spectrometer and ICCD detector are used for spectral separation and high sensitive detection with high resolution and wide spectral range. The delay time 900ns and gate time 1600ns are determined in the experiment. The calibration curve of Pb is plotted based on the different concentration measurement results, and a limit of detection of 0.0138mg / L is obtained for Pb in water. Graphite conch method effectively overcomes the current problems on laser-induced breakdown spectroscopy detection of heavy metal in water. The detection limits and stability are improved. The reference data is provided for further study on the fast measurement of trace heavy metals in water by laser induced breakdown spectroscopy technique.

  9. Experimental study of the breakdown of cellulose in fast flowing streams

    Energy Technology Data Exchange (ETDEWEB)

    Egglishaw, H.J.

    1972-01-01

    The rate of breakdown of cellulose at three stations on one stream and at stations on five other fast-flowing streams, differing chemically, was investigated by measuring the loss of tensile strength of cotton duch (94% dry weight cellulose). The loss in strength ranged from 95% in 12 weeks to 42% in 40 weeks. The order of stations by rate of breakdown of the cotton was significantly correlated with the order by nitrate concentration of the water. Microscopic examination of the cotton showed that fungi of the polycentric chytrid family cladochytriaceae were the dominant organisms present. Experiments were also carried out on the breakdown of the cotton in a flume and in laboratory tanks.

  10. The inception of pulsed discharges in air: simulations in background fields above and below breakdown

    Science.gov (United States)

    Sun, Anbang; Teunissen, Jannis; Ebert, Ute

    2014-11-01

    We investigate discharge inception in air, in uniform background electric fields above and below the breakdown threshold. We perform 3D particle simulations that include a natural level of background ionization in the form of positive and \\text{O}2- ions. In background fields below breakdown, we use a strongly ionized seed of electrons and positive ions to enhance the field locally. In the region of enhanced field, we observe the growth of positive streamers, as in previous simulations with 2D plasma fluid models. The inclusion of background ionization has little effect in this case. When the background field is above the breakdown threshold, the situation is very different. Electrons can then detach from \\text{O}2- and start ionization avalanches in the whole volume. These avalanches together create one extended discharge, in contrast to the ‘double-headed’ streamers found in many fluid simulations.

  11. Analysis of plutonium oxide surrogate residue using laser-induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    Laser-induced breakdown spectroscopy was used to determine the elemental composition of a CeO2 composite powder for process control verification during lanthanide borosilicate glass fabrication. Cerium oxide is used as a surrogate for plutonium oxide, which along with other canister contents will be combined with frit to make glass. Laser-induced breakdown spectroscopy data for the composition of the CeO2 batch containing concentrations of Ce, Cr, Si, Fe, Ta, Ni, Zn, Al Mg, Gd, and W were quantitatively determined from laser-induced breakdown spectroscopy spectra of both pellet and powder samples. The results of both forms were compared and it was determined that the pellet data gave slightly better precision than the powder sample

  12. Breakdown assisted by a novel electron drift injection in the J-TEXT tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Nengchao; Jin, Hai; Zhuang, Ge, E-mail: ge-zhuang@mail.hust.edu.cn; Ding, Yonghua; Pan, Yuan; Cen, Yishun; Chen, Zhipeng; Huang, Hai; Liu, Dequan; Rao, Bo; Zhang, Ming; Zou, Bichen [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2014-07-15

    A novel electron drift injection (EDI) system aiming to improve breakdown behavior has been designed and constructed on the Joint Texas EXperiment Tokamak Tokamak. Electrons emitted by the system undergo the E×B drift, ∇B drift and curvature drift in sequence in order to traverse the confining magnetic field. A local electrostatic well, generated by a concave-shaped plate biased more negative than the cathode, is introduced to interrupt the emitted electrons moving along the magnetic field line (in the parallel direction) in an attempt to bring an enhancement of the injection efficiency and depth. A series of experiments have demonstrated the feasibility of this method, and a penetration distance deeper than 9.5 cm is achieved. Notable breakdown improvements, including the reduction of breakdown delay and average loop voltage, are observed for discharges assisted by EDI. The lower limit of successfully ionized pressure is expanded.

  13. Breakdown assisted by a novel electron drift injection in the J-TEXT tokamak

    International Nuclear Information System (INIS)

    A novel electron drift injection (EDI) system aiming to improve breakdown behavior has been designed and constructed on the Joint Texas EXperiment Tokamak Tokamak. Electrons emitted by the system undergo the E×B drift, ∇B drift and curvature drift in sequence in order to traverse the confining magnetic field. A local electrostatic well, generated by a concave-shaped plate biased more negative than the cathode, is introduced to interrupt the emitted electrons moving along the magnetic field line (in the parallel direction) in an attempt to bring an enhancement of the injection efficiency and depth. A series of experiments have demonstrated the feasibility of this method, and a penetration distance deeper than 9.5 cm is achieved. Notable breakdown improvements, including the reduction of breakdown delay and average loop voltage, are observed for discharges assisted by EDI. The lower limit of successfully ionized pressure is expanded

  14. Mid-infrared Molecular Emission Studies from Energetic Materials using Laser-Induced Breakdown Spectroscopy

    Science.gov (United States)

    Brown, Ei; Hommerich, Uwe; Yang, Clayton; Trivedi, Sudhir; Samuels, Alan; Snyder, Peter

    2011-10-01

    Laser-induced breakdown spectroscopy (LIBS) is a powerful diagnostic tool for detection of trace elements by monitoring the atomic and ionic emission from laser-induced plasmas. The laser-induced plasma was produced by focusing a 30 mJ pulsed Nd:YAG laser (1064 nm) to dissociate, atomize, and ionize target molecules. In this work, LIBS emissions in the mid-infrared (MIR) region were studied for potential applications in chemical, biological, and explosives (CBE) sensing. We report on the observation of MIR emissions from energetic materials (e.g. ammonium compounds) due to laser-induced breakdown processes. All samples showed LIBS-triggered oxygenated breakdown products as well as partially dissociated and recombination molecular species. More detailed results of the performed MIR LIBS studies on the energetic materials will be discussed at the conference.

  15. Effect of Doppler-shifted photons on subnanosecond breakdown in high-voltage pulse discharge

    Science.gov (United States)

    Schweigert, I. V.; Alexandrov, A. L.; Zakrevsky, Dm. E.; Bokhan, P. A.

    2016-06-01

    The experiments in high-voltage open discharge in helium [1, 2] showed a controlled current growth rate of 500 A/(cm2ns) for an applied voltage of 20 kV and gas pressure of 6 Torr. A kinetic model of the subnanosecond breakdown is developed to analyze the mechanism of current growth, which takes into account the kinetics of electrons, ions, fast atoms and photons with a Doppler shift (DS). DS photons appear in discharge due to collisions of heavy particles. Using particle in cell simulations, we show a critical role of DS photons in the electron emission from the cathode during the breakdown. Our experimental and calculation results show a decrease of the breakdown time with increasing gas pressure from 3 Torr to 16 Torr.

  16. Shifts in leaf litter breakdown along a forest-pasture-urban gradient in Andean streams.

    Science.gov (United States)

    Iñiguez-Armijos, Carlos; Rausche, Sirkka; Cueva, Augusta; Sánchez-Rodríguez, Aminael; Espinosa, Carlos; Breuer, Lutz

    2016-07-01

    Tropical montane ecosystems of the Andes are critically threatened by a rapid land-use change which can potentially affect stream variables, aquatic communities, and ecosystem processes such as leaf litter breakdown. However, these effects have not been sufficiently investigated in the Andean region and at high altitude locations in general. Here, we studied the influence of land use (forest-pasture-urban) on stream physico-chemical variables (e.g., water temperature, nutrient concentration, and pH), aquatic communities (macroinvertebrates and aquatic fungi) and leaf litter breakdown rates in Andean streams (southern Ecuador), and how variation in those stream physico-chemical variables affect macroinvertebrates and fungi related to leaf litter breakdown. We found that pH, water temperature, and nutrient concentration increased along the land-use gradient. Macroinvertebrate communities were significantly different between land uses. Shredder richness and abundance were lower in pasture than forest sites and totally absent in urban sites, and fungal richness and biomass were higher in forest sites than in pasture and urban sites. Leaf litter breakdown rates became slower as riparian land use changed from natural to anthropogenically disturbed conditions and were largely determined by pH, water temperature, phosphate concentration, fungal activity, and single species of leaf-shredding invertebrates. Our findings provide evidence that leaf litter breakdown in Andean streams is sensitive to riparian land-use change, with urban streams being the most affected. In addition, this study highlights the role of fungal biomass and shredder species (Phylloicus; Trichoptera and Anchytarsus; Coleoptera) on leaf litter breakdown in Andean streams and the contribution of aquatic fungi in supporting this ecosystem process when shredders are absent or present low abundance in streams affected by urbanization. Finally, we summarize important implications in terms of managing of

  17. X-Band Photonic Band-Gap Accelerator Structure Breakdown Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Marsh, Roark A.; /MIT /MIT /NIFS, Gifu /JAERI, Kyoto /LLNL, Livermore; Shapiro, Michael A.; Temkin, Richard J.; /MIT; Dolgashev, Valery A.; Laurent, Lisa L.; Lewandowski, James R.; Yeremian, A.Dian; Tantawi, Sami G.; /SLAC

    2012-06-11

    In order to understand the performance of photonic band-gap (PBG) structures under realistic high gradient, high power, high repetition rate operation, a PBG accelerator structure was designed and tested at X band (11.424 GHz). The structure consisted of a single test cell with matching cells before and after the structure. The design followed principles previously established in testing a series of conventional pillbox structures. The PBG structure was tested at an accelerating gradient of 65 MV/m yielding a breakdown rate of two breakdowns per hour at 60 Hz. An accelerating gradient above 110 MV/m was demonstrated at a higher breakdown rate. Significant pulsed heating occurred on the surface of the inner rods of the PBG structure, with a temperature rise of 85 K estimated when operating in 100 ns pulses at a gradient of 100 MV/m and a surface magnetic field of 890 kA/m. A temperature rise of up to 250 K was estimated for some shots. The iris surfaces, the location of peak electric field, surprisingly had no damage, but the inner rods, the location of the peak magnetic fields and a large temperature rise, had significant damage. Breakdown in accelerator structures is generally understood in terms of electric field effects. These PBG structure results highlight the unexpected role of magnetic fields in breakdown. The hypothesis is presented that the moderate level electric field on the inner rods, about 14 MV/m, is enhanced at small tips and projections caused by pulsed heating, leading to breakdown. Future PBG structures should be built to minimize pulsed surface heating and temperature rise.

