Production of hydrogen and deuterium negative ions in an electron cyclotron resonance driven plasma

Energy Technology Data Exchange (ETDEWEB)

Dougar-Jabon, V.D. [Industrial Univ. of Santander, Bucaramanga (Colombia)

2001-04-01

An electron cyclotron resonance source with driven plasma rings for hydrogen isotope ion production is studied. Extracted currents of positive and negative ions depending on gas pressure, microwave power value and extraction voltage are obtained. The study shows that the negative ion yield is an order of magnitude higher than the yield of positive particles when a driven ring is in contact with the surface of the plasma electrode. The production of negative ions of deuterium, D{sup -}, is close to the production of negative ions of light hydrogen isotope, H{sup -}. The comparison of the experimental data with the calculated ones shows that the most probable process of the H{sup -} and D{sup -} ion formation in the electron cyclotron driven plasma is dissociative attachment of electrons to molecules in high Rydberg states. For hydrogen ions and ions of deuterium, the negative current at a microwave power of 200 W through a 3-mm aperture and 8 kV extraction voltage are 4.7 mA and 3.1 mA respectively. (orig.)

Production of hydrogen and deuterium negative ions in an electron cyclotron resonance driven plasma

International Nuclear Information System (INIS)

Dougar-Jabon, V.D.

2001-01-01

An electron cyclotron resonance source with driven plasma rings for hydrogen isotope ion production is studied. Extracted currents of positive and negative ions depending on gas pressure, microwave power value and extraction voltage are obtained. The study shows that the negative ion yield is an order of magnitude higher than the yield of positive particles when a driven ring is in contact with the surface of the plasma electrode. The production of negative ions of deuterium, D - , is close to the production of negative ions of light hydrogen isotope, H - . The comparison of the experimental data with the calculated ones shows that the most probable process of the H - and D - ion formation in the electron cyclotron driven plasma is dissociative attachment of electrons to molecules in high Rydberg states. For hydrogen ions and ions of deuterium, the negative current at a microwave power of 200 W through a 3-mm aperture and 8 kV extraction voltage are 4.7 mA and 3.1 mA respectively. (orig.)

Verification of the effects of Schumann frequency range electromagnetic fields on the human cardiovascular system

Science.gov (United States)

Tuzhilkin, D. A.; Borodin, A. S.

2017-11-01

The results of the study of variations in the electromagnetic background parameters of the Schumann resonator frequency range and the variability indices of the human heart period during its free activity are presented on the basis of 24-hour synchronous monitoring data. It is shown that the integral evaluation of the conjugacy of the heart rate variability indices from the Schumann resonance parameters is extremely weak. In this case, the differential evaluation of this dependence with separation into characteristic time intervals of the day, characterized by different motor activity of the subjects, becomes significantly higher. The number of volunteers whose conjugacy is characterized by a strong correlation in some cases reaches 35 percent of the sample.

Comparison of global storm activity rate calculated from Schumann resonance background components to electric field intensity E0 Z

Science.gov (United States)

Nieckarz, Zenon; Kułak, Andrzej; Zięba, Stanisław; Kubicki, Marek; Michnowski, Stanisław; Barański, Piotr

2009-02-01

This work presents the results of a comparison between the global storm activity rate IRS and electric field intensity E0 Z. The permanent analysis of the IRS may become an important tool for testing Global Electric Circuit models. IRS is determined by a new method that uses the background component of the first 7 Schumann resonances (SR). The rate calculations are based on ELF observations carried out in 2005 and 2006 in the observatory station "Hylaty" of the Jagiellonian University in the Eastern Carpathians (Kułak, A., Zięba, S., Micek, S., Nieckarz, Z., 2003. Solar variations in extremely low frequency propagation parameters: I. A two-dimensional telegraph equation (TDTE) model of ELF propagation and fundamental parameters of Schumann resonances, J. Geophys. Res., 108, 1270, doi:10.1029/2002JA009304). Diurnal runs of the IRS rate were compared with diurnal runs of E0 Z amplitudes registered at the Earth's surface in the Geophysical Observatory of the Polish Academy of Sciences in Świder (Kubicki, M., 2005. Results of Atmospheric Electricity and Meteorological Observations, S. Kalinowski Geophysical Observatory at Świder 2004, Pub. Inst. Geophysics Polish Academy of Sciences, D-68 (383), Warszawa.). The days with the highest values of the correlation coefficient ( R) between amplitudes of both observed parameters characterizing atmosphere electric activity are shown. The seasonal changes of R, IRS and E0 Z are also presented.

Numerical Simulation of the Variation of Schumann Resonance Associated with Seismogenic Processe in the Lithosphere-Atmosphere-Ionosphere system

Science.gov (United States)

Liu, L.; Huang, Q.; Wang, Y.

2012-12-01

The variations in the strength and frequency shift of the Schumann resonance (SR) of the electromagnetic (EM) field prior to some significance earthquakes were reported by a number of researchers. As a robust physical phenomenon constantly exists in the resonant cavity formed by the lithosphere-atmosphere-ionosphere system, irregular variations in SR parameters can be naturally attributed to be the potential precursory observables for forecasting earthquake occurrences. Schumann resonance (SR) of the EM field between the lithosphere and the ionosphere occurs because the space between the surface of the Earth and the conductive ionosphere acts as a closed waveguide. The cavity is naturally excited by electric currents generated by lightning. SR is the principal background in the electromagnetic spectrum at extremely low frequencies (ELF) between 3-69 Hz. We simulated the EM field in the lithosphere-ionosphere waveguide with a 2-dimensional (2D), cylindrical whole-earth model by the hybrid pseudo-spectral and finite difference time domain method. Considering the seismogensis as a fully coupled seismoelectric process, we simulate the seismic wave and EM wave in this 2D model. The excitation of SR in the background EM field are generated by the electric-current impulses due to lightning thunderstorms within the lowest 10 kilometers of the atmosphere . The diurnal variation and the latitude-dependence in ion concentration in the ionosphere are included in the model. After the SR has reached the steady state, the impulse generated by the seismogenic process (pre-, co- and post-seismic) in the crust is introduced to assess the possible precursory effects on SR strength and frequency. The modeling results explain the observed fact of why SR has a much more sensitive response to continental earthquakes, and much less response to oceanic events; the reason is simply due to the shielding effect of the conductive ocean that prevents effective radiation of the seismoelectric

Investigation of Global Lightning using Schumann Resonances measured by High Frequency Induction Coil Magnetometers in the UK

Science.gov (United States)

Beggan, C.; Gabillard, T.; Swan, A.; Flower, S. M.; Thomson, A. W.

2012-12-01

In June 2012, the British Geological Survey Geomagnetism team installed two high frequency (100 Hz) induction coil magnetometers at the Eskdalemuir Observatory, in the Scottish Borders of the United Kingdom. The induction coils permit us to measure the very rapid changes of the magnetic field. The Eskdalemuir Observatory is one of the longest running geophysical sites in the UK (beginning operation in 1904) and is located in a rural valley with a quiet magnetic environment. The data output from the induction coils are digitized and logged onsite before being collected once per hour and sent to the Edinburgh office via the Internet. We intend to run the coils as a long term experiment. We present initial results from first five months of data. Analysis of spectrograms and power spectral density plots in the frequency band of 3-40 Hz from the coils show diffuse bands of peak power around 7.8 Hz, 14.3 Hz, 20.8 Hz, 27 Hz, 34 Hz and 39Hz related to the global Schumann resonances. We also detect a strong narrow peak at 25 Hz, which is a harmonic of the UK electrical power system. There are a number of features in the data that we wish to investigate, including the diurnal and seasonal variation of the Schumann resonances. For example, it has been suggested that lightning activity is related to climate variability in the tropics and that perhaps Madden-Julian Oscillations (MJO) or El Niño Southern Oscillation (ENSO)-like correlations are detectable within the data. On longer timescales, we will look for solar cycle and climate variations. We also wish to note that the data is freely available on request to the community.

Aliasing of the Schumann resonance background signal by sprite-associated Q-bursts

Science.gov (United States)

Guha, Anirban; Williams, Earle; Boldi, Robert; Sátori, Gabriella; Nagy, Tamás; Bór, József; Montanyà, Joan; Ortega, Pascal

2017-12-01

The Earth's naturally occurring Schumann resonances (SR) are composed of a quasi-continuous background component and a larger-amplitude, short-duration transient component, otherwise called 'Q-burst' (Ogawa et al., 1967). Sprites in the mesosphere are also known to accompany the energetic positive ground flashes that launch the Q-bursts (Boccippio et al., 1995). Spectra of the background Schumann Resonances (SR) require a natural stabilization period of ∼10-12 min for the three conspicuous modal parameters to be derived from Lorentzian fitting. Before the spectra are computed and the fitting process is initiated, the raw time series data need to be properly filtered for local cultural noise, narrow band interference as well as for large transients in the form of global Q-bursts. Mushtak and Williams (2009) describe an effective technique called Isolated Lorentzian (I-LOR), in which, the contributions from local cultural and various other noises are minimized to a great extent. An automated technique based on median filtering of time series data has been developed. These special lightning flashes are known to have greater contribution in the ELF range (below 1 kHz) compared to general negative CG strikes (Huang et al., 1999; Cummer et al., 2006). The global distributions of these Q-bursts have been studied by Huang et al. (1999) Rhode Island, USA by wave impedance methods from single station ELF measurements at Rhode Island, USA and from Japan Hobara et al. (2006). The present work aims to demonstrate the effect of Q-bursts on SR background spectra using GPS time-stamped observation of TLEs. It is observed that the Q-bursts selected for the present work do alias the background spectra over a 5-s period, though the amplitudes of these Q-bursts are far below the background threshold of 16 Core Standard Deviation (CSD) so that they do not strongly alias the background spectra of 10-12 min duration. The examination of one exceptional Q-burst shows that appreciable

Determination of the Global-Average Charge Moment of a Lightning Flash Using Schumann Resonances and the LIS/OTD Lightning Data

Science.gov (United States)

Boldi, Robert; Williams, Earle; Guha, Anirban

2018-01-01

In this paper, we use (1) the 20 year record of Schumann resonance (SR) signals measured at West Greenwich Rhode Island, USA, (2) the 19 year Lightning Imaging Sensor (LIS)/Optical Transient Detector (OTD) lightning data, and (3) the normal mode equations for a uniform cavity model to quantify the relationship between the observed Schumann resonance modal intensity and the global-average vertical charge moment change M (C km) per lightning flash. This work, by integrating SR measurements with satellite-based optical measurements of global flash rate, accomplishes this quantification for the first time. To do this, we first fit the intensity spectra of the observed SR signals to an eight-mode, three parameter per mode, (symmetric) Lorentzian line shape model. Next, using the LIS/OTD lightning data and the normal mode equations for a uniform cavity model, we computed the expected climatological-daily-average intensity spectra. We then regressed the observed modal intensity values against the expected modal intensity values to find the best fit value of the global-average vertical charge moment change of a lightning flash (M) to be 41 C km per flash with a 99% confidence interval of ±3.9 C km per flash, independent of mode. Mode independence argues that the model adequately captured the modal intensity, the most important fit parameter herein considered. We also tested this relationship for the presence of residual modal intensity at zero lightning flashes per second and found no evidence that modal intensity is significantly different than zero at zero lightning flashes per second, setting an upper limit to the amount of nonlightning contributions to the observed modal intensity.