  18. Microcontroller based system for electrical breakdown time delay measurement in gas-filled devices

    International Nuclear Information System (INIS)

    This paper presents realization of a digital embedded system for measuring electrical breakdown time delay. The proposed system consists of three major parts: dc voltage supply, analog subsystem, and a digital subsystem. Any dc power source with the range from 100 to 1000 V can be used in this application. The analog subsystem should provide fast and accurate voltage switching on the testing device as well as transform the signals that represent the voltage pulse on the device and the device breakdown into the form suitable for detection by a digital subsystem. The insulated gate bipolar transistor IRG4PH40KD driven by TC429 MOSFET driver is used for high voltage switching on the device. The aim of a digital subsystem is to detect the signals from the analog subsystem and to measure the elapsed time between their occurrences. Moreover, the digital subsystem controls various parameters that influence time delay and provides fast data storage for a large number of measured data. For this propose, we used the PIC18F4550 microcontroller with a full-speed compatible universal serial bus (USB) engine. Operation of this system is verified on different commercial and custom made gas devices with different structure and breakdown mechanisms. The electrical breakdown time delay measurements have been carried out as a function of several parameters, which dominantly influence electrical breakdown time delay. The obtained results have been verified using statistical methods, and they show good agreement with the theory. The proposed system shows good repeatability, sensitivity, and stability for measuring the electrical breakdown time delay.

  19. Microcontroller based system for electrical breakdown time delay measurement in gas-filled devices

    Science.gov (United States)

    Pejović, Milić M.; Denić, Dragan B.; Pejović, Momčilo M.; Nešić, Nikola T.; Vasović, Nikola

    2010-10-01

    This paper presents realization of a digital embedded system for measuring electrical breakdown time delay. The proposed system consists of three major parts: dc voltage supply, analog subsystem, and a digital subsystem. Any dc power source with the range from 100 to 1000 V can be used in this application. The analog subsystem should provide fast and accurate voltage switching on the testing device as well as transform the signals that represent the voltage pulse on the device and the device breakdown into the form suitable for detection by a digital subsystem. The insulated gate bipolar transistor IRG4PH40KD driven by TC429 MOSFET driver is used for high voltage switching on the device. The aim of a digital subsystem is to detect the signals from the analog subsystem and to measure the elapsed time between their occurrences. Moreover, the digital subsystem controls various parameters that influence time delay and provides fast data storage for a large number of measured data. For this propose, we used the PIC18F4550 microcontroller with a full-speed compatible universal serial bus (USB) engine. Operation of this system is verified on different commercial and custom made gas devices with different structure and breakdown mechanisms. The electrical breakdown time delay measurements have been carried out as a function of several parameters, which dominantly influence electrical breakdown time delay. The obtained results have been verified using statistical methods, and they show good agreement with the theory. The proposed system shows good repeatability, sensitivity, and stability for measuring the electrical breakdown time delay.

  20. Some problems on rf breakdown in room temperature accelerator structure, a possible criterion

    International Nuclear Information System (INIS)

    The discussion is confined to high gradient, room-temperature accelerators which have clean well-finished cavity surfaces and good vacuum conditions. Breakdown-initiating mechanisms due to ''cold'' field electron emission occurring at isolated sites on broad-area cavity surfaces, where the field is enhanced, are described. The influences of an alternating field and transition time tunneling are taken into account. The thermal instability resulting in vacuum voltage breakdown is hypothesized to derive a new criterion for room-temperature accelerator structure. 18 refs., 5 figs

  1. On the dynamics of a subnanosecond breakdown in nitrogen below atmospheric pressures

    International Nuclear Information System (INIS)

    The dynamics of a breakdown in a gas-filled diode with a highly inhomogeneous electric field was studied in experiments at a time resolution of ∼100 ps and in numerical simulation by the 2D axisymmetric particle-in-cell (PIC) code XOOPIC. The diode was filled with nitrogen at pressures of up to 100 Torr. The dynamics of the electric field distribution in the diode during the breakdown was analyzed, and the factors that limit the pulse duration of the runaway electron beam current at different pressures were determined

  2. Time-dependent dielectric breakdown measurements of porous organosilicate glass using mercury and solid metal probes

    International Nuclear Information System (INIS)

    Time-dependent dielectric breakdown (TDDB) is one of the major concerns for low-k dielectric materials. During plasma processing, low-k dielectrics are subjected to vacuum ultraviolet photon radiation and charged-particle bombardment. To examine the change of TDDB properties, time-to-breakdown measurements are made to porous SiCOH before and after plasma exposure. Significant discrepancies between mercury and solid-metal probes are observed and have been shown to be attributed to mercury diffusion into the dielectric porosities

  3. On the dynamics of a subnanosecond breakdown in nitrogen below atmospheric pressures

    Energy Technology Data Exchange (ETDEWEB)

    Shklyaev, V. A., E-mail: shklyaev@to.hcei.tsc.ru, E-mail: beh@loi.hcei.tsc.ru [Laboratory of Theoretical Physics, Institute of High Current Electronics, Russian Academy of Sciences, 2/3 Akademichesky Ave., 634055 Tomsk (Russian Federation); Institute of High Technology Physics, National Research Tomsk Polytechnic University, 30 Lenin Avenue, 634050 Tomsk (Russian Federation); Baksht, E. Kh., E-mail: shklyaev@to.hcei.tsc.ru, E-mail: beh@loi.hcei.tsc.ru; Tarasenko, V. F. [Laboratory of Optical Radiations, Institute of High Current Electronics, Russian Academy of Sciences, 2/3 Akademichesky Ave., 634055 Tomsk (Russian Federation); Belomyttsev, S. Ya.; Grishkov, A. A. [Laboratory of Theoretical Physics, Institute of High Current Electronics, Russian Academy of Sciences, 2/3 Akademichesky Ave., 634055 Tomsk (Russian Federation); Burachenko, A. G. [Laboratory of Optical Radiations, Institute of High Current Electronics, Russian Academy of Sciences, 2/3 Akademichesky Ave., 634055 Tomsk (Russian Federation); Laboratory of Low Temperature Plasma, Tomsk State University, 36 Lenin Ave., 634050 Tomsk (Russian Federation)

    2015-12-07

    The dynamics of a breakdown in a gas-filled diode with a highly inhomogeneous electric field was studied in experiments at a time resolution of ∼100 ps and in numerical simulation by the 2D axisymmetric particle-in-cell (PIC) code XOOPIC. The diode was filled with nitrogen at pressures of up to 100 Torr. The dynamics of the electric field distribution in the diode during the breakdown was analyzed, and the factors that limit the pulse duration of the runaway electron beam current at different pressures were determined.

  4. Breakdown voltage in vertical power FLIMOSFETs with one internal floating island

    Science.gov (United States)

    Galadi, A.; Morancho, F.; Hassani, M. M.

    2008-09-01

    Recently a new power FLIMOSFET ('floating islands MOSFET') structure was proposed to reduce conduction losses in power MOS devices. The vertical FLIMOSFET offers a better trade-off between breakdown voltage and specific on-resistance compared to the conventional VDMOSFET. The improvement of this trade-off was obtained by inserting one (or several) floating island(s) in the epitaxial layer of the VDMOS transistor. In this paper, theoretical analysis of breakdown voltage of the FLIMOSFET with a single floating island is proposed. This analytical method exhibits good agreement with 2D simulations and measurements.

  5. Breakdown voltage in vertical power FLIMOSFETs with one internal floating island

    International Nuclear Information System (INIS)

    Recently a new power FLIMOSFET ('floating islands MOSFET') structure was proposed to reduce conduction losses in power MOS devices. The vertical FLIMOSFET offers a better trade-off between breakdown voltage and specific on-resistance compared to the conventional VDMOSFET. The improvement of this trade-off was obtained by inserting one (or several) floating island(s) in the epitaxial layer of the VDMOS transistor. In this paper, theoretical analysis of breakdown voltage of the FLIMOSFET with a single floating island is proposed. This analytical method exhibits good agreement with 2D simulations and measurements

  6. Effects of rf breakdown on the beam in the Compact Linear Collider prototype accelerator structure

    OpenAIRE

    Palaia, Andrea; Jacewicz, Marek; Ruber, Roger; Ziemann, Volker; Farabolini, Wilfrid

    2013-01-01

    Understanding the effects of rf breakdown in high-gradient accelerator structures on the acceleratedbeam is an extremely relevant aspect in the development of the Compact Linear Collider (CLIC) andis one of the main issues addressed at the Two-beam Test Stand at the CLIC Test Facility 3 at CERN.During a rf breakdown high currents are generated causing parasitic magnetic fields that interact withthe accelerated beam affecting its orbit. The beam energy is also affected because the power is part...

  7. Experimental Investigation of the Relationship between Breakdown Strength and Tracking Characteristics of Composites

    DEFF Research Database (Denmark)

    Madsen, Søren Find; Holbøll, Joachim; Henriksen, Mogens;

    2005-01-01

    The following paper shows possible correlations between results obtained by tracking tests and breakdown field strengths for non coated Glass Fibre Reinforced Polymers (GFRP) with either a polyester or an epoxy based resin. 15 specimens have been tested according to IEC Publication 60587 [4]. The...... breakdown field strength of specimens cut from similar samples is then determined by a new method capable of estimating the stressed volume [8]. The two values are finally compared and sought incorporated in an analytical formula. All test specimens are supplied by Danish manufacturers of wind turbine...

  8. Elemental analysis of halogens using molecular emission by laser-induced breakdown spectroscopy in air

    International Nuclear Information System (INIS)

    Fluorine and chlorine do not produce atomic and ionic line spectra of sufficient intensity to permit their detection by laser-induced breakdown spectroscopy. They do, however, combine with alkali-earths and other elements to form molecules whose spectra may be easily identified, enabling detection in ambient conditions with much higher sensitivity than using F I and Cl I atomic lines. - Highlights: • We studied laser induced breakdown spectra of halogens with alkali-earth elements. • Emission and temporal behavior of CaF and CaCl molecules were determined. • Sensitivity of F and Cl detection by molecules and atoms was compared

  9. Mass spectrometric studies of the electrical breakdown of thin polymer films

    Science.gov (United States)

    Kendall, B. R. F.; Rohrer, V. S.; Bojan, V. J.

    1986-01-01

    The composition of the neutral particles released during the electrical breakdown of 50-micron and 75-micron insulating films of the type used on spacecraft exteriors investigated experimentally using a time-of-flight mass spectrometer triggered by the breakdown event. The experimental apparatus is described in detail, and the results are presented in photographs. It is found that the particle flux from Teflon FEP and PFA films comprise mainly fluorocarbon fragments, some with mass 350 amu or greater, but the flux from Kapton oxygen-ion-beam treated Kapton, Tefzel, and Mylar comprises mainly molecules of mass 44 amu or less.