Analysis of plasma equilibrium based on orbit-driven current density profile in steady-state plasma on QUEST

Energy Technology Data Exchange (ETDEWEB)

Nakamura, K., E-mail: nakamura@triam.kyushu-u.ac.jp [RIAM, Kyushu University, Kasuga 816-8580 (Japan); Alam, M.M. [IGSES, Kyushu University, Kasuga 816-8580 (Japan); Jiang, Y.Z. [Tsinghua University, Beijing 100084 (China); Mitarai, O. [Tokai University, Kumamoto 862-8652 (Japan); Kurihara, K.; Kawamata, Y.; Sueoka, M.; Takechi, M. [Japan Atomic Energy Agency, Naka 311-0193 (Japan); Hasegawa, M.; Tokunaga, K.; Araki, K.; Zushi, H.; Hanada, K.; Fujisawa, A.; Idei, H.; Nagashima, Y.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Nagata, T. [RIAM, Kyushu University, Kasuga 816-8580 (Japan); and others

2016-11-01

Highlights: • High energy particle guiding center orbit is calculated as a contour plot of conserved variable. • Current density profile is analyzed based on the orbit-driven current. • Plasma equilibrium is reconstructed by considering the hollow current profile. - Abstract: In the present RF-driven (ECCD) steady-state plasma on QUEST (B{sub t} = 0.25 T, R = 0.68 m, a = 0.40 m), plasma current seems to flow in the open magnetic surface outside of the closed magnetic surface in the low-field region according to plasma current fitting (PCF) method. We consider that the current in the open magnetic surface is due to orbit-driven current by high-energy particles in RF-driven plasma. So based on the analysis of current density profile based on the orbit-driven current, plasma equilibrium is to be calculated. We calculated high energy particles guiding center orbits as a contour plot of conserved variable in Hamiltonian formulation and considered particles initial position with different levels of energy and pitch angles that satisfy resonance condition. Then the profile of orbit-driven current is estimated by multiplying the particle density on the resonance surface and the velocity on the orbits. This analysis shows negative current near the magnetic axis and hollow current profile is expected even if pressure driven current is considered. Considering the hollow current profile shifted toward the low-field region, the equilibrium is fitted by J-EFIT coded by MATLAB.

Wave-driven countercurrent plasma centrifuge

Energy Technology Data Exchange (ETDEWEB)

Fetterman, Abraham J; Fisch, Nathaniel J [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08540 (United States)

2009-11-15

A method for driving rotation and a countercurrent flow in a fully ionized plasma centrifuge is described. The rotation is produced by radiofrequency waves near the cyclotron resonance. The wave energy is transferred into potential energy in a manner similar to the {alpha} channeling effect. The countercurrent flow may also be driven by radiofrequency waves. By driving both the rotation and the flow pattern using waves instead of electrodes, physical and engineering issues may be avoided.

Wave-driven countercurrent plasma centrifuge

International Nuclear Information System (INIS)

Fetterman, Abraham J; Fisch, Nathaniel J

2009-01-01

A method for driving rotation and a countercurrent flow in a fully ionized plasma centrifuge is described. The rotation is produced by radiofrequency waves near the cyclotron resonance. The wave energy is transferred into potential energy in a manner similar to the α channeling effect. The countercurrent flow may also be driven by radiofrequency waves. By driving both the rotation and the flow pattern using waves instead of electrodes, physical and engineering issues may be avoided.

Wave-driven Countercurrent Plasma Centrifuge

International Nuclear Information System (INIS)

Fetterman, A.J.; Fisch, N.J.

2009-01-01

A method for driving rotation and a countercurrent flow in a fully ionized plasma centrifuge is described. The rotation is produced by radiofrequency waves near the cyclotron resonance. The wave energy is transferred into potential energy in a manner similar to the α channeling effect. The countercurrent flow may also be driven by radiofrequency waves. By driving both the rotation and the flow pattern using waves instead of electrodes, physical and engineering issues may be avoided

Peculiar transient events in the Schumann resonance band and their possible explanation

Science.gov (United States)

Ondrásková, Adriena; Bór, József; S[Breve]Evcík, Sebastián; Kostecký, Pavel; Rosenberg, Ladislav

2008-04-01

Superimposed on the continuous Schumann resonance (SR) background in the extremely low frequency (ELF) band, transient signals (e.g. bursts) can be observed, which originate from intense lightning discharges occurring at different locations on the globe. From the many transients that were observed at the Astronomical and Geophysical Observatory (AGO) of Comenius University near Modra, western Slovakia, in the vertical electric field component mainly during May and June of 2006, a peculiar group of events could be recognized. According to the waveform analysis, these peculiar events in most cases consist of two overlapping transients with a characteristic time difference of 0.13-0.15 s between the onsets. On the other hand, the spectrum of these peculiar transients showed discernible SR peaks for higher modes as well (n>7). The same events could be found in the records of the Széchenyi István Geophysical Observatory of the Geodetic and Geophysical Research Institute of the Hungarian Academy of Sciences near Nagycenk, Hungary (NCK). The natural origin of the peculiar events was verified from the NCK data and the source location was determined from the second transient. The results suggest that the two consecutive transients originated in the same thunderstorm. Furthermore, the phase spectrum analysis indicates that the sources have coherently excited the Earth-ionosphere cavity. These findings seem to support the idea that electromagnetic waves orbiting the Earth might trigger lightning discharges. The possibility that electromagnetic waves may trigger discharges was first considered by Nikola Tesla.

Pianist Jeanne Schumann to perform

OpenAIRE

Crichton, Juliet B.

2005-01-01

Award-winning pianist Jeanne Schumann will present the Marilyn Norstedt Memorial Concert at 7:30 p.m. Saturday, April 2, in the Squires Recital Salon on Virginia Tech's campus. The concert is sponsored by Musica Viva! of Southwest Virginia and the Virginia Tech University Libraries.

Self-consistent modeling of induced magnetic field in Titan's atmosphere accounting for the generation of Schumann resonance

Science.gov (United States)

Béghin, Christian

2015-02-01

This model is worked out in the frame of physical mechanisms proposed in previous studies accounting for the generation and the observation of an atypical Schumann Resonance (SR) during the descent of the Huygens Probe in the Titan's atmosphere on 14 January 2005. While Titan is staying inside the subsonic co-rotating magnetosphere of Saturn, a secondary magnetic field carrying an Extremely Low Frequency (ELF) modulation is shown to be generated through ion-acoustic instabilities of the Pedersen current sheets induced at the interface region between the impacting magnetospheric plasma and Titan's ionosphere. The stronger induced magnetic field components are focused within field-aligned arcs-like structures hanging down the current sheets, with minimum amplitude of about 0.3 nT throughout the ramside hemisphere from the ionopause down to the Moon surface, including the icy crust and its interface with a conductive water ocean. The deep penetration of the modulated magnetic field in the atmosphere is thought to be allowed thanks to the force balance between the average temporal variations of thermal and magnetic pressures within the field-aligned arcs. However, there is a first cause of diffusion of the ELF magnetic components, probably due to feeding one, or eventually several SR eigenmodes. A second leakage source is ascribed to a system of eddy-Foucault currents assumed to be induced through the buried water ocean. The amplitude spectrum distribution of the induced ELF magnetic field components inside the SR cavity is found fully consistent with the measurements of the Huygens wave-field strength. Waiting for expected future in-situ exploration of Titan's lower atmosphere and the surface, the Huygens data are the only experimental means available to date for constraining the proposed model.

Investigations of Relatively Easy To Construct Antennas With Efficiency in Receiving Schumann Resonances: Preparations for a Miniaturized Reconfigurable ELF Receiver

Science.gov (United States)

Farmer, Brian W.; Hannan, Robert C.

2003-01-01

Relatively little is known about the cavity between the Earth and the ionosphere, which opens opportunities for technological advances and unique ideas. One effective means to study this cavity is with extremely low frequency (ELF) antennas. Possible applications of these antennas are global weather prediction, earthquake prediction, planetary exploration, communication, wireless transmission of power, or even a free energy source. The superconducting quantum interference device SQUID) and the coil antenna are the two most acceptable receivers discovered for picking up ELF magnetic fields. Both antennas have the potential for size reduction, allowing them to be portable enough for access to space and even for personal ware. With improvements of these antennas and signal processing, insightful analysis of Schumann resonance (SR) can give the science community a band of radio frequency (RF) signals for improving life here on Earth and exploring beyond.

Ion acceleration in non-equilibrium plasmas driven by fast drifting electron

Energy Technology Data Exchange (ETDEWEB)

Castro, G. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); Università degli Studi di Catania, Dipartimento di Fisica e Astronomia, V. S.Sofia 64, 95123 Catania (Italy); Di Bartolo, F., E-mail: fdibartolo@unime.it [Università di Messina, V.le F. Stagno D’Alcontres 31, 98166, Messina (Italy); Gambino, N. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); Università degli Studi di Catania, Dipartimento di Metodologie Fisiche e Chimiche per L’ingegneria, Viale A.Doria 6, 95125 Catania (Italy); Mascali, D. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); CSFNSM, Viale A. Doria 6, 95125 Catania (Italy); Romano, F.P. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); CNR-IBAM Via Biblioteca 4, 95124 Catania (Italy); Anzalone, A.; Celona, L.; Gammino, S. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); Di Giugno, R. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); Università degli Studi di Catania, Dipartimento di Fisica e Astronomia, V. S.Sofia 64, 95123 Catania (Italy); Lanaia, D. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); Miracoli, R. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); Università degli Studi di Catania, Dipartimento di Fisica e Astronomia, V. S.Sofia 64, 95123 Catania (Italy); Serafino, T. [CSFNSM, Viale A. Doria 6, 95125 Catania (Italy); Tudisco, S. [INFN- Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); CSFNSM, Viale A. Doria 6, 95125 Catania (Italy)

2013-05-01

We hereby present results on ion acceleration mechanisms in non equilibrium plasmas generated by microwaves or high intensity laser pulses. Experiments point out that in magnetized plasmas X–B conversion takes place for under resonance values of the magnetic field, i.e. an electromagnetic mode is converted into an electrostatic wave. The strong self-generated electric field, of the order of 10{sup 7} V/m, causes a E × B drift which accelerates both ions and electrons, as it is evident by localized sputtering in the plasma chamber. These fields are similar (in magnitude) to the ones obtainable in laser generated plasmas at intensity of 10{sup 12} W/cm{sup 2}. In this latter case, we observe that the acceleration mechanism is driven by electrons drifting much faster than plasma bulk, thus generating an extremely strong electric field ∼10{sup 7} V/m. The two experiments confirm that ions acceleration at low energy is possible with table-top devices and following complementary techniques: i.e. by using microwave-driven (producing CW beams) plasmas, or non-equilibrium laser-driven plasmas (producing pulsed beams). Possible applications involve ion implantation, materials surface modifications, ion beam assisted lithography, etc.

Experiments on resonator concept of plasma wakefield accelerator driven by a train of relativistic electron bunches

International Nuclear Information System (INIS)

Kiselev, V.A.; Linnik, A.F.; Mirny, V. I; Onishchenko, I.N.; Uskov, V.V.

2008-01-01

The experimental installation was elaborated to increase plasma wakefield amplitude by means of using plasma resonator that allows all bunches of the train to participate in wakefield build-up contrary to waveguide case, in which due to group velocity effect only a part of the bunches participates. Experiments on plasma producing with resonant density, at which a coincidence of the plasma frequency and bunch repetition frequency is provided, are carried out. The first results of the measurements of beam energy loss on plasma wakefield excitation and energy gain by accelerated electrons are presented

Current-driven turbulence in plasmas

International Nuclear Information System (INIS)

Kluiver, H. de.

1977-10-01

Research on plasma heating in linear and toroidal systems using current-driven turbulence is reviewed. The motivation for this research is presented. Relations between parameters describing the turbulent plasma state and macroscopic observables are given. Several linear and toroidal devices used in current-driven turbulence studies are described, followed by a discussion of special diagnostic methods used. Experimental results on the measurement of electron and ion heating, anomalous plasma conductivity and associated turbulent fluctuation spectra are reviewed. Theories on current-driven turbulence are discussed and compared with experiments. It is demonstrated from the experimental results that current-driven turbulence occurs not only for extreme values of the electric field but also for an experimentally much more accessible and wide range of parameters. This forms a basis for a discussion on possible future applications in fusion-oriented plasma research

Inversion of Multi-Station Schumann Resonance Background Records for Global Lightning Activity in Absolute Units

Science.gov (United States)

Williams, E. R.; Mushtak, V. C.; Guha, A.; Boldi, R. A.; Bor, J.; Nagy, T.; Satori, G.; Sinha, A. K.; Rawat, R.; Hobara, Y.; Sato, M.; Takahashi, Y.; Price, C. G.; Neska, M.; Alexander, K.; Yampolski, Y.; Moore, R. C.; Mitchell, M. F.; Fraser-Smith, A. C.

2014-12-01

Every lightning flash contributes energy to the TEM mode of the natural global waveguide that contains the Earth's Schumann resonances. The modest attenuation at ELF (0.1 dB/Mm) allows for the continuous monitoring of the global lightning with a small number of receiving stations worldwide. In this study, nine ELF receiving sites (in Antarctica (3 sites), Hungary, India, Japan, Poland, Spitsbergen and USA) are used to provide power spectra at 12-minute intervals in two absolutely calibrated magnetic fields and occasionally, one electric field, with up to five resonance modes each. The observables are the extracted modal parameters (peak intensity, peak frequency and Q-factor) for each spectrum. The unknown quantities are the geographical locations of three continental lightning 'chimneys' and their lightning source strengths in absolute units (C2 km2/sec). The unknowns are calculated from the observables by the iterative inversion of an evolving 'sensitivity matrix' whose elements are the partial derivatives of each observable for all receiving sites with respect to each unknown quantity. The propagation model includes the important day-night asymmetry of the natural waveguide. To overcome the problem of multiple minima (common in inversion problems of this kind), location information from the World Wide Lightning Location Network has been used to make initial guess solutions based on centroids of stroke locations in each chimney. Results for five consecutive days in 2009 (Jan 7-11) show UT variations with the African chimney dominating on four of five days, and America dominating on the fifth day. The amplitude variations in absolute source strength exceed that of the 'Carnegie curve' of the DC global circuit by roughly twofold. Day-to-day variations in chimney source strength are of the order of tens of percent. Examination of forward calculations performed with the global inversion solution often show good agreement with the observed diurnal variations at

Radial structure of curvature-driven instabilities in a hot-electron plasma

International Nuclear Information System (INIS)

Spong, D.A.; Berk, H.L.; Van Dam, J.W.

1984-01-01

A nonlocal analysis of curvature-driven instabilities for a hot-electron ring interacting with a warm background plasma has been made. Four different instability modes characteristic of hot-electron plasmas have been examined: the high-frequency hot-electron interchange (at frequencies larger than the ion-cyclotron frequency), the compressional Alfven instability, the interacting background pressure-driven interchange, and the conventional hot-electron interchange (at frequencies below the ion-cyclotron frequency). The decoupling condition between core and hot-electron plasmas has also been examined, and its influence on the background and hot-electron interchange stability boundaries has been studied. The assumed equilibrium plasma profiles and resulting radial mode structure differ somewhat from those used in previous local analytic estimates; however, when the analysis is calibrated to the appropriate effective radial wavelength of the nonlocal calculation, reasonable agreement is obtained. Comparison with recent experimental measurements indicates that certain of these modes may play a role in establishing operating boundaries for the ELMO Bumpy Torus-Scale (EBT-S) experiment. The calculations given here indicate the necessity of having core plasma outside the ring to prevent the destabilizing wave resonance of the precessional mode with a cold plasma

Self-resonant wakefield excitation by intense laser pulse in plasmas

International Nuclear Information System (INIS)

Andreev, N.E.; Pogosova, A.A.; Gorbunov, L.M.; Ramazashvili, R.R.; Kirsanov, V.I.

1993-01-01

It is demonstrated by theoretical analysis and numerical calculations that in an underdense plasma the process of three-dimensional evolution of the short and strong laser pulse (with duration equal to several plasma periods) leads to compression and self-modulation of the pulse, so that during a fairly long period of time beats of pulse amplitude generates resonantly a strong and stable plasma wakefield. The intensity of the wake-field is so high that it can provide a new promising outlook for the plasma based accelerator concept. Linear analysis of dispersion relation predicts that taking into account transverse component of wavenumber considerably increases the growth rate of resonance instability of the pulse. The numerical simulations demonstrate that considered self-focusing and resonant-modulation instability are essentially three dimensional processes. Laser field evolution in each transverse cross section of the pulse is synchronized by the regular structure of plasma wave that is excited by the pulse. The considered effect of resonant modulation has a threshold. For the pulses with the intensity below the threshold the refraction dominates and no modulation appears. The studied phenomenon can be referred to as the Self-Resonant Wakefield (SRWF) excitation that is driven by self-focusing and self-modulation of laser pulse with quite a moderate initial duration. In fact, this method of excitation differs from both suggested in Ref.1 (PBWA) and in Refs.2,3 (LWFA), being even more than the combination of these concepts. Unlike the first scheme it does not require initially the two-frequency laser pulse, since the modulation here appears in the most natural way due to evolution of the pulse. In contrast with the LWFA, the considered SRWF generation scheme gives the possibility to raise the intensity of wake-excitation due to pulse self-focusing ( initial stage) and self modulation (second stage)

Plasma production for electron acceleration by resonant plasma wave

International Nuclear Information System (INIS)

Anania, M.P.; Biagioni, A.; Chiadroni, E.; Cianchi, A.; Croia, M.; Curcio, A.; Di Giovenale, D.; Di Pirro, G.P.; Filippi, F.; Ghigo, A.; Lollo, V.; Pella, S.; Pompili, R.; Romeo, S.; Ferrario, M.

2016-01-01

Plasma wakefield acceleration is the most promising acceleration technique known nowadays, able to provide very high accelerating fields (10–100 GV/m), enabling acceleration of electrons to GeV energy in few centimeter. However, the quality of the electron bunches accelerated with this technique is still not comparable with that of conventional accelerators (large energy spread, low repetition rate, and large emittance); radiofrequency-based accelerators, in fact, are limited in accelerating field (10–100 MV/m) requiring therefore hundred of meters of distances to reach the GeV energies, but can provide very bright electron bunches. To combine high brightness electron bunches from conventional accelerators and high accelerating fields reachable with plasmas could be a good compromise allowing to further accelerate high brightness electron bunches coming from LINAC while preserving electron beam quality. Following the idea of plasma wave resonant excitation driven by a train of short bunches, we have started to study the requirements in terms of plasma for SPARC-LAB (Ferrario et al., 2013 [1]). In particular here we focus on hydrogen plasma discharge, and in particular on the theoretical and numerical estimates of the ionization process which are very useful to design the discharge circuit and to evaluate the current needed to be supplied to the gas in order to have full ionization. Eventually, the current supplied to the gas simulated will be compared to that measured experimentally.

Plasma production for electron acceleration by resonant plasma wave

Energy Technology Data Exchange (ETDEWEB)

Anania, M.P., E-mail: maria.pia.anania@lnf.infn.it [INFN - LNF, via Enrico Fermi, 40, 00044 Frascati (Italy); Biagioni, A.; Chiadroni, E. [INFN - LNF, via Enrico Fermi, 40, 00044 Frascati (Italy); Cianchi, A. [University of Rome Tor Vergata - INFN, via della Ricerca Scientifica, 1, 00133 Roma (Italy); INFN, Via della Ricerca Scientifica, 1, 00133 Roma (Italy); Croia, M.; Curcio, A. [INFN - LNF, via Enrico Fermi, 40, 00044 Frascati (Italy); University of Rome La Sapienza, Piazzale Aldo Moro, 2, 00185 Roma (Italy); Di Giovenale, D.; Di Pirro, G.P. [INFN - LNF, via Enrico Fermi, 40, 00044 Frascati (Italy); Filippi, F. [University of Rome La Sapienza, Piazzale Aldo Moro, 2, 00185 Roma (Italy); Ghigo, A.; Lollo, V.; Pella, S.; Pompili, R. [INFN - LNF, via Enrico Fermi, 40, 00044 Frascati (Italy); Romeo, S. [INFN - LNF, via Enrico Fermi, 40, 00044 Frascati (Italy); University of Rome La Sapienza, Piazzale Aldo Moro, 2, 00185 Roma (Italy); Ferrario, M. [INFN - LNF, via Enrico Fermi, 40, 00044 Frascati (Italy)

2016-09-01

Plasma wakefield acceleration is the most promising acceleration technique known nowadays, able to provide very high accelerating fields (10–100 GV/m), enabling acceleration of electrons to GeV energy in few centimeter. However, the quality of the electron bunches accelerated with this technique is still not comparable with that of conventional accelerators (large energy spread, low repetition rate, and large emittance); radiofrequency-based accelerators, in fact, are limited in accelerating field (10–100 MV/m) requiring therefore hundred of meters of distances to reach the GeV energies, but can provide very bright electron bunches. To combine high brightness electron bunches from conventional accelerators and high accelerating fields reachable with plasmas could be a good compromise allowing to further accelerate high brightness electron bunches coming from LINAC while preserving electron beam quality. Following the idea of plasma wave resonant excitation driven by a train of short bunches, we have started to study the requirements in terms of plasma for SPARC-LAB (Ferrario et al., 2013 [1]). In particular here we focus on hydrogen plasma discharge, and in particular on the theoretical and numerical estimates of the ionization process which are very useful to design the discharge circuit and to evaluate the current needed to be supplied to the gas in order to have full ionization. Eventually, the current supplied to the gas simulated will be compared to that measured experimentally.

Poloidal rotation driven by electron cyclotron resonance wave in tokamak plasmas

Directory of Open Access Journals (Sweden)

Qing Zhou

2017-10-01

Full Text Available The poloidal electric filed, which is the drive field of poloidal rotation, has been observed and increases obviously after the injection of electron cyclotron resonance wave in HL-2A experiment, and the amplitude of the poloidal electric field is in the order of 103 V/m. Through theoretical analysis using Stringer rotation model, the observed poloidal electric field is of the same order as the theoretical calculation value. In addition, the magnetic pump damping which would damp the poloidal rotation is calculated numerically and the calculation results show that the closer to the core plasmas, the stronger the magnetic pump damping will be. Meanwhile, according to the value of the calculated magnetic pump damping, the threshold of the poloidal electric field which could overcome magnetic pump damping and drive poloidal rotation in tokamak plasmas is given out. Finally, the poloidal rotation velocity over time at different minor radius is studied theoretically.

Electron heating via self-excited plasma series resonance in geometrically symmetric multi-frequency capacitive plasmas

International Nuclear Information System (INIS)

Schüngel, E; Brandt, S; Schulze, J; Donkó, Z; Korolov, I; Derzsi, A

2015-01-01

The self-excitation of plasma series resonance (PSR) oscillations plays an important role in the electron heating dynamics in capacitively coupled radio-frequency (CCRF) plasmas. In a combined approach of PIC/MCC simulations and a theoretical model based on an equivalent circuit, we investigate the self-excitation of PSR oscillations and their effect on the electron heating in geometrically symmetric CCRF plasmas driven by multiple consecutive harmonics. The discharge symmetry is controlled via the electrical asymmetry effect (EAE), i.e. by varying the total number of harmonics and tuning the phase shifts between them. It is demonstrated that PSR oscillations will be self-excited under both symmetric and asymmetric conditions, if (i) the charge–voltage relation of the plasma sheaths deviates from a simple quadratic behavior and (ii) the inductance of the plasma bulk exhibits a temporal modulation. These two effects have been neglected up to now, but we show that they must be included in the model in order to properly describe the nonlinear series resonance circuit and reproduce the self-excitation of PSR oscillations, which are observed in the electron current density resulting from simulations of geometrically symmetric CCRF plasmas. Furthermore, the effect of PSR self-excitation on the discharge current and the plasma properties, such as the potential profile, is illustrated by applying Fourier analysis. High-frequency oscillations in the entire spectrum between the applied frequencies and the local electron plasma frequency are observed. As a consequence, the electron heating is strongly enhanced by the presence of PSR oscillations. A complex electron heating dynamics is found during the expansion phase of the sheath, which is fully collapsed, when the PSR is initially self-excited. The nonlinear electron resonance heating (NERH) associated with the PSR oscillations causes a spatial asymmetry in the electron heating. By discussing the resulting ionization

Resonances in a periodically driven bosonic system

Science.gov (United States)

Quelle, Anton; Smith, Cristiane Morais

2017-11-01

Periodically driven systems are a common topic in modern physics. In optical lattices specifically, driving is at the origin of many interesting phenomena. However, energy is not conserved in driven systems, and under periodic driving, heating of a system is a real concern. In an effort to better understand this phenomenon, the heating of single-band systems has been studied, with a focus on disorder- and interaction-induced effects, such as many-body localization. Nevertheless, driven systems occur in a much wider context than this, leaving room for further research. Here, we fill this gap by studying a noninteracting model, characterized by discrete, periodically spaced energy levels that are unbounded from above. We couple these energy levels resonantly through a periodic drive, and discuss the heating dynamics of this system as a function of the driving protocol. In this way, we show that a combination of stimulated emission and absorption causes the presence of resonant stable states. This will serve to elucidate the conditions under which resonant driving causes heating in quantum systems.