  10. Investigation of environmentally relevant colloids by laser-induced breakdown detection (LIBD)

    International Nuclear Information System (INIS)

    Full text of publication follows: An apparatus for laser-induced breakdown detection (LIBD) was established, which is aimed at in-situ detection of aquatic colloids of a particle size down to 2 atmosphere) by cathodic reduction of uranium(VI) followed by the successive increase of the pH by coulometric titration. The formation of these colloids was traced by LIBD. [1] Walther, C., Bitea, C., Hauser, W., Kim, J.I. and Scherbaum, F.J. Laser Induced Breakdown Detection for the Assessment of Colloid Mediated Radionuclide Migration. Nucl. Instr. and Meth. B 195 (2002) 374-388. (authors)

  11. Transistor collector breakdown in the presence of conducted EMP and gamma radiation

    International Nuclear Information System (INIS)

    In this paper we develop expressions which describe breakdown, negative resistance and latch characteristics for a common emitter transistor when exposed to simultaneous conducted EMP and ionizing radiation. These expressions are derived from a modified Ebers-Moll model and show that common emitter breakdown voltage is reduced, latch (or sustaining voltage) remains unchanged, and that the negative resistance characteristics are changed. Using the modified Ebers-Moll model good agreement between predicted and observed circuit response is demonstrated when the circuits are exposed to a rising collector voltage (due to EMP) and simultaneous ionizing (gamma) radiation

  12. Breakdown transient study of plasma distributions in a 2.45 GHz hydrogen discharge

    Energy Technology Data Exchange (ETDEWEB)

    Cortázar, O.D., E-mail: daniel.cortazar@uclm.es [Universidad de Castilla-La Mancha, ETSII-INEI, Applied Mechanics and Projects Department, C.J. Cela s/n, 13170 Ciudad Real (Spain); Megía-Macías, A. [ESS Bilbao Consortium, Polígono Ugaldeguren-III Pol. A 7B, 48170-Zamudio, Vizcaya (Spain); Tarvainen, O.; Koivisto, H. [University of Jyväskylä, Department of Physics, PO Box 35 (YFL), 40500 Jyväskylä (Finland)

    2015-05-01

    Plasma distribution transients associated with the breakdown of a 2.45 GHz hydrogen discharge similar to high current microwave ion sources are studied by means of an ultra-fast frame image acquisition system in visible light range. Eight different plasma distributions have been studied by photographing the 2D projections of the discharge through a transparent plasma electrode. The temporal evolution of images in Balmer-alpha and Fulcher band wavelengths have been recorded associated to atomic and molecular excitation and ionization processes. Some unexpected plasma distributions transient behaviors during breakdown are reported.

  13. Elemental analysis of halogens using molecular emission by laser-induced breakdown spectroscopy in air

    Energy Technology Data Exchange (ETDEWEB)

    Gaft, M.; Nagli, L.; Eliezer, N.; Groisman, Y. [Laser Distance Spectrometry, 9 Mota Gur St., Petah Tikva 49514 (Israel); Forni, O. [Université de Toulouse, UPS-OMP, IRAP, Toulouse (France); CNRS, IRAP, 9 Av. Colonel Roche, BP 44346, F-31028 Toulouse cedex 4 (France)

    2014-08-01

    Fluorine and chlorine do not produce atomic and ionic line spectra of sufficient intensity to permit their detection by laser-induced breakdown spectroscopy. They do, however, combine with alkali-earths and other elements to form molecules whose spectra may be easily identified, enabling detection in ambient conditions with much higher sensitivity than using F I and Cl I atomic lines. - Highlights: • We studied laser induced breakdown spectra of halogens with alkali-earth elements. • Emission and temporal behavior of CaF and CaCl molecules were determined. • Sensitivity of F and Cl detection by molecules and atoms was compared.

  14. Off-state avalanche breakdown induced degradation in 20 V NLDMOS devices

    International Nuclear Information System (INIS)

    Degradation behaviors of 20 V NLDMOS operated under off-state avalanche breakdown conditions are presented. A constant current pulse stressing test is applied to the device. Two different degradation mechanisms are identified by analysis of electrical data, technology computer-aided design (TCAD) simulations and charge pumping measurements. The first mechanism is attributed to positive oxide-trapped charges in the N-type drift region, and the second one is due to decreased electron mobility upon interface state formation in the drift region. Both of the mechanisms are enhanced with increasing avalanche breakdown current. (semiconductor devices)

  15. Breakdown characteristics in pulsed-driven dielectric barrier discharges: influence of the pre-breakdown phase due to volume memory effects

    International Nuclear Information System (INIS)

    The pre-phase of the breakdown of pulsed-driven dielectric barrier discharges (DBDs) was investigated by fast optical and electrical measurements on double-sided DBDs with a 1 mm gap in a gas mixture of 0.1 vol% O2 in N2 at atmospheric pressure. Depending on the pulse width (the pause time between subsequent DBDs), four different breakdown regimes of the following discharge were observed. By systematically reducing the pulse width, the breakdown characteristics could be changed from a single cathode-directed propagation (positive streamer) to simultaneous cathode- and anode-directed propagations (positive and negative streamer) and no propagation at all for sub-μs pulse times. For all cases, different spatio-temporal emission structures in the pre-phase were observed. The experimental results were compared with time-dependent, spatially one-dimensional fluid model calculations. The modelling results confirmed that different pre-ionisation conditions, i.e. considerably high space charges in the volume created by the residual electrons and ions from the previous discharge, are the reason for the observed phenomena. (paper)

  16. Breakdown characteristics in pulsed-driven dielectric barrier discharges: influence of the pre-breakdown phase due to volume memory effects

    Science.gov (United States)

    Höft, H.; Kettlitz, M.; Becker, M. M.; Hoder, T.; Loffhagen, D.; Brandenburg, R.; Weltmann, K.-D.

    2014-11-01

    The pre-phase of the breakdown of pulsed-driven dielectric barrier discharges (DBDs) was investigated by fast optical and electrical measurements on double-sided DBDs with a 1 mm gap in a gas mixture of 0.1 vol% O2 in N2 at atmospheric pressure. Depending on the pulse width (the pause time between subsequent DBDs), four different breakdown regimes of the following discharge were observed. By systematically reducing the pulse width, the breakdown characteristics could be changed from a single cathode-directed propagation (positive streamer) to simultaneous cathode- and anode-directed propagations (positive and negative streamer) and no propagation at all for sub-μs pulse times. For all cases, different spatio-temporal emission structures in the pre-phase were observed. The experimental results were compared with time-dependent, spatially one-dimensional fluid model calculations. The modelling results confirmed that different pre-ionisation conditions, i.e. considerably high space charges in the volume created by the residual electrons and ions from the previous discharge, are the reason for the observed phenomena.

  17. 7 CFR Exhibit A to Subpart A of... - Estimated Breakdown of Dwelling Costs for Estimating Partial Payments

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 12 2010-01-01 2010-01-01 false Estimated Breakdown of Dwelling Costs for Estimating Partial Payments A Exhibit A to Subpart A of Part 1924 Agriculture Regulations of the Department of... A of Part 1924—Estimated Breakdown of Dwelling Costs for Estimating Partial Payments With slab...

  18. Computational studies of suppression of microwave gas breakdown by crossed dc magnetic field using electron fluid model

    Science.gov (United States)

    Zhao, Pengcheng; Guo, Lixin; Shu, Panpan

    2016-08-01

    The gas breakdown induced by a square microwave pulse with a crossed dc magnetic field is investigated using the electron fluid model, in which the accurate electron energy distribution functions are adopted. Simulation results show that at low gas pressures the dc magnetic field of a few tenths of a tesla can prolong the breakdown formation time by reducing the mean electron energy. With the gas pressure increasing, the higher dc magnetic field is required to suppress the microwave breakdown. The electric field along the microwave propagation direction generated due to the motion of electrons obviously increases with the dc magnetic field, but it is much less than the incident electric field. The breakdown predictions of the electron fluid model agree very well with the particle-in-cell-Monte Carlo collision simulations as well as the scaling law for the microwave gas breakdown.

  19. Study on the lightning impulse breakdown characteristics of gaseous insulation media for the design of a high voltage superconducting apparatus

    International Nuclear Information System (INIS)

    In general, the current leads of high voltage superconducting apparatuses cooled by liquid nitrogen are exposed to gaseous insulation media. Therefore, the investigation on the electrical breakdown characteristics of gaseous insulation media should be performed to develop electrically reliable high voltage superconducting power apparatuses. In this study, the lightning impulse breakdown tests on gaseous insulation media are conducted by using sphere-to-plane electrode systems made of stainless steel. Also, the lightning impulse breakdown voltage tests on gaseous insulation media according to various pressures are performed. The experimental results show that the electrical breakdown characteristics under lightning impulse voltage are affected by the gap length between electrode systems, the size of electrodes, and the field utilization factors. From these results, the electrical insulation design criteria to estimate the electrical breakdown voltage are established. The results are expected to be applicable to the design of current leads for high voltage superconducting apparatuses.

  20. Conjecture of perturbative QED breakdown at $\\alpha\\chi^{2/3} \\gtrsim 1$

    CERN Document Server

    Fedotov, A M

    2016-01-01

    Invited talk given at Symposium "Extreme Light Technologies, Science, and Applications" (LPHYS'16, Yerevan, 11-15 July 2016). The old Ritus-Narozhny conjecture of possible breakdown of Intense Field QED perturbation theory for ultrarelativistic particles passing transversely through a strong electromagnetic field is reviewed with a special emphasis on its possible significance for near-future experiments.

  1. High Temperature Characteristic in Electrical Breakdown and Electrical Conduction of Epoxy/Boron-nitride Composite

    Science.gov (United States)

    Takenaka, Yutaka; Kurimoto, Muneaki; Murakami, Yoshinobu; Nagao, Masayuki

    The power module for the electrical vehicle needs electrical insulation material with high thermal conductivity. Recently, the epoxy insulating material filled with boron-nitride particles (epoxy/boron-nitride composite) is focused as an effective solution. However, the insulation performance of epoxy/boron-nitride composite was not investigated enough especially at the high temperature in which the power module was used, i.e. more than 100°C. In this paper, we investigated high temperature characteristics in electrical breakdown and conduction current of epoxy/boron-nitride composite. Breakdown test under the application of DC lamp voltage and impulse voltage clarified that the epoxy/boron-nitride composite had the constant breakdown strength even in the high temperature. Comparison of the epoxy/boron-nitride composite with previous material, which was epoxy/alumina composite, indicated that the breakdown voltage of the epoxy/boron-nitride composite in the high temperature was found to be higher than that of epoxy/alumina composite under the same thermal-transfer quantity among them. Furthermore, conduction current measurement of epoxy/boron-nitride composite in the high temperature suggested the possibility of the ionic conduction mechanism.

  2. 39GHz ECRH system for breakdown studies on the TCA tokamak

    International Nuclear Information System (INIS)

    The design construction and first operation of a 39GHz ECRH system (300 kW, 100 ms) for low loop-voltage breakdown and startup-assist experiments on the TCA tokamak is described. (author) 5 refs., 6 figs., 1 tab

  3. A one-dimensional study of the evolution of the microwave breakdown in air

    International Nuclear Information System (INIS)

    The microwave breakdown in air is simulated numerically within a simple 1D model taking into account a perturbation of electromagnetic field by plasma. The simulations were performed using two qualitatively different codes. One of these codes is based on computation of Maxwell equations, whereas the other one utilizes an approximation of quasi-monochromatic electromagnetic field. There is a good agreement between simulation results obtained by using both codes. Calculations have been carried out in a wide range of air pressures and field frequencies; also varied were initial spatial distributions of plasma density. The results reveal strong dependence of the breakdown evolution on the relation between the field frequency and the gas pressure as well as on the presence of extended rarefied background plasma. At relatively low gas pressures (or high field frequencies), the breakdown process is accompanied by the stationary ionization wave propagating towards the incident electromagnetic wave. In the case of a high gas pressure (or a relatively low field frequency), the peculiarities of the breakdown are associated with a formation of plasma filament array. The extended background plasma can suppress formation of the plasma filament array completely even at high pressures (or low frequencies)

  4. Catabolism of circulating enzymes: plasma clearance, endocytosis, and breakdown of lactate dehydrogenase-1 in rabbits

    Energy Technology Data Exchange (ETDEWEB)

    Smit, M.J.; Beekhuis, H.; Duursma, A.M.; Bouma, J.M.; Gruber, M.