Resonances in a periodically driven bosonic system.

Science.gov (United States)

Quelle, Anton; Smith, Cristiane Morais

2017-11-01

Periodically driven systems are a common topic in modern physics. In optical lattices specifically, driving is at the origin of many interesting phenomena. However, energy is not conserved in driven systems, and under periodic driving, heating of a system is a real concern. In an effort to better understand this phenomenon, the heating of single-band systems has been studied, with a focus on disorder- and interaction-induced effects, such as many-body localization. Nevertheless, driven systems occur in a much wider context than this, leaving room for further research. Here, we fill this gap by studying a noninteracting model, characterized by discrete, periodically spaced energy levels that are unbounded from above. We couple these energy levels resonantly through a periodic drive, and discuss the heating dynamics of this system as a function of the driving protocol. In this way, we show that a combination of stimulated emission and absorption causes the presence of resonant stable states. This will serve to elucidate the conditions under which resonant driving causes heating in quantum systems.

Theoretical approach for plasma series resonance effect in geometrically symmetric dual radio frequency plasma

International Nuclear Information System (INIS)

Bora, B.; Bhuyan, H.; Favre, M.; Wyndham, E.; Chuaqui, H.

2012-01-01

Plasma series resonance (PSR) effect is well known in geometrically asymmetric capacitively couple radio frequency plasma. However, plasma series resonance effect in geometrically symmetric plasma has not been properly investigated. In this work, a theoretical approach is made to investigate the plasma series resonance effect and its influence on Ohmic and stochastic heating in geometrically symmetric discharge. Electrical asymmetry effect by means of dual frequency voltage waveform is applied to excite the plasma series resonance. The results show considerable variation in heating with phase difference between the voltage waveforms, which may be applicable in controlling the plasma parameters in such plasma.

Screening Resonances In Plasmas

International Nuclear Information System (INIS)

Winkler, P.

1998-01-01

When it was suggested that a new recombination mechanism (Resonant Radiative Recombination (RRR)) which, based on very general physical arguments, should happen in dense plasmas and promises to provide useful information for the local temperature and density diagnostics of plasmas, they assumed the existence of screening resonances. For model potentials the existence of screening resonances has been demonstrated beyond reasonable doubt in a number of calculations. The key question, how well those potentials describe the dominant effects of a real plasma remains open. The relation of theoretical predictions to experimentally measurable effects is an important issue at the present stage of their research. In particular, RRR is expected to account for enhanced recombination rates of low energetic electrons with their ions, since the first stage is the resonant capture of a slow electron by an atom or ion. The mechanism that traps an electron is a combination of complicated many-body interactions of the ions and electrons. For clarity they start here, however, with a discussion in terms of local potential traps the shapes of which are determined predominantly and in an average way by two factors: the degree of screening present at the ionic site and the degree of short-range order in the immediate neighborhood of this ion

Magnetically driven oscillator and resonance: a teaching tool

Science.gov (United States)

Erol, M.; Çolak, İ. Ö.

2018-05-01

This paper reports a simple magnetically driven oscillator, designed and resolved in order to achieve a better student understanding and to overcome certain instructional difficulties. The apparatus is mainly comprised of an ordinary spring pendulum with a neodymium magnet attached to the bottom, a coil placed in the same vertical direction, an ordinary function generator, an oscilloscope and a smartphone. Driven oscillation and resonance is basically managed by applying a sinusoidal voltage to the coil and tuning the driving frequency to the natural frequency of the pendulum. The resultant oscillation is recorded by a smartphone video application and analyzed via a video analysis programme. The designed apparatus can easily be employed in basic physics laboratories to achieve an enhanced and deeper understanding of driven oscillation and resonance.

Parametric instabilities in resonantly-driven Bose–Einstein condensates

Science.gov (United States)

Lellouch, S.; Goldman, N.

2018-04-01

Shaking optical lattices in a resonant manner offers an efficient and versatile method to devise artificial gauge fields and topological band structures for ultracold atomic gases. This was recently demonstrated through the experimental realization of the Harper–Hofstadter model, which combined optical superlattices and resonant time-modulations. Adding inter-particle interactions to these engineered band systems is expected to lead to strongly-correlated states with topological features, such as fractional Chern insulators. However, the interplay between interactions and external time-periodic drives typically triggers violent instabilities and uncontrollable heating, hence potentially ruling out the possibility of accessing such intriguing states of matter in experiments. In this work, we study the early-stage parametric instabilities that occur in systems of resonantly-driven Bose–Einstein condensates in optical lattices. We apply and extend an approach based on Bogoliubov theory (Lellouch et al 2017 Phys. Rev. X 7 021015) to a variety of resonantly-driven band models, from a simple shaken Wannier–Stark ladder to the more intriguing driven-induced Harper–Hofstadter model. In particular, we provide ab initio numerical and analytical predictions for the stability properties of these topical models. This work sheds light on general features that could guide current experiments to stable regimes of operation.

Proton-driven Plasma Wakefield Acceleration

CERN Multimedia

CERN. Geneva

2012-01-01

The construction of ever larger and costlier accelerator facilities has a limited future, and new technologies will be needed to push the energy frontier. Plasma wakefield acceleration is a rapidly developing field and is a promising candidate technology for future high energy colliders. We focus on the recently proposed idea of proton-driven plasma wakefield acceleration and describe the current status and plans for this approach.

Josephson plasma resonance in superconducting multilayers

DEFF Research Database (Denmark)

Pedersen, Niels Falsig

1999-01-01

We derive an analytical solution for the josephson plasma resonance of superconducting multilayers. This analytical solution is derived mainly for low T-c systems with magnetic coupling between the superconducting layers, but many features of our results are more general, and thus an application...... to the recently derived plasma resonance phenomena for high T-c superconductors of the BSCCO type is discussed....

Pressure-driven amplification and penetration of resonant magnetic perturbations

Energy Technology Data Exchange (ETDEWEB)

Loizu, J. [Max-Planck-Institut für Plasmaphysik, D-17491 Greifswald (Germany); Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States); Hudson, S. R.; Lazerson, S. A.; Bhattacharjee, A. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States); Helander, P. [Max-Planck-Institut für Plasmaphysik, D-17491 Greifswald (Germany)

2016-05-15

We show that a resonant magnetic perturbation applied to the boundary of an ideal plasma screw-pinch equilibrium with nested surfaces can penetrate inside the resonant surface and into the core. The response is significantly amplified with increasing plasma pressure. We present a rigorous verification of nonlinear equilibrium codes against linear theory, showing excellent agreement.

Progress of Laser-Driven Plasma Accelerators

International Nuclear Information System (INIS)

Nakajima, Kazuhisa

2007-01-01

There is a great interest worldwide in plasma accelerators driven by ultra-intense lasers which make it possible to generate ultra-high gradient acceleration and high quality particle beams in a much more compact size compared with conventional accelerators. A frontier research on laser and plasma accelerators is focused on high energy electron acceleration and ultra-short X-ray and Tera Hertz radiations as their applications. These achievements will provide not only a wide range of sciences with benefits of a table-top accelerator but also a basic science with a tool of ultrahigh energy accelerators probing an unknown extremely microscopic world.Harnessing the recent advance of ultra-intense ultra-short pulse lasers, the worldwide research has made a tremendous breakthrough in demonstrating high-energy high-quality particle beams in a compact scale, so called ''dream beams on a table top'', which represents monoenergetic electron beams from laser wakefield accelerators and GeV acceleration by capillary plasma-channel laser wakefield accelerators. This lecture reviews recent progress of results on laser-driven plasma based accelerator experiments to quest for particle acceleration physics in intense laser-plasma interactions and to present new outlook for the GeV-range high-energy laser plasma accelerators

Synchro-betatron resonances driven by the beam-beam interaction

International Nuclear Information System (INIS)

Furman, M.A.

1994-01-01

We present a selective summary of the discussions on beam-beam-driven synchrobetatron resonances at the 6th Advanced ICFA Beam Dynamics Workshop on the subject ''Synchro-Betatron Resonances,'' held in Funchal (Madeira, Portugal), October 24--30, 1993

The numerical simulation of plasma flow in cylindrical resonant cavity of microwave plasma thruster

International Nuclear Information System (INIS)

Tang, J.-L.; He, H.-Q; Mao, G.-W.

2004-01-01

Microwave Plasma Thruster (MPT) is an electro-thermal propulsive device. MPT consists of microwave generator, gas storing and supplying system, resonant cavity and accelerative nozzle. It generates free-floating plasma brought by the microwave discharge breakdown gas in the resonant cavity, and the plasma exhausted from nozzle produces thrust. MPT has prospective application in spacecraft because of its advantages of high thrust, moderate specific impulse and high efficiency. In this paper, the numerical simulation of the coupling flow field of microwave plasma in resonant cavity under different frequencies will be discussed. The results of numerical simulation are as follows: 1) When the resonant model TM 011 was used, the higher the microwave frequency was, the smaller the size of MPT. The distribution of the electromagnetic field in small cavity, however, remain unchanged. 2) When the resonant model was used, the distribution of the temperature, the pressure and the electronic density in the resonant cavity remained unchanged under different resonant frequencies. 3) When the resonant frequency was increased with a fixed pressure distribution in a small cavity, compare to the MPT with lower frequency, the gas flow rate, the microwave power and the nozzle throat diameter of MPT all decreased. 4) The electromagnetic field in the cylindrical resonant cavity for all MPT with different frequencies was disturbed by the plasma formation. The strong disturbance happened in the region close to the plasma. (author)

Power line emission 50/60 Hz and Schumann resonances observed by microsatellite Chibis-M in the Earth's ionosphere

Science.gov (United States)

Dudkin, Denys; Pilipenko, Vyacheslav; Dudkin, Fedir; Pronenko, Vira; Klimov, Stanislav

2015-04-01

The overhead power lines are the sources of intense wideband electromagnetic (EM) emission, especially in ELF-VLF range, because of significant length (up to a few thousand kilometers) and strong 50/60 Hz currents with noticeable distortion. The radiation efficiency of the power line emission (PLE) increases with the harmonic order, so they are well observed by ground-based EM sensors. However their observations by low orbiting satellites (LEO) are very rare, particularly at basic harmonic 50/60 Hz, because of the ionospheric plasma opacity in ELF band. The Schumann resonance (SR) is the narrow-band EM noise that occurs due to the global thunderstorm activity in the Earth-ionosphere cavity. The first five eigenmodes of the SR are 7.8, 14.3, 20.8, 27.3 and 33.8 Hz and, thus, SR harmonics are also strongly absorbed by the Earth ionosphere. The published numerical simulations show that the penetration depth of such an ELF emission into the Earth's ionosphere is limited to 50-70 km for electric field and 120-240 km for magnetic field. From this follows, that PLE and SR can hardly ever be detected by LEO satellites, i.e. above the F-layer of ionosphere. In spite of this fact, these emissions were recently observed with use of the electric field antennas placed on the satellites C/NOFS (USA) and Chibis-M (Russia). Microsatellite Chibis-M was launched on January 24, 2012, at 23:18:30 UTC from the cargo ship "Progress M-13M" to circular orbit with altitude ~500 km and inclination ~52° . Chibis-M mass is about 40 kg where one third is a scientific instrumentation. The dimensions of the microsatellite case are 0.26x0.26x0.54 m with the outside mounted solar panels, service and scientific instrumentation. The main scientific objective of Chibis-M is the theoretical model verification for the atmospheric gamma-ray bursts. It requires the study of the accompanying EM processes such as the plasma waves produced by the lightning discharges in the VLF band. Chibis-M decayed on 15

Longitudinally mounted light emitting plasma in a dielectric resonator

Energy Technology Data Exchange (ETDEWEB)

Gilliard, Richard; DeVincentis, Marc; Hafidi, Abdeslam; O' Hare, Daniel; Hollingsworth, Gregg [LUXIM Corporation, 1171 Borregas Avenue, Sunnyvale, CA 94089 (United States)

2011-06-08

Methods for coupling power from a dielectric resonator to a light-emitting plasma have been previously described (Gilliard et al IEEE Trans. Plasma Sci. at press). Inevitably, regardless of the efficiency of power transfer, much of the emitted light is absorbed in the resonator itself which physically surrounds much if not all of the radiating material. An investigation into a method is presented here for efficiently coupling power to a longitudinally mounted plasma vessel which is mounted on the surface of the dielectric material of the resonator, thereby eliminating significant absorption of light within the resonator structure. The topology of the resonator and its physical properties as well as those of the metal halide plasma are presented. Results of basic models of the field configuration and plasma are shown as well as a configuration suitable as a practical light source.

Electron waves and resonances in bounded plasmas

CERN Document Server

Vandenplas, Paul E

1968-01-01

General theoretical methods and experimental techniques ; the uniform plasma slab-condenser system ; the hollow cylindrical plasma ; scattering of a plane electromagnetic wave by a plasma column in steady magnetic fields (cold plasma approximation) ; hot non-uniform plasma column ; metallic and dielectric resonance probes, plasma-dielectric coated antenna, general considerations.

Plasma-driven liners

International Nuclear Information System (INIS)

Kilic, H.; Linhart, J.G.; Bortolotti, A.; Nardi, V.

1992-01-01

The deposition of thermal energy by laser or ion beams in an ablator is capable of producing a very large acceleration of the adjacent pusher - for power densities of 100 Terrawatts/cm 2 , ablator pressure in the range of 10 Mbar is attainable. In the case of a plasma drive such driving pressures and accelerations are not directly possible. When a snowplough (SP) is used to accelerate a thin liner, the driving pressure is that of the magnetic piston pushing the SP, i.e. at most 0.1 Mbar. However, the initial radius r 0 of the liner can be a few centimeters, instead of 1 (mm) as in the case in direct pellet implosions. In order to compete with the performance of the beam-driven liners, the plasma drive must demonstrate that a) thin liner retains a high density during the implosion (lasting a fraction of a μsec); b) radial compression ratio r 0 /r min of the order of 100 can be attained. It is also attractive to consider the staging of two or more liners in order to get sharpening and amplifications of the pressure and/or radiation pulse. If a) and b) are verified then the final pressures produced will be comparable with those of the beam-driven implosions. (author) 5 refs., 3 figs

Resonance absorption of ICRF wave in edge plasma

International Nuclear Information System (INIS)

Sugihara, Ryo; Yamanaka, Kaoru.

1987-07-01

An edge plasma is shown to significantly absorb ICRF wave when a resonant triplet, a cutoff-resonance-cutoff triplet, is constructed in the evanescent region. Two-ion-component plasmas in a torus are considered though the plasmas are modeled by a slab in which the density changes linearly along the x-axis. The resonance is a perpendicular-ion-cyclotron resonance, i.e., an Alfven resonance, and is formed when the applied frequency ω is smaller than the local cyclotron frequency, at the edge of the antenna side, of the lighter species of ions. Roughly the absorption rate A b is given by M 2 for M 2 >> S 2 and S 4 for S 2 >> M 2 where M = k y l and S ≅ k z l and l is a scale length of the order of the plasma minor radius and k y and k z are the perpendicular and the parallel components of the wave vector. It is noted that the both quantities, M and S, readily become of the order of unity. Since A b is not very sensitive to the density ratio of the two ion species, a few percent of impurities may cause a significant absorption. As the mass ratio of the two ion species comes close to unity the triplet forms readily. Therefore a D-T plasma seems to suffer more easily this kind of resonance absorption than a D-H plasma. (author)

Resonant magnetohydrodynamic waves in high-beta plasmas

International Nuclear Information System (INIS)

Ruderman, M. S.

2009-01-01

When a global magnetohydrodynamic (MHD) wave propagates in a weakly dissipative inhomogeneous plasma, the resonant interaction of this wave with either local Alfven or slow MHD waves is possible. This interaction occurs at the resonant position where the phase velocity of the global wave coincides with the phase velocity of either Alfven or slow MHD waves. As a result of this interaction a dissipative layer embracing the resonant position is formed, its thickness being proportional to R -1/3 , where R>>1 is the Reynolds number. The wave motion in the resonant layer is characterized by large amplitudes and large gradients. The presence of large gradients causes strong dissipation of the global wave even in very weakly dissipative plasmas. Very often the global wave motion is characterized by the presence of both Alfven and slow resonances. In plasmas with small or moderate plasma beta β, the resonance positions corresponding to the Alfven and slow resonances are well separated, so that the wave motion in the Alfven and slow dissipative layers embracing the Alfven and slow resonant positions, respectively, can be studied separately. However, when β > or approx. R 1/3 , the two resonance positions are so close that the two dissipative layers overlap. In this case, instead of two dissipative layers, there is one mixed Alfven-slow dissipative layer. In this paper the wave motion in such a mixed dissipative layer is studied. It is shown that this motion is a linear superposition of two motions, one corresponding to the Alfven and the other to the slow dissipative layer. The jump of normal velocity across the mixed dissipative layer related to the energy dissipation rate is equal to the sum of two jumps, one that occurs across the Alfven dissipative layer and the other across the slow dissipative layer.

Quantum tunneling resonant electron transfer process in Lorentzian plasmas

International Nuclear Information System (INIS)

Hong, Woo-Pyo; Jung, Young-Dae

2014-01-01

The quantum tunneling resonant electron transfer process between a positive ion and a neutral atom collision is investigated in nonthermal generalized Lorentzian plasmas. The result shows that the nonthermal effect enhances the resonant electron transfer cross section in Lorentzian plasmas. It is found that the nonthermal effect on the classical resonant electron transfer cross section is more significant than that on the quantum tunneling resonant charge transfer cross section. It is shown that the nonthermal effect on the resonant electron transfer cross section decreases with an increase of the Debye length. In addition, the nonthermal effect on the quantum tunneling resonant electron transfer cross section decreases with increasing collision energy. The variation of nonthermal and plasma shielding effects on the quantum tunneling resonant electron transfer process is also discussed

Numerical Study on Blast Wave Propagation Driven by Unsteady Ionization Plasma

International Nuclear Information System (INIS)

Ogino, Yousuke; Sawada, Keisuke; Ohnishi, Naofumi

2008-01-01

Understanding the dynamics of laser-produced plasma is essential for increasing the available thrust and energy conversion efficiency from a pulsed laser to a blast wave in a gas-driven laser-propulsion system. The performance of a gas-driven laser-propulsion system depends heavily on the laser-driven blast wave dynamics as well as on the ionizing and/or recombining plasma state that sustains the blast wave. In this study, we therefore develop a numerical simulation code for a laser-driven blast wave coupled with time-dependent rate equations to explore the formation of unsteady ionizing plasma produced by laser irradiation. We will also examine the various properties of blast waves and unsteady ionizing plasma for different laser input energies

Model for resonant plasma probe.

Energy Technology Data Exchange (ETDEWEB)

Warne, Larry Kevin; Johnson, William Arthur; Hebner, Gregory Albert; Jorgenson, Roy E.; Coats, Rebecca Sue

2007-04-01

This report constructs simple circuit models for a hairpin shaped resonant plasma probe. Effects of the plasma sheath region surrounding the wires making up the probe are determined. Electromagnetic simulations of the probe are compared to the circuit model results. The perturbing effects of the disc cavity in which the probe operates are also found.

Electron cyclotron resonance plasma photos

Energy Technology Data Exchange (ETDEWEB)

Racz, R.; Palinkas, J. [Institute of Nuclear Research (ATOMKI), H-4026 Debrecen, Bem ter 18/c (Hungary); University of Debrecen, H-4010 Debrecen, Egyetem ter 1 (Hungary); Biri, S. [Institute of Nuclear Research (ATOMKI), H-4026 Debrecen, Bem ter 18/c (Hungary)

2010-02-15

In order to observe and study systematically the plasma of electron cyclotron resonance (ECR) ion sources (ECRIS) we made a high number of high-resolution visible light plasma photos and movies in the ATOMKI ECRIS Laboratory. This required building the ECR ion source into an open ECR plasma device, temporarily. An 8MP digital camera was used to record photos of plasmas made from Ne, Ar, and Kr gases and from their mixtures. We studied and recorded the effect of ion source setting parameters (gas pressure, gas composition, magnetic field, and microwave power) to the shape, color, and structure of the plasma. The analysis of the photo series gave us many qualitative and numerous valuable physical information on the nature of ECR plasmas.

Electron cyclotron resonance plasma photos

International Nuclear Information System (INIS)

Racz, R.; Palinkas, J.; Biri, S.

2010-01-01

In order to observe and study systematically the plasma of electron cyclotron resonance (ECR) ion sources (ECRIS) we made a high number of high-resolution visible light plasma photos and movies in the ATOMKI ECRIS Laboratory. This required building the ECR ion source into an open ECR plasma device, temporarily. An 8MP digital camera was used to record photos of plasmas made from Ne, Ar, and Kr gases and from their mixtures. We studied and recorded the effect of ion source setting parameters (gas pressure, gas composition, magnetic field, and microwave power) to the shape, color, and structure of the plasma. The analysis of the photo series gave us many qualitative and numerous valuable physical information on the nature of ECR plasmas.

Nonlinear mode conversion with chaotic soliton generation at plasma resonance

International Nuclear Information System (INIS)

Pietsch, H.; Laedke, E.W.; Spatschek, K.H.

1993-01-01

The resonant absorption of electromagnetic waves near the critical density in inhomogeneous plasmas is studied. A driven nonlinear Schroedinger equation for the mode-converted oscillations is derived by multiple-scaling techniques. The model is simulated numerically. The generic transition from a stationary to a time-dependent solution is investigated. Depending on the parameters, a time-chaotic behavior is found. By a nonlinear analysis, based on the inverse scattering transform, solitons of a corresponding integrable equation are identified as the dominant coherent structures of the chaotic dynamics. Finally, a map is presented which predicts chaotic soliton generation and emission at the critical density. Its qualitative behavior, concerning the bifurcation points, is in excellent agreement with the numerical simulations

Clara Schumann: 'A woman's love and life': a psychoanalytic interpretation.

Science.gov (United States)

Halberstadt-Freud, H C

1995-01-01

This study was undertaken to demonstrate how psychoanalysis can shed new light on a much studied life history. Clara's emotional life knew a sequence of losses and "prohibited" intimate relationships that created grave loyalty, identity, and identificatory conflicts for her. Since her early childhood, when her father forced her to give up her mother, she had been forced into a choice between the love objects most dear to her and the one on whom she depended for her emotional survival. This resulted in her later repetition compulsion to maneuver herself into the same conflict of loyalty and in her hesitation to decide when choosing one object meant losing the other. Clara had never known a normal separation, only loss and abandonment. She strove to combine the incompatible and succeeded in remaining loyal not only to her mother and father, but also to Robert Schumann, and eventually to Johannes Brahms. Clara Schumann's ideals were conflicted not only because she was educated by two men who were fighting each other, but also because her father, as well as Robert, had internally inconsistent and ambiguous ideas about women. Clara not only had to be obedient and creative, but self-sufficient at the same time. She was partially able to satisfy her own and her partner's needs and solve her deficiencies by projective identification, choosing taciturn men, more maternal than she.

Nonlinear relativistic plasma resonance: Renormalization group approach

Energy Technology Data Exchange (ETDEWEB)

Metelskii, I. I., E-mail: metelski@lebedev.ru [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Kovalev, V. F., E-mail: vfkvvfkv@gmail.com [Dukhov All-Russian Research Institute of Automatics (Russian Federation); Bychenkov, V. Yu., E-mail: bychenk@lebedev.ru [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

2017-02-15

An analytical solution to the nonlinear set of equations describing the electron dynamics and electric field structure in the vicinity of the critical density in a nonuniform plasma is constructed using the renormalization group approach with allowance for relativistic effects of electron motion. It is demonstrated that the obtained solution describes two regimes of plasma oscillations in the vicinity of the plasma resonance— stationary and nonstationary. For the stationary regime, the spatiotemporal and spectral characteristics of the resonantly enhanced electric field are investigated in detail and the effect of the relativistic nonlinearity on the spatial localization of the energy of the plasma relativistic field is considered. The applicability limits of the obtained solution, which are determined by the conditions of plasma wave breaking in the vicinity of the resonance, are established and analyzed in detail for typical laser and plasma parameters. The applicability limits of the earlier developed nonrelativistic theories are refined.