    1988-12-01

    Lactate dehydrogenase-1, intravenously injected into rabbits, was cleared with first-order kinetics (half-life 27 min), until at least 80% of the injected activity had disappeared from plasma. Radioactivity from injected SVI-labeled enzyme disappeared at this same rate. Trichloroacetic-acid-soluble breakdown products started to appear in the circulation shortly after injection of the labeled enzyme. Body scans of the rabbits for 80 min after injection of T I-labeled enzyme revealed rapid accumulation of label in the liver, peaking 10-20 min after injection. Subsequently, activity in the liver declined and radioactivity (probably labeled breakdown products of low molecular mass) steadily accumulated in the bladder. Tissue fractionation of liver, 19 min after injection of labeled enzyme, indicated that the radioactivity was present both in endosomes and in lysosomes, suggesting uptake by endocytosis, followed by breakdown in the lysosomes. Measurements of radioactivity in liver and plasma suggest that the liver is responsible for the breakdown of at least 75% of the injected enzyme. Radioautography of tissue sections of liver and spleen showed accumulated radioactivity in sinusoidal liver cells and red pulpa, respectively. These results are very similar to those for lactate dehydrogenase-5, creatine kinase MM, and several other enzymes that we have previously studied in rats.

  5. Catabolism of circulating enzymes: plasma clearance, endocytosis, and breakdown of lactate dehydrogenase-1 in rabbits.

    Science.gov (United States)

    Smit, M J; Beekhuis, H; Duursma, A M; Bouma, J M; Gruber, M

    1988-12-01

    Lactate dehydrogenase-1 (EC 1.1.1.27), intravenously injected into rabbits, was cleared with first-order kinetics (half-life 27 min), until at least 80% of the injected activity had disappeared from plasma. Radioactivity from injected 125I-labeled enzyme disappeared at this same rate. Trichloroacetic-acid-soluble breakdown products started to appear in the circulation shortly after injection of the labeled enzyme. Body scans of the rabbits for 80 min after injection of 131I-labeled enzyme revealed rapid accumulation of label in the liver, peaking 10-20 min after injection. Subsequently, activity in the liver declined and radioactivity (probably labeled breakdown products of low molecular mass) steadily accumulated in the bladder. Tissue fractionation of liver, 19 min after injection of labeled enzyme, indicated that the radioactivity was present both in endosomes and in lysosomes, suggesting uptake by endocytosis, followed by breakdown in the lysosomes. Measurements of radioactivity in liver and plasma suggest that the liver is responsible for the breakdown of at least 75% of the injected enzyme. Radioautography of tissue sections of liver and spleen showed accumulated radioactivity in sinusoidal liver cells and red pulpa, respectively. These results are very similar to those for lactate dehydrogenase-5, creatine kinase MM, and several other enzymes that we have previously studied in rats. PMID:3197286

  6. Catabolism of circulating enzymes: plasma clearance, endocytosis, and breakdown of lactate dehydrogenase-1 in rabbits

    International Nuclear Information System (INIS)

    Lactate dehydrogenase-1, intravenously injected into rabbits, was cleared with first-order kinetics (half-life 27 min), until at least 80% of the injected activity had disappeared from plasma. Radioactivity from injected 125I-labeled enzyme disappeared at this same rate. Trichloroacetic-acid-soluble breakdown products started to appear in the circulation shortly after injection of the labeled enzyme. Body scans of the rabbits for 80 min after injection of 131I-labeled enzyme revealed rapid accumulation of label in the liver, peaking 10-20 min after injection. Subsequently, activity in the liver declined and radioactivity (probably labeled breakdown products of low molecular mass) steadily accumulated in the bladder. Tissue fractionation of liver, 19 min after injection of labeled enzyme, indicated that the radioactivity was present both in endosomes and in lysosomes, suggesting uptake by endocytosis, followed by breakdown in the lysosomes. Measurements of radioactivity in liver and plasma suggest that the liver is responsible for the breakdown of at least 75% of the injected enzyme. Radioautography of tissue sections of liver and spleen showed accumulated radioactivity in sinusoidal liver cells and red pulpa, respectively. These results are very similar to those for lactate dehydrogenase-5, creatine kinase MM, and several other enzymes that we have previously studied in rats

  7. Nanoparticle detection in aqueous solutions using Raman and Laser Induced Breakdown Spectroscopy

    NARCIS (Netherlands)

    Sovago, M.; Buis, E.-J.; Sandtke, M.

    2013-01-01

    We show the chemical identification and quantification of the concentration and size of nanoparticle (NP) dispersions in aqueous solutions by using a combination of Raman Spectroscopy and Laser Induced Breakdown Spectroscopy (LIBS). The two spectroscopic techniques are applied to demonstrate the NP

  8. Dielectric breakdown strength of magnetic nanofluid based on insulation oil after impulse test

    Science.gov (United States)

    Nazari, M.; Rasoulifard, M. H.; Hosseini, H.

    2016-02-01

    In this study, the dielectric breakdown strength of magnetic nanofluids based on transformer mineral oil for use in power systems is reviewed. Nano oil samples are obtained from dispersion of the magnetic nanofluid within uninhibited transformer mineral oil NYTRO LIBRA as the base fluid. AC dielectric breakdown voltage measurement was carried out according to IEC 60156 standard and the lightning impulse breakdown voltage was obtained by using the sphere-sphere electrodes in an experimental setup for nano oil in volume concentration of 0.1-0.6%. Results indicate improved AC and lightning impulse breakdown voltage of nano oil compared to the base oil. AC test was performed again after applying impulse current and result showed that nano oil unlike the base oil retains its dielectric properties. Increase the dielectric strength of the nano oil is mainly due to dielectric and magnetic properties of Fe3O4 nanoparticles that act as free electrons snapper, and reduce the rate of free electrons in the ionization process.

  9. Chiral symmetry breakdown and the spectrum of pseudoscalar mesons in quantum chromodynamics

    International Nuclear Information System (INIS)

    The recently suggested mechanism of the dynamical chiral symmetry breakdown in quantum chromodynamics is extended to the realistic situation when both spontaneous and explicit chiral symmetry breaking take place (current masses of the light quarks are different from zero). The mass relations for pseudoscalar nonet are obtained

  10. Experimental and theoretical studies of near-breakdown phenomena in GaAs-based heterostructure FETs

    OpenAIRE

    Sleiman, A.; Rossi, L.; Di Carlo, A.; Tocca, L.; Bonfiglio, A.; Brunori, M.; Lugli, P.; G. Zandler; Meneghesso, G.; Zanoni, E.; Canali, C.; Cetronio, A.; Lanzieri, M.; Peroni, M

    1999-01-01

    We have investigated electrical and optical phenomena related to impact ionization in the near breakdown regime of heterostruc­ture FETs. The experimental analysis is based on electroluminescence spectroscopy correlated to minority carrier gate current measurements. Such experiments are inter­preted by means of Monte Carlo simulations.

  11. Schlieren photography of current filaments in surface-related breakdown of silicon

    Energy Technology Data Exchange (ETDEWEB)

    Hankla, B.J.; Williams, P.F. [Univ. of Nebraska, Lincoln, NE (United States). Dept. of Electrical Engineering

    1996-02-01

    The authors have used a modified Schlieren technique to photograph current filaments formed inside silicon during the very early stages of surface-related breakdown. They believe that the features they see are due to heating in the filamentary channel. The very rapid formation of these channels suggests that they result from streamer-like phenomena in the bulk silicon.

  12. Empirical Features of Spontaneous and Induced Traffic Breakdowns in Free Flow at Highway Bottlenecks

    CERN Document Server

    Kerner, Boris S; Klenov, Sergey L; Rehborn, Hubert; Leibel, Michael

    2015-01-01

    Based on an empirical study of real field traffic data measured in 1996--2014 through road detectors installed on German freeways, we reveal physical features of empirical nuclei for spontaneous traffic breakdown in free flow at highway bottlenecks. It is shown that the source of a nucleus for traffic breakdown is the solely difference between empirical spontaneous and induced traffic breakdowns at a highway bottleneck. Microscopic traffic simulations with a stochastic traffic flow model in the framework of three-phase theory explain the empirical findings. It turns out that in the most cases, a nucleus for empirical spontaneous traffic breakdown occurs through an interaction of one of waves in free flow with an empirical permanent speed disturbance localized at a highway bottleneck. The wave is a localized structure in free flow, in which the total flow rate is larger and the speed averaged across the highway is smaller than outside the wave. The waves in free flow appear due to oscilations in the percentage...

  13. Bifurcation of Vortex Breakdown Patterns in a Circular Cylinder with two Rotating Covers

    DEFF Research Database (Denmark)

    Brøns, Morten; Bisgaard, Anders

    2006-01-01

    We analyse the topology of vortex breakdown in a closed cylindrical container in the steady domain under variation of three parameters, the aspect ratio of the cylinder, the Reynolds number, and the ratio of the angular velocities of the covers. We develop a general post-processing method to obtain...

  14. Aspergillus Niger reduces skeletal muscle protein breakdown and stimulates growth in broilers

    Directory of Open Access Journals (Sweden)

    Ahmed. A. Saleh

    2011-04-01

    Full Text Available This study was conducted to show that the inclusion of a fungus, Aspergillus Niger, as a dietary supplement in feed reduces protein breakdown in skeletal muscle and stimulates growth in broiler chickens. A total of 24 chicks at 15 d of age were divided into a control group and 3 treatment groups (6 birds per treatment. The control group was fed a basic diet, and the 3 treatment groups were fed the basic diet supplemented with A. Niger at a concentration of 0.01, 0.05 and 0.1% respectively. The birds were raised for 12 d from 15 d of age and were evaluated for the fungi’s effects on growth, organ weight and plasma 3-methylhistidine concentration as an index of skeletal muscle protein breakdown The mRNAs of atrogin-1, ubiquitin, proteasome and m-calpain were also measured to identify the mechanism underlying the decrement of the muscle protein breakdown resulting from Aspergillus. Body weight gain and breast muscle weight were increased even though feed intake by the chicks was decreased by the presence of the fungus, thus improving feed efficiency. Furthermore, plasma 3-methylhistidine concentration was decreased by the fungus. The mRNAs of atrogin-1, ubiquitin, proteasome and m-calpain were decreased, supporting the conclusion that the fungus decreases skeletal muscle protein breakdown. In conclusion, feeding A. Niger improves growth performance because proteolytic activity in skeletal muscle is reduced.

  15. On the electrical breakdown of gaseous dielectrics-an engineering approach

    DEFF Research Database (Denmark)

    Pedersen, Aage

    1989-01-01

    Quantitative criteria are derived for the onset of breakdown in atmospheric air and similar weakly electronegative gases. A comparable criterion is then formulated for strongly electronegative gases such as SF6. These criteria contain no quantities other than those which can be obtained directly...

  16. Identification of the breakdown and analysis of transformer 22/0.4 kV

    OpenAIRE

    Martin Brandt; Dagmar Faktorová; Róbert Seewald

    2013-01-01

    The paper deals with the identification of the breakdown of the transformer withdrawn from operation because of repeated reaction of transformer protections. Successively the transformer was put of operation, removed from the distribution and put to diagnostic measurements. The analysis SFRA contributed to the interturn short circuit.