Resonant and hollow beam generation of plasma channels

International Nuclear Information System (INIS)

Alexeev, I.; Kim, K.Y.; Fan, J.; Parra, E.; Milchberg, H.M.; Margolin, L.Ya.; Pyatnitskii, L.N.

2001-01-01

We report two variations on plasma channel generation using the propagation of intense Bessel beams. In the first experiment, the propagation of a high intensity Bessel beam in neutral gas is observed to give rise to resonantly enhanced plasma channel generation, resulting from resonant self-trapping of the beam and enhanced laser-plasma heating. In the second experiment, a high power, hollow Bessel beam (J 5 ) is produced and the optical breakdown of a gas target and the generation of a tubular plasma channel with such a beam is realized for the first time. Hydrodynamic simulations of the laser-plasma interaction of are in good agreement with the results of both experiments

Resonant quasiparticles in plasma turbulence

International Nuclear Information System (INIS)

Mendonca, J.T.; Bingham, R.; Shukla, P.K.

2003-01-01

A general view is proposed on wave propagation in fluids and plasmas where the resonant interaction of monochromatic waves with quasiparticles is considered. A kinetic equation for quasiparticles is used to describe the broadband turbulence interacting with monochromatic waves. Resonant interactions occur when the phase velocity of the long wavelength monochromatic wave is nearly equal to the group velocity of short wavelength wave packets, or quasiparticles, associated with the turbulent spectrum. It is shown that quasiparticle Landau damping can take place, as well as quasiparticle beam instabilities, thus establishing a direct link between short and large wavelength perturbations of the medium. This link is distinct from the usual picture of direct and inverse energy cascades, and it can be used as a different paradigm for the fluid and plasma turbulence theories

Doubly excited P-wave resonance states of H− in Debye plasmas

International Nuclear Information System (INIS)

Jiao, L. G.; Ho, Y. K.

2013-01-01

We investigate the doubly excited P-wave resonance states of H − system in Debye plasmas modeled by static screened Coulomb potentials. The screening effects of the plasma environment on resonance parameters (energy and width) are investigated by employing the complex-scaling method with Hylleraas-type wave functions for both the shape and Feshbach resonances associated with the H(N = 2 to 6) thresholds. Under the screening conditions, the H(N) threshold states are no longer l degenerate, and all the H − resonance energy levels are shifted away from their unscreened values toward the continuum. The influence of Debye plasmas on resonance widths has also been investigated. The shape resonance widths are broadened with increasing plasma screening strength, whereas the Feshbach resonance widths would generally decrease. Our results associated with the H(N = 2) and H(N = 3) thresholds are compared with others in the literature

Ion heating at the cyclotron resonance in plasmas magnetically confined in a toroidal octupole field

International Nuclear Information System (INIS)

Barter, J.D.

1976-01-01

Ion temperatures as high as 600 eV have been produced using rf wave heating at the ion cyclotron resonance frequency in a toroidal octupole magnetic field. Rf is coupled to the plasma with an externally driven ''fifth'' hoop which forms the inductive leg of an oscillator tank circuit. Power levels up to 1 MW at 1 to 3 MHz have been applied for periods up to 2 msec. Plasmas produced either by ECRH or by gun injection are simulated with a computer program in which known particle and energy production and loss mechanisms are used to predict the spatially averaged time behaviour of the plasma in the presence of the applied ion heating. The program can be used to calculate the consequences of the heating model in the presence of many cooling mechanisms which may each have a separate dependence on instantaneous plasma parameters. Experimental quantities compared to computer predictions include density, ion temperature, and loading of the hoop by the plasma, both resistive and reactive, and neutral reflux from the wall by electron and ion impact. Wave penetration to the resonance zone is good up to the highest densities available (6 x 10 12 cm -3 by gun injection) in good agreement with theory. Neutral reflux from the walls and the large charge exchange cooling which results is the dominant loss mechanism at the higher hoop voltages

Maurice Schumann, la voix de la résistance

OpenAIRE

Tellier, Thibault

2012-01-01

Maurice Schumann a participé au premier plan à la Résistance contre l’ennemi allemand. Il a été, au cours des cinq années de guerre, la voix de la résistance de la France libre qui, chaque jour, s’adressait aux Français et aux combattants de l’ombre pour les encourager à poursuivre leur périlleux et courageux engagement. Ce texte a donc pour but de présenter les grandes lignes de son engagement et montrer en quoi sa fonction de porte-parole de la France Libre le situe parfaitement dans les pe...

Radiation reaction effect on laser driven auto-resonant particle acceleration

International Nuclear Information System (INIS)

Sagar, Vikram; Sengupta, Sudip; Kaw, P. K.

2015-01-01

The effects of radiation reaction force on laser driven auto-resonant particle acceleration scheme are studied using Landau-Lifshitz equation of motion. These studies are carried out for both linear and circularly polarized laser fields in the presence of static axial magnetic field. From the parametric study, a radiation reaction dominated region has been identified in which the particle dynamics is greatly effected by this force. In the radiation reaction dominated region, the two significant effects on particle dynamics are seen, viz., (1) saturation in energy gain by the initially resonant particle and (2) net energy gain by an initially non-resonant particle which is caused due to resonance broadening. It has been further shown that with the relaxation of resonance condition and with optimum choice of parameters, this scheme may become competitive with the other present-day laser driven particle acceleration schemes. The quantum corrections to the Landau-Lifshitz equation of motion have also been taken into account. The difference in the energy gain estimates of the particle by the quantum corrected and classical Landau-Lifshitz equation is found to be insignificant for the present day as well as upcoming laser facilities

Resonances and surface waves in bounded plasmas

International Nuclear Information System (INIS)

Bowers, K.J.; Qui, D.W.; Smith, H.B.; Birdsall, C.K.

1999-01-01

Surface waves provide a promising means of creating large, area plasmas. These waves can uniformly distribute the excitation energy and while presenting a small resistance and zero reactance to the driving source. Experimentally and in the simulations, the electron temperature is low (like 1--3 eV) as is the plasma potential (like 10 Te). The use of surface waves experimentally, and now industrially, to sustain large area plasma sources with device size is comparable to free space wavelength have motivated the authors to refine the theories of [1] and [2] to be fully electromagnetic. The wave dispersion predicted by the electromagnetic theory differs from the predictions of the prior theories and the results illuminate limitations of the electrostatic model. The use of surface waves have also motivated them to explore the mechanisms by which surface waves heat the plasma. In the 1d electrostatic simulations high velocity electron bunches are formed in the sheaths and are alternatively accelerated from each sheath into the bulk plasma each RF cycle. They speculate similar mechanisms provide the ionization in surface wave discharges. They also see in these simulations the plasma makes an abrupt transition from capacitively coupled to resistively coupled and the series resonance locks onto the drive frequency; these abrupt transitions resemble mode-jumping seen experimentally in large area sources. Furthermore, the density profile of the plasma tracks the drive frequency while in the resonant mode giving a new mechanism by which the plasma parameters can be controlled. They are currently investigating the effect of the driving electrode shape has on these resonances and conducting 2d simulations of a large area surface wave source to explore the ignition of surface wave devices and how the plasma fills in the device

Degenerate four-wave mixing mediated by ponderomotive-force-driven plasma gratings

International Nuclear Information System (INIS)

Lee, K.-H.; Lin, M.-W.; Pai, C.-H.; Ha, L.-C.; Lin, J.-Y.; Wang, J.; Chen, S.-Y.

2007-01-01

Degenerate four-wave mixing mediated by ponderomotive-force-driven plasma gratings is demonstrated in the near-infrared regime. The quadratic dependence of the reflectivity of the probe pulse on plasma density indicates that the mixing is caused by the quasineutral plasma grating driven by the laser ponderomotive force. The experiment verifies that ponderomotive force is an effective means to produce a large-amplitude short-period plasma grating, which has many important applications in ultrahigh-intensity optics. In particular, such a grating is a crucial element for the development of plasma phase-conjugate mirrors that can be used to restore the wave-front distortion that is ubiquitous in nonlinear propagation

On Day-to-Day Variability of Global Lightning Activity as Quantified from Background Schumann Resonance Observations

Science.gov (United States)

Mushtak, V. C.; Williams, E. R.

2011-12-01

Among the palette of methods (satellite, VLF, ELF) for monitoring global lightning activity, observations of the background Schumann resonances (SR) provide a unique prospect for estimating the integrated activity of global lightning activity in absolute units (coul2 km2/sec). This prospect is ensured by the SR waves' low attenuation, with wavelengths commensurate with the dimensions of dominant regional lightning "chimneys", and by the accumulating methodology for background SR techniques. Another benefit is the reduction of SR measurements into a compact set of resonance characteristics (modal frequencies, intensities, and quality factors). Suggested and tested in numerical simulations by T.R. Madden in the 1960s, the idea to invert the SR characteristics for the global lightning source has been farther developed, statistically substantiated, and practically realized here on the basis of the computing power and the quantity of experimental material way beyond what the SR pioneers had at their disposal. The critical issue of the quality of the input SR parameters is addressed by implementing a statistically substantiated sanitizing procedure to dispose of the fragments of the observed time series containing unrepresentative elements - local interference of various origin and strong ELF transients originating outside the major "chimneys" represented in the source model. As a result of preliminary research, a universal empirical sanitizing criterion has been established. Due to the fact that the actual observations have been collected from a set of individually organized ELF stations with various equipment sets and calibration techniques, the relative parameters in both input (the intensities) and output (the "chimney" activities) are being used as far as possible in the inversion process to avoid instabilities caused by calibration inconsistencies. The absolute regional activities - and so the sought for global activity in absolute units - is determined in the

Spectrum of resonant plasma oscillations in long Josephson junctions

International Nuclear Information System (INIS)

Holst, T.

1996-01-01

An analysis is presented for the amplitude of the plasma oscillations in the zero-voltage state of a long and narrow Josephson tunnel junction. The calculation is valid for arbitrary normalized junction length and arbitrary bias current. The spectrum of the plasma resonance is found numerically as solutions to an analytical equation. The low-frequency part of the spectrum contains a single resonance, which is known to exist also in the limit of a short and narrow junction. Above a certain cutoff frequency, a series of high-frequency standing wave plasma resonances is excited, a special feature of long Josephson junctions. copyright 1996 The American Physical Society

Atomic resonances in nuclear fusion plasmas

International Nuclear Information System (INIS)

Clauser, C. F.; Barrachina, R. O.

2013-01-01

We present a study of zero energy resonances of photoionization and radiative recombination cross section for the different species in a fusion reactor. In this context, the interaction potential is screened and its typical length depends on the plasma density and temperature. Due to the nature of these resonances, we propose other atomic processes in which they can take place. Finally, we show the density and temperature conditions where these resonances occur and their probable consequence on the reactor performance. (author)

AWAKE, The Advanced Proton Driven Plasma Wakefield Acceleration Experiment at CERN

CERN Document Server

Gschwendtner, E.; Amorim, L.; Apsimon, R.; Assmann, R.; Bachmann, A.M.; Batsch, F.; Bauche, J.; Berglyd Olsen, V.K.; Bernardini, M.; Bingham, R.; Biskup, B.; Bohl, T.; Bracco, C.; Burrows, P.N.; Burt, G.; Buttenschon, B.; Butterworth, A.; Caldwell, A.; Cascella, M.; Chevallay, E.; Cipiccia, S.; Damerau, H.; Deacon, L.; Dirksen, P.; Doebert, S.; Dorda, U.; Farmer, J.; Fedosseev, V.; Feldbaumer, E.; Fiorito, R.; Fonseca, R.; Friebel, F.; Gorn, A.A.; Grulke, O.; Hansen, J.; Hessler, C.; Hofle, W.; Holloway, J.; Huther, M.; Jaroszynski, D.; Jensen, L.; Jolly, S.; Joulaei, A.; Kasim, M.; Keeble, F.; Li, Y.; Liu, S.; Lopes, N.; Lotov, K.V.; Mandry, S.; Martorelli, R.; Martyanov, M.; Mazzoni, S.; Mete, O.; Minakov, V.A.; Mitchell, J.; Moody, J.; Muggli, P.; Najmudin, Z.; Norreys, P.; Oz, E.; Pardons, A.; Pepitone, K.; Petrenko, A.; Plyushchev, G.; Pukhov, A.; Rieger, K.; Ruhl, H.; Salveter, F.; Savard, N.; Schmidt, J.; Seryi, A.; Shaposhnikova, E.; Sheng, Z.M.; Sherwood, P.; Silva, L.; Soby, L.; Sosedkin, A.P.; Spitsyn, R.I.; Trines, R.; Tuev, P.V.; Turner, M.; Verzilov, V.; Vieira, J.; Vincke, H.; Wei, Y.; Welsch, C.P.; Wing, M.; Xia, G.; Zhang, H.