  17. Identification of the breakdown and analysis of transformer 22/0.4 kV

    Directory of Open Access Journals (Sweden)

    Martin Brandt

    2013-12-01

    Full Text Available The paper deals with the identification of the breakdown of the transformer withdrawn from operation because of repeated reaction of transformer protections. Successively the transformer was put of operation, removed from the distribution and put to diagnostic measurements. The analysis SFRA contributed to the interturn short circuit.

  18. A review of the development of portable laser induced breakdown spectroscopy and its applications

    Czech Academy of Sciences Publication Activity Database

    Rakovský, Jozef; Čermák, P.; Musset, O.; Veis, P.

    2014-01-01

    Roč. 101, NOV 2014 (2014), s. 269-287. ISSN 0584-8547 R&D Projects: GA ČR GA13-11635S Institutional support: RVO:61388955 Keywords : Fiber laser * Fieldable LIBS * Laser-induced breakdown spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.176, year: 2014

  19. Ionization processes in a transient hollow cathode discharge 100 ns before the electrical breakdown

    International Nuclear Information System (INIS)

    A Transient Hollow Cathode Discharge (THCD) is a low-pressure high-voltage electric discharge characterized by the presence of an axial aperture in the cathode [1]. The enhanced ionization processes which take place inside the hollow cathode region (HCR) under strongly modified field conditions (third regimen) are essential events which lead to final electrical breakdown. The main effect of the cathode aperture is to modify the geometry of the externally applied field close of the cathode, to create conditions for local ionization in the HCR well before significant ionization builds up in the anode-cathode gap [2] In previous works [3] it was statistically studied the third and last regime of ionization growth before electrical breakdown, and it was suggested that more than one competing processes take place, both close and inside the HCR, just before breakdown. Statistical analyze of experimental data is presented in order to suggest a temporal sequence of the ionization processes in the third regime of a THCD prior the electrical breakdown. (Author)

  20. Communication Breakdown at Home and at School in Young Children with Cerebral Palsy and Severe Disabilities

    Science.gov (United States)

    Snell, Martha E.; Chen, Lih-Yuan; Allaire, Janet H.; Park, Eunhye

    2008-01-01

    Data about communication breakdown were gathered through interviews of care providers and mailed surveys of special education teachers and speech and language pathologists of 17 children with cerebral palsy and significant language delay. Most care providers indicated that children used personalized communication systems and that these frequently…

  1. Ultra-Low Breakdown Voltage of Field Ionization in Atmospheric Air Based on Silicon Nanowires

    International Nuclear Information System (INIS)

    Classic field ionization requires extremely high positive electric fields, of the order of a few million volts per centimeter. Here we show that field ionization can occur at dramatically lower fields on the electrode of silicon nanowires (SiNWs) with dense surface states and large field enhancement factor. A field ionization structure using SiNWs as the anode has been investigated, in which the SiNWs were fabricated by improved chemical etching process. At room temperature and atmospheric pressure, breakdown of the air is reproducible with a fixed anode-to-cathode distance of 0.5 μm. The breakdown voltage is ∼38 V, low enough to be achieved by a battery-powered unit. Two reasons can be given for the low breakdown voltage. First, the gas discharge departs from the Paschen's law and the breakdown voltage decreases sharply as the gap distance falls in μm range. The other reason is the large electric field enhancement factor (β) and the high density of surface defects, which cause a highly non-uniform electric field for field emission to occur

  2. Lignans from Carthamus tinctorius suppress tryptophan breakdown via indoleamine 2,3-dioxygenase.

    Science.gov (United States)

    Kuehnl, Susanne; Schroecksnadel, Sebastian; Temml, Veronika; Gostner, Johanna M; Schennach, Harald; Schuster, Daniela; Schwaiger, Stefan; Rollinger, Judith M; Fuchs, Dietmar; Stuppner, Hermann

    2013-10-15

    Seed extracts of Carthamus tinctorius L. (Asteraceae), safflower, have been traditionally used to treat coronary disease, thrombotic disorders, and menstrual problems but also against cancer and depression. A possible effect of C. tinctorius compounds on tryptophan-degrading activity of enzyme indoleamine 2,3-dioxygenase (IDO) could explain many of its activities. To test for an effect of C. tinctorius extracts and isolated compounds on cytokine-induced IDO activity in immunocompetent cells in vitro methanol and ethylacetate seed extracts were prepared from cold pressed seed cakes of C. tinctorius and three lignan derivatives, trachelogenin, arctigenin and matairesinol were isolated. The influence on tryptophan breakdown was investigated in peripheral blood mononuclear cells (PBMCs). Effects were compared to neopterin production in the same cellular assay. Both seed extracts suppressed tryptophan breakdown in stimulated PBMC. The three structurally closely related isolates exerted differing suppressive activity on PBMC: arctigenin (IC50 26.5μM) and trachelogenin (IC50 of 57.4μM) showed higher activity than matairesinol (IC50 >200μM) to inhibit tryptophan breakdown. Effects on neopterin production were similar albeit generally less strong. Data show an immunosuppressive property of compounds which slows down IDO activity. The in vitro results support the view that some of the anti-inflammatory, anticancer and antidepressant properties of C. tinctorius lignans might relate to their suppressive influence on tryptophan breakdown. PMID:23867649

  3. Drought, mutualism breakdown, and landscape-scale degradation of seagrass beds

    NARCIS (Netherlands)

    de Fouw, Jimmy; Govers, Laura L; van de Koppel, Johan; van Belzen, Jim; Dorigo, Wouter; Sidi Cheikh, Mohammed A; Christianen, Marjolijn J A; van der Reijden, Karin J; van der Geest, Matthijs; Piersma, Theunis; Smolders, Alfons J P; Olff, Han; Lamers, Leon P M; van Gils, Jan A; van der Heide, Tjisse

    2016-01-01

    In many marine ecosystems, biodiversity critically depends on foundation species such as corals and seagrasses that engage in mutualistic interactions [1-3]. Concerns grow that environmental disruption of marine mutualisms exacerbates ecosystem degradation, with breakdown of the obligate coral mutua

  4. Air breakdown induced by a high-power short-pulse microwave

    International Nuclear Information System (INIS)

    At Himeji Institute of Technology, the high power microwaves with the peak power of 20 MW, frequency of 12 GHz and pulse duration of 14 ns have been produced with a virtual cathode oscillator (vircator). These high power microwaves offer new applications in various fields. One problem in laser-triggered lightning experiment is the strong attenuation of laser energy by rain, cloud and laser-produced plasma. Microwaves propagate in thundercloud with small loss, and also are able to irradiate much extensive region of targets. In this paper, the fundamental experiment on the air breakdown induced by high power, short pulse microwaves is reported. The experimental setup of the vircator diode for microwave generation is shown. The typical evolution of diode voltage, electron beam current and microwave emission from the top in the course of time is shown. The experimental setup for microwave-induced air breakdown and the experimental procedure are explained. The results of negative polarity and positive polarity are reported. In the pressure range lower than 150 Torr, microwave-induced breakdown occurred without corona discharge in both polarities. Microwave-induced breakdown occurred more easily in negative polarity than in positive polarity. (K.I.)

  5. Air breakdown induced by a high-power short-pulse microwave

    Energy Technology Data Exchange (ETDEWEB)

    Wakisaka, T.; Yatsuzuka, M.; Nobuhara, S. [Himeji Inst. of Tech., Hyogo (Japan)

    1996-05-01

    At Himeji Institute of Technology, the high power microwaves with the peak power of 20 MW, frequency of 12 GHz and pulse duration of 14 ns have been produced with a virtual cathode oscillator (vircator). These high power microwaves offer new applications in various fields. One problem in laser-triggered lightning experiment is the strong attenuation of laser energy by rain, cloud and laser-produced plasma. Microwaves propagate in thundercloud with small loss, and also are able to irradiate much extensive region of targets. In this paper, the fundamental experiment on the air breakdown induced by high power, short pulse microwaves is reported. The experimental setup of the vircator diode for microwave generation is shown. The typical evolution of diode voltage, electron beam current and microwave emission from the top in the course of time is shown. The experimental setup for microwave-induced air breakdown and the experimental procedure are explained. The results of negative polarity and positive polarity are reported. In the pressure range lower than 150 Torr, microwave-induced breakdown occurred without corona discharge in both polarities. Microwave-induced breakdown occurred more easily in negative polarity than in positive polarity. (K.I.)

  6. Effect of surface-breakdown plasma on metal drilling by pulsed CO2-laser radiation

    Science.gov (United States)

    Arutiunian, P. V.; Baranov, V. Iu.; Bobkov, I. V.; Bol'Shakov, L. A.; Dolgov, V. A.

    1988-03-01

    The effect of low-threshold surface breakdown produced by short (5-microsec) CO2-laser pulses on the metal drilling process is investigated. Data on the interaction of metals with laser pulses having the same duration but different shape are shown to be different. The effect of the ambient atmospheric pressure on the laser drilling process is investigated.

  7. Three-dimensional vortex analysis and aeroacoustic source characterization of jet core breakdown

    NARCIS (Netherlands)

    Violato, D.; Scarano, F.

    2013-01-01

    The three-dimensional behavior of jet core breakdown is investigated with experiments conducted on a free water jet at Re = 5000 by time-resolved tomographic particle image velocimetry (TR-TOMO PIV). The investigated domain encompasses the range between 0 and 10 jet diameters. The characteristic pul

  8. Tensile stress generation by optical breakdown in tissue: Experimental investigations and numerical simulations

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, A. [Medizinisches Laserzentrum Luebeck (Germany); Scammon, R.J.; Godwin, R.P. [Los Alamos National Lab., NM (United States)

    1999-03-01

    Biological tissue is more susceptible to damage from tensile stress than to compressive stress. Tensile stress may arise through the thermoelastic response of laser-irradiated media. Optical breakdown, however, has to date been exclusively associated with compressive stress. The authors show that this is appropriate for water, but not for tissues for which the elastic-plastic material response needs to be considered. The acoustic transients following optical breakdown in water and cornea were measured with a fast hydrophone and the cavitation bubble dynamics, which is closely linked to the stress wave generation, was documented by flash photography. Breakdown in water produced a monopolar acoustic signal and a bubble oscillation in which the expansion and collapse phases were symmetric. Breakdown in cornea produced a bipolar acoustic signal coupled with a pronounced shortening of the bubble expansion phase and a considerable prolongation of its collapse phase. The tensile stress wave is related to the abrupt end of the bubble expansion. Numerical simulations using the MESA-2D code were performed assuming elastic-plastic material behavior in a wide range of values for the shear modulus and yield strength. The calculations revealed that consideration of the elastic-plastic material response is essential to reproduce the experimentally observed bipolar stress waves. The tensile stress evolves during the outward propagation of the acoustic transient and reaches an amplitude of 30--40% of the compressive pulse.

  9. The influence of titanium dioxide additive on the short-term DC breakdown strength of polyethylene

    DEFF Research Database (Denmark)

    Khalil, M. S; Henk, Peter O; Henriksen, Mogens

    1990-01-01

    The effect of the addition of 1% by weight of titanium dioxide fine particles to low-density polyethylene (LDPE) on the short-term DC breakdown strength of the LDPE was investigated using direct and reverse polarity voltages. The samples used were cylinders of both plain and doped materials, with...

  10. Control of vortex breakdown in a closed cylinder with a small rotating rod

    DEFF Research Database (Denmark)

    Lo Jacono, D.; Sørensen, Jens Nørkær; Thompson, M.C.; Hourigan, K.

    2008-01-01

    Effective control of vortex breakdown in a cylinder with a rotating lid was achieved with small rotating rods positioned on the stationary lid. After validation with accurate measurements using a novel stereoscopic particle image velocimetry (SPIV) technique, analysis of numerical simulations using...

  11. Maitotoxin: Effects on calcium channels, phosphoinositide breakdown, and arachidonate release in pheochromocytoma PC12 cells

    International Nuclear Information System (INIS)

    Maitotoxin (MTX) increases formation of [3H]inositol phosphates from phosphoinositides and release of [3H]arachidonic acid from phospholipids in pheochromocytoma PC12 cells. Formation of [3H]inositol phosphates is detected within 1 min of incubation even with concentrations as low as 0.3 ng/ml (90 pm) MTX, whereas release of [3H]arachidonic acid is not detected until 20 min even with concentrations as high as 1 ng/ml (300 pm) MTX. Stimulation of arachidonic acid release can be detected at 0.03 ng/ml (9 pm) MTX, whereas 0.1 ng/ml (30 pm) MTX is the threshold for detection of phosphoinositide breakdown. Organic and inorganic calcium channel blockers, except Cd2+ and a high concentration of Mn2+, have no effect on MTX-elicited phosphoinositide breakdown, whereas inorganic blockers (e.g., Co2+, Mn2+, Cd2+), but not organic blockers (nifedipine, verapamil, diltiazem), inhibit MTX-stimulated arachidonic acid release. All calcium channel blockers, however, inhibited MTX-elicited influx of 45Ca2+ and the MTX-elicited increase in internal Ca2+ measured with fura-2 was markedly reduced by nifedipine. MTX-elicited phosphoinositide breakdown and arachidonic acid release are abolished or reduced, respectively, in the absence of extracellular calcium plus chelating agent. The calcium ionophore A23187 has little or no effect alone but, in combination with MTX, A23187 inhibits MTX-elicited phosphoinositide breakdown and enhances arachidonic acid release, the latter even in the absence of extracellular calcium. The results suggest that different sites and/or mechanisms are involved in stimulation of calcium influx, breakdown of phosphoinositides, and release of arachidonic acid by MTX

  12. Drought, Mutualism Breakdown, and Landscape-Scale Degradation of Seagrass Beds.

    Science.gov (United States)

    de Fouw, Jimmy; Govers, Laura L; van de Koppel, Johan; van Belzen, Jim; Dorigo, Wouter; Sidi Cheikh, Mohammed A; Christianen, Marjolijn J A; van der Reijden, Karin J; van der Geest, Matthijs; Piersma, Theunis; Smolders, Alfons J P; Olff, Han; Lamers, Leon P M; van Gils, Jan A; van der Heide, Tjisse

    2016-04-25

    In many marine ecosystems, biodiversity critically depends on foundation species such as corals and seagrasses that engage in mutualistic interactions [1-3]. Concerns grow that environmental disruption of marine mutualisms exacerbates ecosystem degradation, with breakdown of the obligate coral mutualism ("coral bleaching") being an iconic example [2, 4, 5]. However, as these mutualisms are mostly facultative rather than obligate, it remains unclear whether mutualism breakdown is a common risk in marine ecosystems, and thus a potential accelerator of ecosystem degradation. Here, we provide evidence that drought triggered landscape-scale seagrass degradation and show the consequent failure of a facultative mutualistic feedback between seagrass and sulfide-consuming lucinid bivalves that in turn appeared to exacerbate the observed collapse. Local climate and remote sensing analyses revealed seagrass collapse after a summer with intense low-tide drought stress. Potential analysis-a novel approach to detect feedback-mediated state shifts-revealed two attractors (healthy and degraded states) during the collapse, suggesting that the drought disrupted internal feedbacks to cause abrupt, patch-wise degradation. Field measurements comparing degraded patches that were healthy before the collapse with patches that remained healthy demonstrated that bivalves declined dramatically in degrading patches with associated high sediment sulfide concentrations, confirming the breakdown of the mutualistic seagrass-lucinid feedback. Our findings indicate that drought triggered mutualism breakdown, resulting in toxic sulfide concentrations that aggravated seagrass degradation. We conclude that external disturbances can cause sudden breakdown of facultative marine mutualistic feedbacks. As this may amplify ecosystem degradation, we suggest including mutualisms in marine conservation and restoration approaches. PMID:26972316

  13. Influence of VUV illumination on breakdown mechanics: pre-ionization, direct photoionization, and discharge initiation

    International Nuclear Information System (INIS)

    A microdischarge (MD) vacuum ultraviolet (VUV) light source is fired onto a N2–NO (99.92 : 0.08%) target gas. The minor gas constituent, NO, was chosen for its ionization potential (9.23 eV) and photoionization cross-section (1.4 × 10−18 cm2) at the wavelength of interest (121.6 nm, 10.2 eV). The result is a plasma generated entirely by volume photoionization in a N2–NO background. Using a very low electric field amplitude, charge carriers are drifted though the photoplasma at picoampere levels, serving as a non-invasive diagnostic. Using a simple one-dimensional fluid approximation for the low electric field condition, theoretical predictions of photoplasma current were found to be in meaningful agreement with experimental data. The impact of direct photoionization and pre-ionization on nanosecond timescale high voltage breakdown yielded two primary observations: (1) a significant reduction in the formative delay time necessary for spark formation, and (2) almost complete elimination of the statistical delay time. Again utilizing one-dimensional fluid approximations, reasonable agreement between experimental and simulated breakdown voltage was observed. Utilizing the same VUV source to illuminate a HV spark gap biased to about 95% self-breakdown voltage revealed that direct volume photoionization alone was insufficient to trigger breakdown of the high voltage gap. However, permitting electrode illumination, the same source was found to be capable of triggering breakdown in the undervoltaged gap, albeit with a large temporal jitter. (paper)

  14. Influence of magnetic field on the electric breakdown in penning ion source

    Science.gov (United States)

    Mahjour-Shafiei, M.; Noori, H.; Ranjbar, A. H.

    2011-11-01

    A cold-cathode penning-type ion source has been developed in our laboratory to study the electric breakdown in this type of sources. The breakdown voltage was measured as a function of axial magnetic field, in the range of 440-600 G, and anode length, in steps of 14, 20, and 24 mm. The measurement was performed with stainless steel cathodes in argon gas at pressure of 4 × 10-2 mbar. Furthermore, a model was developed to explain the breakdown voltage data. In the construction of the model, the first Townsend coefficient was not directly used to avoid difficulties originating from the non-uniformity of the electric field. The empirical parameters of the model were obtained using the experimental data. The equation γ = c × (Ez/N)n, expressing the effective secondary emission coefficient in terms of reduced electric field, which was needed in the modeling process, was inspired from previous works. The parameters c and n were then calculated from the empirical parameters of the model. The n parameter turned out to be 0.59, which differs from the value reported by other authors merely by 1.6%. Three values, 0.010, 0.013, and 0.017 corresponding to the three anodes were obtained for the c parameter. These numbers are in good agreement with 0.01, which has been reported in the previous works. It was also found that the value of n has a decisive impact on the breakdown voltage curve in the high breakdown voltage region.

  15. Influence of magnetic field on the electric breakdown in penning ion source.

    Science.gov (United States)

    Mahjour-Shafiei, M; Noori, H; Ranjbar, A H

    2011-11-01

    A cold-cathode penning-type ion source has been developed in our laboratory to study the electric breakdown in this type of sources. The breakdown voltage was measured as a function of axial magnetic field, in the range of 440-600 G, and anode length, in steps of 14, 20, and 24 mm. The measurement was performed with stainless steel cathodes in argon gas at pressure of 4 × 10(-2) mbar. Furthermore, a model was developed to explain the breakdown voltage data. In the construction of the model, the first Townsend coefficient was not directly used to avoid difficulties originating from the non-uniformity of the electric field. The empirical parameters of the model were obtained using the experimental data. The equation γ = c × (E(z)/N)(n), expressing the effective secondary emission coefficient in terms of reduced electric field, which was needed in the modeling process, was inspired from previous works. The parameters c and n were then calculated from the empirical parameters of the model. The n parameter turned out to be 0.59, which differs from the value reported by other authors merely by 1.6%. Three values, 0.010, 0.013, and 0.017 corresponding to the three anodes were obtained for the c parameter. These numbers are in good agreement with 0.01, which has been reported in the previous works. It was also found that the value of n has a decisive impact on the breakdown voltage curve in the high breakdown voltage region. PMID:22128971

  16. Stress wave emission and cavitation bubble dynamics by nanosecond optical breakdown in a tissue phantom

    Science.gov (United States)

    Brujan, Emil-Alexandru; Vogel, Alfred

    2006-07-01

    Stress wave emission and cavitation bubble dynamics after optical breakdown in water and a tissue phantom with Nd: YAG laser pulses of 6 ns duration were investigated both experimentally and numerically to obtain a better understanding of the physical mechanisms involved in plasma-mediated laser surgery. Experimental tools were high-speed photography with 50000 frames s(-1) , and acoustic measurements. The tissue phantom consisted of a transparent polyacrylamide (PAA) gel, the elastic properties of which can be controlled by modifying the water content. Breakdown in water produced a purely compressive stress wave. By contrast, in stiff PAA samples and for sufficiently large pulse energies, the compression wave was followed by an intense tensile wave, similar to the behaviour previously observed in cornea. The elastic/plastic response of the medium led to a significant decrease of the maximum size of the cavitation bubble and to a shortening of its oscillation period which was found to be related to the generation of the tensile stress wave upon breakdown. For increasing elastic modulus of the PAA, both the amplitudes of the bubble oscillation and of the stress wave emitted during bubble collapse decreased until the bubble oscillation was so strongly damped that no collapse stress wave was emitted. Numerical simulations were performed using a spherical model of bubble dynamics which includes the compressibility and elastic/plastic behaviour of the medium, viscosity, density and surface tension. The calculations revealed that consideration of the elastic/plastic behaviour of the medium surrounding the bubble is essential to describe the experimentally observed bipolar shape of the stress wave emitted upon optical breakdown. Water is a poor tissue model because the shape of the emitted stress waves and the bubble dynamics differ strongly for both materials. The mechanical properties of PAA were also found to be quite different from those of tissues. Experimental and

  17. Use of a liquid-phase ion gun for local breakdown of the passive film on iron

    Energy Technology Data Exchange (ETDEWEB)

    Fushimi, Koji; Azumi, Kazuhisa; Seo, Masahiro

    2000-02-01

    A silver/silver chloride microelectrode was developed as a liquid-phase ion gun for investigation of precursor processes of pitting corrosion. This electrode was set as a probe electrode of a scanning electrochemical microscope and used to induce a local breakdown of passive film on iron. A small amount of chloride ions generated by cathodic polarization of the silver/silver chloride microelectrode has succeeded in inducing the local breakdown of the passive film formed on iron in deaerated pH 6.5 borate solution. Moreover, the microelectrode could detect ferric ions dissolved from the film at the initial stage of the film breakdown.