2016-01-01

The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) aims at studying plasma wakefield generation and electron acceleration driven by proton bunches. It is a proof-of-principle R&D experiment at CERN and the world's first proton driven plasma wakefield acceleration experiment. The AWAKE experiment will be installed in the former CNGS facility and uses the 400 GeV/c proton beam bunches from the SPS. The first experiments will focus on the self-modulation instability of the long (rms ~12 cm) proton bunch in the plasma. These experiments are planned for the end of 2016. Later, in 2017/2018, low energy (~15 MeV) electrons will be externally injected to sample the wakefields and be accelerated beyond 1 GeV. The main goals of the experiment will be summarized. A summary of the AWAKE design and construction status will be presented.

Runaway tails in magnetized plasmas

Science.gov (United States)

Moghaddam-Taaheri, E.; Vlahos, L.; Rowland, H. L.; Papadopoulos, K.

1985-01-01

The evolution of a runaway tail driven by a dc electric field in a magnetized plasma is analyzed. Depending on the strength of the electric field and the ratio of plasma to gyrofrequency, there are three different regimes in the evolution of the tail. The tail can be (1) stable with electrons accelerated to large parallel velocities, (2) unstable to Cerenkov resonance because of the depletion of the bulk and the formation of a positive slope, (3) unstable to the anomalous Doppler resonance instability driven by the large velocity anisotropy in the tail. Once an instability is triggered (Cerenkov or anomalous Doppler resonance) the tail relaxes into an isotropic distribution. The role of a convection type loss term is also discussed.

Nonlinear structure formation in ion-temperature-gradient driven drift waves in pair-ion plasma with nonthermal electron distribution

Science.gov (United States)

Razzaq, Javaria; Haque, Q.; Khan, Majid; Bhatti, Adnan Mehmood; Kamran, M.; Mirza, Arshad M.

2018-02-01

Nonlinear structure formation in ion-temperature-gradient (ITG) driven waves is investigated in pair-ion plasma comprising ions and nonthermal electrons (kappa, Cairns). By using the transport equations of the Braginskii model, a new set of nonlinear equations are derived. A linear dispersion relation is obtained and discussed analytically as well as numerically. It is shown that the nonthermal population of electrons affects both the linear and nonlinear characteristics of the ITG mode in pair-ion plasma. This work will be useful in tokamaks and stellarators where non-Maxwellian population of electrons may exist due to resonant frequency heating, electron cyclotron heating, runaway electrons, etc.

BRIEF COMMUNICATION: On the drift kinetic equation driven by plasma flows

Science.gov (United States)

Shaing, K. C.

2010-07-01

A drift kinetic equation that is driven by plasma flows has previously been derived by Shaing and Spong 1990 (Phys. Fluids B 2 1190). The terms that are driven by particle speed that is parallel to the magnetic field B have been neglected. Here, such terms are discussed to examine their importance to the equation and to show that these terms do not contribute to the calculations of plasma viscosity in large aspect ratio toroidal plasmas, e.g. tokamaks and stellarators.

The Current-Driven, Ion-Acoustic Instability in a Collisionless Plasma

DEFF Research Database (Denmark)

Michelsen, Poul; Pécseli, Hans; Juul Rasmussen, Jens

1979-01-01

The current-driven, ion-acoustic instability was investigated by means of an experiment performed in a collisionless plasma produced in a single-ended Q-machine. Reflections at the ends of the plasma column gave rise to a standing wave. Parameters of the instability were investigated, and it was ......, and it was demonstrated that the fluctuations in the plasma column behave as a classical Van der Pol oscillator. Accurate measurements of the growth rate of the instability can be performed by making explicit use of the particular properties of such a system.......The current-driven, ion-acoustic instability was investigated by means of an experiment performed in a collisionless plasma produced in a single-ended Q-machine. Reflections at the ends of the plasma column gave rise to a standing wave. Parameters of the instability were investigated...

Interaction of plasma vortices with resonant particles

DEFF Research Database (Denmark)

Jovanovic, D.; Pécseli, Hans; Juul Rasmussen, J.

1990-01-01

Kinetic effects associated with the electron motion along magnetic field lines in low‐beta plasmas are studied. Using the gyrokinetic description of electrons, a kinetic analog of the reduced magnetohydrodynamic equations is derived, and it is shown that in the strongly nonlinear regime...... particles. The evolution equations indicate the possibility of excitation of plasma vortices by electron beams....... they possess localized solutions in the form of dipolar vortices, which can efficiently interact with resonant electrons. In the adiabatic limit, evolution equations are derived for the vortex parameters, describing exchange of the energy, enstrophy, and of the Poynting vector between the vortex and resonant...

γ -Ray Generation from Plasma Wakefield Resonant Wiggler

Science.gov (United States)

Lei, Bifeng; Wang, Jingwei; Kharin, Vasily; Zepf, Matt; Rykovanov, Sergey

2018-03-01

A flexible gamma-ray radiation source based on the resonant laser-plasma wakefield wiggler is proposed. The wiggler is achieved by inducing centroid oscillations of a short laser pulse in a plasma channel. Electrons (self-)injected in such a wakefield experience both oscillations due to the transverse electric fields and energy gain due to the longitudinal electric field. The oscillations are significantly enhanced when the laser pulse centroid oscillations are in resonance with the electron betatron oscillations, extending the radiation spectrum to the gamma-ray range. The polarization of the radiation can be easily controlled by adjusting the injection of the laser pulse into the plasma channel.

Nonlinear response and bistability of driven ion acoustic waves

Science.gov (United States)

Akbari-Moghanjoughi, M.

2017-08-01

The hydrodynamic model is used to obtain a generalized pseudoforce equation through which the nonlinear response of periodically driven ion acoustic waves is studied in an electron-ion plasma with isothermal and adiabatic ion fluids. The pseudotime series, corresponding to different driving frequencies, indicates that nonlinearity effects appear more strongly for smaller frequency values. The existence of extra harmonic resonances in the nonlinear amplitude spectrum is a clear indication of the interaction of an external force with harmonic components of the nonlinear ion acoustic waves. It is shown that many plasma parameters significantly and differently affect the nonlinear resonance spectrum of ion acoustic excitations. A heuristic but accurate model for the foldover effect is used which quite satisfactorily predicts the bistability of driven plasma oscillations. It is remarked that the characteristic resonance peak of isothermal ion plasma oscillations appears at lower frequencies but is stronger compared to that of adiabatic ions. Comparison of the exact numerical results for fully nonlinear and approximate (weakly nonlinear) models indicates that a weakly nonlinear model exaggerates the hysteresis and jump phenomenon for higher values of the external force amplitude.

Weibel instability mediated collisionless shocks using intense laser-driven plasmas

Science.gov (United States)

Palaniyappan, Sasikumar; Fiuza, Federico; Huang, Chengkun; Gautier, Donald; Ma, Wenjun; Schreiber, Jorg; Raymer, Abel; Fernandez, Juan; Shimada, Tom; Johnson, Randall

2017-10-01

The origin of cosmic rays remains a long-standing challenge in astrophysics and continues to fascinate physicists. It is believed that ``collisionless shocks'' - where the particle Coulomb mean free path is much larger that the shock transition - are a dominant source of energetic cosmic rays. These shocks are ubiquitous in astrophysical environments such as gamma-ray bursts, supernova remnants, pulsar wind nebula and coronal mass ejections from the sun. A particular type of electromagnetic plasma instability known as Weibel instability is believed to be the dominant mechanism behind the formation of these collisionless shocks in the cosmos. The understanding of the microphysics behind collisionless shocks and their particle acceleration is tightly related with nonlinear basic plasma processes and remains a grand challenge. In this poster, we will present results from recent experiments at the LANL Trident laser facility studying collisionless shocks using intense ps laser (80J, 650 fs - peak intensity of 1020 W/cm2) driven near-critical plasmas using carbon nanotube foam targets. A second short pulse laser driven protons from few microns thick gold foil is used to radiograph the main laser-driven plasma. Work supported by the LDRD program at LANL.

Upper Hybrid Resonance of Microwaves with a Large Magnetized Plasma Sheet

International Nuclear Information System (INIS)

Huo Wenqing; Guo Shijie; Ding Liang; Xu Yuemin

2013-01-01

A large magnetized plasma sheet with size of 60 cm × 60 cm × 2 cm was generated by a linear hollow cathode discharge under the confinement of a uniform magnetic field generated by a Helmholtz Coil. The microwave transmission characteristic of the plasma sheet was measured for different incident frequencies, in cases with the electric field polarization of the incident microwave either perpendicular or parallel to the magnetic field. In this measurement, parameters of the plasma sheet were changed by varying the discharge current and magnetic field intensity. In the experiment, upper hybrid resonance phenomena were observed when the electric field polarization of the incident wave was perpendicular to the magnetic field. These resonance phenomena cannot be found in the case of parallel polarization incidence. This result is consistent with theoretical consideration. According to the resonance condition, the electron density values at the resonance points are calculated under various experimental conditions. This kind of resonance phenomena can be used to develop a specific method to diagnose the electron density of this magnetized plasma sheet apparatus. Moreover, it is pointed out that the operating parameters of the large plasma sheet in practical applications should be selected to keep away from the upper hybrid resonance point to prevent signals from polarization distortion

Electron cyclotron resonance heating assisted plasma startup in the Tore Supra tokamak

International Nuclear Information System (INIS)

Bucalossi, J.; Hertout, P.; Lennholm, M.; Saint-Laurent, F.; Bouquey, F.; Darbos, C.; Traisnel, E.

2009-04-01

ECRH assisted plasma startup at fundamental resonance is investigated in Tore Supra in view of ITER operation. ECRH pre-ionisation is found to be very efficient allowing plasma initiation in a wide range of pre-fill pressure compared to ohmic startup. Reliable assisted startup has been achieved at the ITER reference toroidal electric field (0.3 V/m) with 160 kW of ECRH. Resonance location scan indicates that the plasma is initiated at the resonance location and that the plasma current channel position had to be real-time controlled since the very beginning of the discharge to obtain robust plasma startup. (authors)

Resonant transducers for solid-state plasma density modulation

Energy Technology Data Exchange (ETDEWEB)

Hallock, Gary A., E-mail: hallock@ece.utexas.edu [The University of Texas at Austin, Austin, Texas 78701 (United States); Meier, Mark A., E-mail: mark.a.meier@exxonmobil.com [ExxonMobil Upstream Research Company, Houston, Texas 77389 (United States)

2016-04-15

We have developed transducers capable of modulating the plasma density and plasma density gradients in indium antimonide. These transducers make use of piezoelectric drivers to excite acoustic pressure resonance at 3λ/2, generating large amplitude standing waves and plasma density modulations. The plasma density has been directly measured using a laser diagnostic. A layered media model shows good agreement with the experimental measurements.

Wakefield excitation in plasma resonator by a sequence of relativistic electron bunches

International Nuclear Information System (INIS)

Kiselev, V.A.; Linnik, A.F.; Mirny, V.I.; Onishchenko, I.N.; Uskov, V.V.