  18. Schottky barrier breakdown in Si stimulation by exciton drift in inhomogeneous electric field at 4.2 K

    International Nuclear Information System (INIS)

    Experimental study of the mechanism of the Schottky barrier breakdown stimulation in photoexcited silicon in the strong electric field at 4.2 K is presented. The effect of photoexcitation intensity and the intensity of the electric field applied, as well as the influence of their time on breakdown mechanism were studied. It is shown that Schottky barrier breakdown occurs due to the narrowing of the spatial charged region caused by the exciton drift under the inhomogeneous electric field and electron recombination at the barrier ionized impurity levels

  19. Breakdown of C3 after complement activation. Identification of a new fragment C3g, using monoclonal antibodies

    OpenAIRE

    1982-01-01

    The physiological breakdown of C3 has been studied using monoclonal anti-C3 antibodies, and it has been found that the later stages of this process--the breakdown of C3bi--is more complex than had previously been recognized. C3bi is the reaction product produced from C3b by the action of factor I which, in the presence of factor H, produces a double cleavage in the alpha chain of C3b. It is here reported that, both on cells and in the fluid phase, the breakdown of C3bi in serum gives rise to ...

  20. Meiosis, egg activation, and nuclear envelope breakdown are differentially reliant on Ca2+, whereas germinal vesicle breakdown is Ca2+ independent in the mouse oocyte

    Science.gov (United States)

    Tombes, R. M.; Simerly, C.; Borisy, G. G.; Schatten, G.

    1992-01-01

    During early development, intracellular Ca2+ mobilization is not only essential for fertilization, but has also been implicated during other meiotic and mitotic events, such as germinal vesicle breakdown (GVBD) and nuclear envelope breakdown (NEBD). In this study, the roles of intracellular and extracellular Ca2+ were examined during meiotic maturation and reinitiation at parthenogenetic activation and during first mitosis in a single species using the same methodologies. Cumulus-free metaphase II mouse oocytes immediately resumed anaphase upon the induction of a large, transient Ca2+ elevation. This resumption of meiosis and associated events, such as cortical granule discharge, were not sensitive to extracellular Ca2+ removal, but were blocked by intracellular Ca2+ chelators. In contrast, meiosis I was dependent on external Ca2+; in its absence, the formation and function of the first meiotic spindle was delayed, the first polar body did not form and an interphase-like state was induced. GVBD was not dependent on external Ca2+ and showed no associated Ca2+ changes. NEBD at first mitosis in fertilized eggs, on the other hand, was frequently, but not always associated with a brief Ca2+ transient and was dependent on Ca2+ mobilization. We conclude that GVBD is Ca2+ independent, but that the dependence of NEBD on Ca2+ suggests regulation by more than one pathway. As cells develop from Ca(2+)-independent germinal vesicle oocytes to internal Ca(2+)-dependent pronuclear eggs, internal Ca2+ pools increase by approximately fourfold.

  1. Comparison of the Detection Characteristics of Trace Species Using Laser-Induced Breakdown Spectroscopy and Laser Breakdown Time-of-Flight Mass Spectrometry

    Directory of Open Access Journals (Sweden)

    Zhenzhen Wang

    2015-03-01

    Full Text Available The rapid and precise element measurement of trace species, such as mercury, iodine, strontium, cesium, etc. is imperative for various applications, especially for industrial needs. The elements mercury and iodine were measured by two detection methods for comparison of the corresponding detection features. A laser beam was focused to induce plasma. Emission and ion signals were detected using laser-induced breakdown spectroscopy (LIBS and laser breakdown time-of-flight mass spectrometry (LB-TOFMS. Multi-photon ionization and electron impact ionization in the plasma generation process can be controlled by the pressure and pulse width. The effect of electron impact ionization on continuum emission, coexisting molecular and atomic emissions became weakened in low pressure condition. When the pressure was less than 1 Pa, the plasma was induced by laser dissociation and multi-photon ionization in LB-TOFMS. According to the experimental results, the detection limits of mercury and iodine in N2 were 3.5 ppb and 60 ppb using low pressure LIBS. The mercury and iodine detection limits using LB-TOFMS were 1.2 ppb and 9.0 ppb, which were enhanced due to different detection features. The detection systems of LIBS and LB-TOFMS can be selected depending on the condition of each application.

  2. Gas-dynamic phenomena during self-healing electrical breakdowns in an organic dielectric

    Energy Technology Data Exchange (ETDEWEB)

    Kammermaier, J.

    1983-01-01

    Breakdown sparks cause a dielectric to decompose close to the edges of the vapor-deposited metal electrodes due to the bremsstrahlung of the plasma electrons in atoms. The resulting gaseous phase is distributed according to gas-dynamic laws and remains separated from the spark plasma by a tangential contact discontinuity. At zero flow the pressure and density are identical in both gaseous phases. Equilibrium reactions convert the atoms of the decomposed dielectric into CO and numerous Csub(m)Hsub(n) compounds, some of which are subject to further reactions as they cool down. The developed model is used for calculating the gasification relevant to self-healing during electrical breakdowns in polypropylene.

  3. High glycogen levels enhance glycogen breakdown in isolated contracting skeletal muscle

    DEFF Research Database (Denmark)

    Richter, Erik; Galbo, H

    1986-01-01

    after 15 min of intermittent electrical muscle stimulation. Before stimulation, glycogen was higher in rats that swam on the preceding day (supercompensated rats) compared with controls. During muscle contractions, glycogen breakdown in fast-twitch red and white fibers was larger in supercompensated......The influence of supranormal muscle glycogen levels on glycogen breakdown in contracting muscle was investigated. Rats either rested or swam for 3 h and subsequently had their isolated hindquarters perfused after 21 h with access to food. Muscle glycogen concentrations were measured before and...... hindquarters than in controls, and glycogenolysis correlated significantly with precontraction glycogen concentrations. In slow-twitch fibers, electrical stimulation did not elicit glycogenolysis in either group. Glucose uptake and lactate release were decreased and increased, respectively, in supercompensated...

  4. Temporal And Spatial Characterization Of Optical Breakdown In A Suspension Of Small Absorbing Particles

    Science.gov (United States)

    Nashold, Karen M.; Brown, Robert A.; Walter, Diane P.; Honey, Richard C.

    1989-08-01

    It has been shown that a suspension of small, absorbing particles in a liquid demonstrates nonlinear transmission when exposed to high-energy laser pulses. Two experiments were performed to characterize the nonlinear phenomena that occur. First, an HeNe probe beam and fast photodetector were used to monitor the transmission of the suspension as high-intensity Nd:YAG pulses passed through. The sequence of events in the breakdown process was thus determined. Second, the spatial distribution of the transmitted Nd:YAG pulses was monitored with a CCD camera and Quantex QX-7 digital image processor. The distribution of the light scattered by the suspension was viewed for input pulses less than, near to, and greater than the threshold required to produce breakdown. The combined results of these two experiments gives a clearer understanding of the limiting process that occurs.

  5. Loss of Myelin Basic Protein Function Triggers Myelin Breakdown in Models of Demyelinating Diseases.

    Science.gov (United States)

    Weil, Marie-Theres; Möbius, Wiebke; Winkler, Anne; Ruhwedel, Torben; Wrzos, Claudia; Romanelli, Elisa; Bennett, Jeffrey L; Enz, Lukas; Goebels, Norbert; Nave, Klaus-Armin; Kerschensteiner, Martin; Schaeren-Wiemers, Nicole; Stadelmann, Christine; Simons, Mikael

    2016-07-12

    Breakdown of myelin sheaths is a pathological hallmark of several autoimmune diseases of the nervous system. We employed autoantibody-mediated animal models of demyelinating diseases, including a rat model of neuromyelitis optica (NMO), to target myelin and found that myelin lamellae are broken down into vesicular structures at the innermost region of the myelin sheath. We demonstrated that myelin basic proteins (MBP), which form a polymer in between the myelin membrane layers, are targeted in these models. Elevation of intracellular Ca(2+) levels resulted in MBP network disassembly and myelin vesiculation. We propose that the aberrant phase transition of MBP molecules from their cohesive to soluble and non-adhesive state is a mechanism triggering myelin breakdown in NMO and possibly in other demyelinating diseases. PMID:27346352

  6. Magnetic field analysis during breakdown phase in the low loop resistance tokamak HT-2

    Energy Technology Data Exchange (ETDEWEB)

    Abe, Mitsushi; Doi, Akira; Takeuchi, Kazuhiro; Otsuka, Michio (Hitachi Ltd., Ibaraki (Japan). Energy Research Lab.); Nishio, Satoshi; Sugihara, Masayoshi; Yoshino, Ryuji; Okazaki, Takashi

    1994-06-01

    The magnetic analysis code SHP was improved in order to understand the poloidal magnetic field during the breakdown phase of the Hitachi tokamak HT-2, which had its loop resistance modified to a very low value. The SHP code uses a model with filamental loop currents in the plasma area. Its improvements are the following. (1) The eddy currents on the vacuum vessel, which are assumed to be uniform in the toroidal direction, are expanded by distribution functions obtained by a singular value decomposition of a projection matrix from the eddy currents to the flux distribution on the plasma surface area. (2) The magnetic field due to the iron core biasing current and the stray horizontal field of the toroidal field coils are compensated. After improvements, it was confirmed that the poloidal field null point was generated before breakdown and the SHP results were consistent with discharge photographs taken by a high speed camera. (author).

  7. Experimental study of time-dependent dielectric breakdown in tri-gate nanowire transistor

    Science.gov (United States)

    Ota, Kensuke; Tanaka, Chika; Numata, Toshinori; Matsushita, Daisuke; Saitoh, Masumi

    2016-08-01

    We systematically investigate the size dependence of the time-dependent dielectric breakdown (TDDB) in a tri-gate nanowire transistor (NW Tr.). It is newly found that TDDB reliability is degraded in NW Tr. as compared with that in a planar transistor owing to the locally enhanced electric field at the NW corner. Moreover, in the region with a width (W) less than 40 nm, nanowire width reduction leads to a shorter time to gate dielectric breakdown indicating additional degradation of TDDB reliability in NW Tr. with smaller W. Although TDDB in three-dimensional (3D) MOS structures such as a trench MOS capacitor has already been reported, the size dependence of TDDB in scaled NW Tr. is firstly discussed in this paper since a trench capacitor is different from recent NW Tr. in structure, device size, gate dielectric thickness, and scaling effect on TDDB.

  8. RF-Breakdown kicks at the CTF3 two-beam test stand

    CERN Document Server

    Palaia, Andrea; Muranaka, Tomoko; Ruber, Roger; Ziemann, V; Farabolini, W

    2012-01-01

    The measurement of the effects of RF-breakdown on the beam in CLIC prototype accelerator structures is one of the key aspects of the CLIC two-beam acceleration scheme being addressed at the Two-beam Test Stand (TBTS) at CTF3. RF-breakdown can randomly cause energy loss and transverse kicks to the beam. Transverse kicks have been measured by means of a screen intercepting the beam after the accelerator structure. In correspondence of a RFbreakdown we detect a double beam spot which we interpret as a sudden change of the beam trajectory within a single beam pulse. To time-resolve such effect, the TBTS has been equipped with five inductive Beam Position Monitors (BPMs) and a spectrometer line to measure both relative changes of the beam trajectory and energy losses. Here we discuss the methodology used and we present the latest results of such measurements

  9. Manipulating Tabu List to Handle Machine Breakdowns in Job Shop Scheduling Problems

    Science.gov (United States)

    Nababan, Erna Budhiarti; SalimSitompul, Opim

    2011-06-01

    Machine breakdowns in a production schedule may occur on a random basis that make the well-known hard combinatorial problem of Job Shop Scheduling Problems (JSSP) becomes more complex. One of popular techniques used to solve the combinatorial problems is Tabu Search. In this technique, moves that will be not allowed to be revisited are retained in a tabu list in order to avoid in gaining solutions that have been obtained previously. In this paper, we propose an algorithm to employ a second tabu list to keep broken machines, in addition to the tabu list that keeps the moves. The period of how long the broken machines will be kept on the list is categorized using fuzzy membership function. Our technique are tested to the benchmark data of JSSP available on the OR library. From the experiment, we found that our algorithm is promising to help a decision maker to face the event of machine breakdowns.

  10. Experimental study of electric breakdowns in liquid argon at centimeter scale

    CERN Document Server

    Blatter, A; Hsu, C -C; Janos, S; Kreslo, I; Luethi, M; von Rohr, C Rudolf; Schenk, M; Strauss, T; Weber, M S; Zeller, M

    2014-01-01

    In this paper we present results on measurements of the dielectric strength of liquid argon near its boiling point and cathode-anode distances in the range of 0.1 mm to 40 mm with spherical cathode and plane anode. We show that at such distances the applied electric field at which breakdowns occur is as low as 40 kV/cm. Flash-overs across the ribbed dielectric of the high voltage feed-through are observed for a length of 300 mm starting from a voltage of 55 kV. These results contribute to set reference for the breakdown-free design of ionization detectors, such as Liquid Argon Time Projection Chambers (LAr TPC).

  11. Investigation Of Breakdown Induced Surface Damage On 805 Mhz Pillbox Cavity Interior Surfaces

    CERN Document Server

    Jana, M R; Leonova, M; Moretti, A; Tollestrup, A; Yonehara, K; Freemire, B; Torun, Y; Bowring, D; Flanagan, G

    2014-01-01

    The MuCool Test Area (MTA) at Fermilab is a facility to develop the technology required for ionization cooling for a future Muon Collider and/or Neutrino Factory. As part of this research program, we have tested two 805 MHz vacuum RF cavities in a multi-Tesla magnetic field to study the effects of the static magnetic field on the cavity operation. This study gives useful information on field emitters in the cavity, dark current, surface conditioning, breakdown mechanisms and material properties of the cavity. All these factors determine the maximum accelerating gradient in the cavity. This paper discusses the image processing technique for quantitative estimation of spark damage spot distribution on cavity interior surfaces. The distribution is compared with the electric field distribution predicted by a computer code calculation. The local spark density is proportional to probability of surface breakdown and shows a power law dependence on the maximum electric field (E). This E dependence is consistent with ...

  12. Why isolated streamer discharges hardly exist above the breakdown field in atmospheric air

    CERN Document Server

    Sun, A B; Ebert, U

    2013-01-01

    We investigate streamer formation in the troposphere, in electric fields above the breakdown threshold. With fully three-dimensional particle simulations, we study the combined effect of natural background ionization and of photoionization on the discharge morphology. In previous investigations based on deterministic fluid models without background ionization, so-called double-headed streamers emerged. But in our improved model, many electron avalanches start to grow at different locations. Eventually the avalanches collectively screen the electric field in the interior of the discharge. This happens after what we call the `ionization screening time', for which we give an analytical estimate. As this time is comparable to the streamer formation time, we conclude that isolated streamers are unlikely to exist in fields well above breakdown in atmospheric air.

  13. Performance evaluation of self-breakdown-based single-gap plasma cathode electron gun

    Indian Academy of Sciences (India)

    Niraj Kumar; Nalini Pareek; Udit Narayan Pal; Deepak Kumar Verma; Jitendra Prajapati; Mahesh Kumar; Bharat Lal Meena; Ram Prakash

    2014-06-01

    This paper presents the experimental studies on self-breakdown-based single-gap plasma cathode electron (PCE) gun (5–20 kV/50–160 A) in argon, gas atmosphere and its performance evaluation based on particle-in-cell (PIC) simulation code `OOPIC-Pro’.The PCE-Gun works in conducting phase (low energy, high current) of pseudospark discharge. It produces an intense electron beam, which can propagate more than 200 mm in the drift space region without external magnetic field. The profile of this beam in the drift space region at different breakdown conditions (i.e., gas pressures and applied voltages) has been studied and the experimental results are compared with simulated values. It is demonstrated that ∼30% beam current is lost during the propagation possibly due to space charge neutralization and collisions with neutral particles and walls.

  14. Preparation and Arc Breakdown Behavior of Nanocrystalline W-Cu Electrical Contact Materials

    Institute of Scientific and Technical Information of China (English)

    Wenge CHEN; Zhanying KANG; Bingjun DING

    2005-01-01

    Nanostructured (NS) W-Cu composite powder was prepared by mechanical alloying (MA), and nanostructured bulk of W-Cu contact material was fabricated by hot pressed sintering in an electrical vacuum furnace. The microstructure,electric conductivity, hardness, breakdown voltage and arcing time of NS W-Cu alloys were measured and compared to conventional W-Cu alloys prepared by powder metallurgy. The results show that microstructural refinement and uniformity can improve the breakdown behavior, the electric arc stability and the arc extinction ability of nanostructured W-Cu contacts materials. Also, the nanostructured W-Cu contact material shows the characteristic of spreading electric arcs, which is of benefit to electric arc erosion.

  15. Controllable electrical and physical breakdown of poly-crystalline silicon nanowires by thermally assisted electromigration

    Science.gov (United States)

    Park, Jun-Young; Moon, Dong-Il; Seol, Myeong-Lok; Jeon, Chang-Hoon; Jeon, Gwang-Jae; Han, Jin-Woo; Kim, Choong-Ki; Park, Sang-Jae; Lee, Hee Chul; Choi, Yang-Kyu

    2016-01-01

    The importance of poly-crystalline silicon (poly-Si) in semiconductor manufacturing is rapidly increasing due to its highly controllable conductivity and excellent, uniform deposition quality. With the continuing miniaturization of electronic components, low dimensional structures such as 1-dimensional nanowires (NWs) have attracted a great deal of attention. But such components have a much higher current density than 2- or 3- dimensional films, and high current can degrade device lifetime and lead to breakdown problems. Here, we report on the electrical and thermal characteristics of poly-Si NWs, which can also be used to control electrical and physical breakdown under high current density. This work reports a controllable catastrophic change of poly-Si NWs by thermally-assisted electromigration and underlying mechanisms. It also reports the direct and real time observation of these catastrophic changes of poly-Si nanowires for the first time, using scanning electron microscopy.

  16. A numerically accessible criterion for the breakdown of quasi-periodic solutions and its rigorous justification

    International Nuclear Information System (INIS)

    We formulate and justify rigorously a numerically efficient criterion for the computation of the analyticity breakdown of quasi-periodic solutions in symplectic maps (any dimension) and 1D statistical mechanics models. Depending on the physical interpretation of the model, the analyticity breakdown may correspond to the onset of mobility of dislocations, or of spin waves (in the 1D models) and to the onset of global transport in symplectic twist maps in 2D. The criterion proposed here is based on the blow-up of Sobolev norms of the hull functions. We prove theorems that justify the criterion. These theorems are based on an abstract implicit function theorem, which unifies several results in the literature. The proofs also lead to fast algorithms, which have been implemented and used elsewhere. The method can be adapted to other contexts

  17. High breakdown single-crystal GaN p-n diodes by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Molecular beam epitaxy grown GaN p-n vertical diodes are demonstrated on single-crystal GaN substrates. A low leakage current <3 nA/cm2 is obtained with reverse bias voltage up to −20 V. With a 400 nm thick n-drift region, an on-resistance of 0.23 mΩ cm2 is achieved, with a breakdown voltage corresponding to a peak electric field of ∼3.1 MV/cm in GaN. Single-crystal GaN substrates with very low dislocation densities enable the low leakage current and the high breakdown field in the diodes, showing significant potential for MBE growth to attain near-intrinsic performance when the density of dislocations is low

  18. Identification of inks and structural characterization of contemporary artistic prints by laser-induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    Identification of the inks used in artistic prints and the order in which different ink layers have been applied on a paper substrate are important factors to complement the classical stylistic aspects for the authentication of this type of objects. Laser-induced breakdown spectroscopy (LIBS) is investigated to determine the chemical composition and structural distribution of the constituent materials of model prints made by applying one or two layers of several blue and black inks on an Arches paper substrate. By using suitable laser excitation conditions, identification of the inks was possible by virtue of emissions from key elements present in their composition. Analysis of successive spectra on the same spot allowed the identification of the order in which the inks were applied on the paper. The results show the potential of laser-induced breakdown spectroscopy for the chemical and structural characterization of artistic prints

  19. Children Increase Their Sensitivity to a Speaker's Nonlinguistic Cues Following a Communicative Breakdown.

    Science.gov (United States)

    Yow, W Quin; Markman, Ellen M

    2016-03-01

    Bilingual children regularly face communicative challenges when speakers switch languages. To cope with such challenges, children may attempt to discern a speaker's communicative intent, thereby heightening their sensitivity to nonverbal communicative cues. Two studies examined whether such communication breakdowns increase sensitivity to nonverbal cues. English-speaking monolingual (n = 64) and bilingual (n = 54) 3- to 4-year-olds heard instructions in either English only or English mixed with a foreign language. Later, children played a hiding game that relied on nonverbal cues. Hearing a foreign language switch improved both monolingual and bilingual children's use of these cues. Moreover, bilinguals with more prior code-switching exposure outperformed those with less prior code-switching exposure. Children's short-term strategies to repair communication breakdowns may evolve into a more generalizable set of skills. PMID:26841131

  20. Universally Spatial-Temporal Dynamics of Spontaneous Superfluidity Breakdown within Synthetic Gauge Fields

    CERN Document Server

    Wu, Shuyuan; Xu, Jun; Lee, Chaohong

    2016-01-01

    According to the famous Kibble-Zurek mechanism (KZM), the universality of spontaneous defect generation in continuous phase transitions (CPTs) can be understood by the critical slowing down. In most CPTs of atomic Bose-Einstein condensates (BECs), the universality of spontaneous defect generations has been explained by the divergent relaxation time associated with the nontrivial gapless Bogoliubov excitations. However, for atomic BECs in synthetic gauge fields, their spontaneous superfluidity breakdown is resulted from the divergent correlation length associated with the zero Landau critical velocity. Here, by considering an atomic BEC ladder subjected to a synthetic magnetic field, we reveal that the spontaneous superfluidity breakdown obeys the KZM. The Kibble-Zurek scalings are derived from the Landau critical velocity which determines the correlation length. In further, the critical exponents are numerically extracted from the critical spatial-temporal dynamics of the bifurcation delay and the spontaneous...