2008-01-01

Wakefield excitation in a plasma resonator by a sequence of relativistic electron bunches with the purpose to increase excited field amplitude in comparison to waveguide case is experimentally investigated. A sequence of short electron bunches is produced by the linear resonant accelerator. Plasma resonator is formed at the beam-plasma discharge in rectangular metal waveguide filled with gas and closed by metal foil at entrance and movable short-circuited plunger at exit. Measurements of wakefield amplitude are performed showing considerably higher wakefield amplitude for resonator case

Electromagnetically Driven Plasma-Field Dynamics in Modified Ionosphere

Science.gov (United States)

Kochetov, Andrey; Terina, Galina

Under sounding of an artificial ionospheric turbulence by short probing radio pulses of ordinary polarization the two types of scattered signals were observed: a "caviton" signal (CS) and a "plasma" signal (PS), which appeared with the heating transmitter switching on and disap-peared after its switching off (G.I. Terina J. Atm. Terr. Phys, 57, 1995, 273, Izv. VUZov, Radiofizika, 39, 1998, 203). The scattered signal of PS type was revealed also after the heating switching off. It was called an "aftereffect plasma signal" (AEPS) (G.I. Terina Izv .VUZov, Radiofizika, 43, 2000, 958). This signal had large time and spatial delays and appeared mostly when corresponding PS had envelope fluctuations. The aftereffect phenomenon was expressed at time on CS by amplitude increasing at once after the heating transmitter turning off. The theoretical model of this phenomenon is proposed in and some peculiarities of the aftereffect phenomena of the scattered signals in modified ionospheric plasma are considered and discussed. For theoretical interpretation of the characteristics of CS and AEPS the numerical solution of nonlinear Shrüdinger equation (NSE) with driven extension were carried out in inhomogeneous plasma layer with linear electron density profile (A.V. Kochetov, V.A. Mironov, G.I. Terina, Adv. Space Reseacrh, 29, 2002, 1369) and for the one with prescribed density depletion (and A.V. Kochetov, G.I. Terina, Adv. Space Reseacrh, 38, 2006, 2490). The simulation results obtained for linear inhomogeneous plasma layer and for plasma one with density depletion al-low us to interpret the aftereffect of CS and PS qualitatively. The field amplitude increase at relaxation stage displayed at calculations allows us to interpret of CS aftereffect. The large time delays of AEPS can be explained as a result of powerful radio waves trapping in the forming at the plasma resonance regions density depletions (E. Mjøhus, J. Geophys. Res. 103, 1998, 14711; B. Eliasson and L. Stenflo, J

Measurements of time average series resonance effect in capacitively coupled radio frequency discharge plasma

International Nuclear Information System (INIS)

Bora, B.; Bhuyan, H.; Favre, M.; Wyndham, E.; Chuaqui, H.; Kakati, M.

2011-01-01

Self-excited plasma series resonance is observed in low pressure capacitvely coupled radio frequency discharges as high-frequency oscillations superimposed on the normal radio frequency current. This high-frequency contribution to the radio frequency current is generated by a series resonance between the capacitive sheath and the inductive and resistive bulk plasma. In this report, we present an experimental method to measure the plasma series resonance in a capacitively coupled radio frequency argon plasma by modifying the homogeneous discharge model. The homogeneous discharge model is modified by introducing a correction factor to the plasma resistance. Plasma parameters are also calculated by considering the plasma series resonances effect. Experimental measurements show that the self-excitation of the plasma series resonance, which arises in capacitive discharge due to the nonlinear interaction of plasma bulk and sheath, significantly enhances both the Ohmic and stochastic heating. The experimentally measured total dissipation, which is the sum of the Ohmic and stochastic heating, is found to increase significantly with decreasing pressure.

Numerical simulation of plasma processes driven by transverse ion heating

Science.gov (United States)

Singh, Nagendra; Chan, C. B.

1993-01-01

The plasma processes driven by transverse ion heating in a diverging flux tube are investigated with numerical simulation. The heating is found to drive a host of plasma processes, in addition to the well-known phenomenon of ion conics. The downward electric field near the reverse shock generates a doublestreaming situation consisting of two upflowing ion populations with different average flow velocities. The electric field in the reverse shock region is modulated by the ion-ion instability driven by the multistreaming ions. The oscillating fields in this region have the possibility of heating electrons. These results from the simulations are compared with results from a previous study based on a hydrodynamical model. Effects of spatial resolutions provided by simulations on the evolution of the plasma are discussed.

Lack of dependence on resonant error field of locked mode island size in ohmic plasmas in DIII-D

Science.gov (United States)

La Haye, R. J.; Paz-Soldan, C.; Strait, E. J.

2015-02-01

DIII-D experiments show that fully penetrated resonant n = 1 error field locked modes in ohmic plasmas with safety factor q95 ≳ 3 grow to similar large disruptive size, independent of resonant error field correction. Relatively small resonant (m/n = 2/1) static error fields are shielded in ohmic plasmas by the natural rotation at the electron diamagnetic drift frequency. However, the drag from error fields can lower rotation such that a bifurcation results, from nearly complete shielding to full penetration, i.e., to a driven locked mode island that can induce disruption. Error field correction (EFC) is performed on DIII-D (in ITER relevant shape and safety factor q95 ≳ 3) with either the n = 1 C-coil (no handedness) or the n = 1 I-coil (with ‘dominantly’ resonant field pitch). Despite EFC, which allows significantly lower plasma density (a ‘figure of merit’) before penetration occurs, the resulting saturated islands have similar large size; they differ only in the phase of the locked mode after typically being pulled (by up to 30° toroidally) in the electron diamagnetic drift direction as they grow to saturation. Island amplification and phase shift are explained by a second change-of-state in which the classical tearing index changes from stable to marginal by the presence of the island, which changes the current density profile. The eventual island size is thus governed by the inherent stability and saturation mechanism rather than the driving error field.

Plasma resonance in anisotropic layered high-Tc superconductors

DEFF Research Database (Denmark)

Sakai, Shigeki; Pedersen, Niels Falsig

1999-01-01

The plasma resonance is described theoretically by the inductive coupling model for a large stacked Josephson-junction system such as the intrinsic Josephson-junction array in anisotropic high- T-c superconductors. Eigenmodes of the plasma oscillation are analytically described and a numerical...

Non linear excitation of waves at the vicinity of plasma resonance

International Nuclear Information System (INIS)

Chiron, Arnaud

1992-01-01

This research thesis reports the study of the non linear evolution of ionic acoustic and plasma waves excited by resonant absorption of an electromagnetic wave, in a non collisional plasma, without external magnetic field, and with a parabolic density profile. The plasma resonance occurs about the density profile peak. The numerical resolution of the Zakharov equation system is performed to describe the coupled evolution of the plasma wave electric field envelope, and low frequency density disturbances. Experiments performed in the microwave domain show the existence of a new effect related to the modification of the electromagnetic wave propagation under the influence of plasma density disturbances created by the ponderomotive force. This effect which results in a collisional relaxation of plasma waves trapped in the cavity formed at resonance, cannot be taken into account by a numerical simulation using a capacitive pump field. Measurements showed that plasma waves were trapped and relaxing in a cavity with characteristic dimensions of some thousands of Debye lengths, and that the plasma wave in the cavity was stationary. A new turbulence regime is thus highlighted [fr

Current-driven parametric resonance in magnetic multilayers

International Nuclear Information System (INIS)

Wang, C; Seinige, H; Tsoi, M

2013-01-01

Current-induced parametric excitations were observed in point-contact spin-valve nanodevices. Point contacts were used to inject high densities of direct and microwave currents into spin valves, thus producing oscillating spin-transfer and Oersted-field torques on magnetic moments. The resulting magnetodynamics were observed electrically by measuring rectified voltage signals across the contact. In addition to the spin-torque-driven ferromagnetic resonance we observe doubled-frequency signals which correspond to the parametric excitation of magnetic moments. Numerical simulations suggest that while both spin-transfer torque and ac Oersted field contribute to the parametrically excited dynamics, the ac spin torque dominates, and dc spin torque can switch it on and off. The dc bias dependence of the parametric resonance signal enabled the mapping of instability regions characterizing the nonlinearity of the oscillation. (paper)

On square-wave-driven stochastic resonance for energy harvesting in a bistable system

Energy Technology Data Exchange (ETDEWEB)

Su, Dongxu, E-mail: sudx@iis.u-tokyo.ac.jp [Graduate School of Engineering, The University of Tokyo, Tokyo 1538505 (Japan); Zheng, Rencheng; Nakano, Kimihiko [Institute of Industrial Science, The University of Tokyo, Tokyo 1538505 (Japan); Cartmell, Matthew P [Department of Mechanical Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom)

2014-11-15

Stochastic resonance is a physical phenomenon through which the throughput of energy within an oscillator excited by a stochastic source can be boosted by adding a small modulating excitation. This study investigates the feasibility of implementing square-wave-driven stochastic resonance to enhance energy harvesting. The motivating hypothesis was that such stochastic resonance can be efficiently realized in a bistable mechanism. However, the condition for the occurrence of stochastic resonance is conventionally defined by the Kramers rate. This definition is inadequate because of the necessity and difficulty in estimating white noise density. A bistable mechanism has been designed using an explicit analytical model which implies a new approach for achieving stochastic resonance in the paper. Experimental tests confirm that the addition of a small-scale force to the bistable system excited by a random signal apparently leads to a corresponding amplification of the response that we now term square-wave-driven stochastic resonance. The study therefore indicates that this approach may be a promising way to improve the performance of an energy harvester under certain forms of random excitation.

On square-wave-driven stochastic resonance for energy harvesting in a bistable system

International Nuclear Information System (INIS)

Su, Dongxu; Zheng, Rencheng; Nakano, Kimihiko; Cartmell, Matthew P

2014-01-01

Stochastic resonance is a physical phenomenon through which the throughput of energy within an oscillator excited by a stochastic source can be boosted by adding a small modulating excitation. This study investigates the feasibility of implementing square-wave-driven stochastic resonance to enhance energy harvesting. The motivating hypothesis was that such stochastic resonance can be efficiently realized in a bistable mechanism. However, the condition for the occurrence of stochastic resonance is conventionally defined by the Kramers rate. This definition is inadequate because of the necessity and difficulty in estimating white noise density. A bistable mechanism has been designed using an explicit analytical model which implies a new approach for achieving stochastic resonance in the paper. Experimental tests confirm that the addition of a small-scale force to the bistable system excited by a random signal apparently leads to a corresponding amplification of the response that we now term square-wave-driven stochastic resonance. The study therefore indicates that this approach may be a promising way to improve the performance of an energy harvester under certain forms of random excitation

Nonequilibrium steady states and resonant tunneling in time-periodically driven systems with interactions

Science.gov (United States)

Qin, Tao; Hofstetter, Walter

2018-03-01

Time-periodically driven systems are a versatile toolbox for realizing interesting effective Hamiltonians. Heating, caused by excitations to high-energy states, is a challenge for experiments. While most setups so far address the relatively weakly interacting regime, it is of general interest to study heating in strongly correlated systems. Using Floquet dynamical mean-field theory, we study nonequilibrium steady states (NESS) in the Falicov-Kimball model, with time-periodically driven kinetic energy or interaction. We systematically investigate the nonequilibrium properties of the NESS. For a driven kinetic energy, we show that resonant tunneling, where the interaction is an integer multiple of the driving frequency, plays an important role in the heating. In the strongly correlated regime, we show that this can be well understood using Fermi's golden rule and the Schrieffer-Wolff transformation for a time-periodically driven system. We furthermore demonstrate that resonant tunneling can be used to control the population of Floquet states to achieve "photodoping." For driven interactions introduced by an oscillating magnetic field near a widely adopted Feshbach resonance, we find that the double occupancy is strongly modulated. Our calculations apply to shaken ultracold-atom systems and to solid-state systems in a spatially uniform but time-dependent electric field. They are also closely related to lattice modulation spectroscopy. Our calculations are helpful to understand the latest experiments on strongly correlated Floquet systems.

Plasma rotation under a driven radial current in a tokamak

International Nuclear Information System (INIS)

Chang, C.S.

1999-01-01

The neoclassical behaviour of plasma rotation under a driven radial electrical current is studied in a tokamak geometry. An ambipolar radial electric field develops instantly in such a way that the driven current is balanced by a return current j p in the plasma. The j p x B torque pushes the plasma into a new rotation state both toroidally and poloidally. An anomalous toroidal viscosity is needed to avoid an extreme toroidal rotation speed. It is shown that the poloidal rotation relaxes to a new equilibrium speed, which is in general smaller than the E x B poloidal speed, and that the timescale for the relaxation of poloidal rotation is the same as that of toroidal rotation generation, which is usually much longer than the ion-ion collision time. (author)

RF Electron Gun with Driven Plasma Cathode

CERN Document Server

Khodak, Igor

2005-01-01

It's known that RF guns with plasma cathodes based on solid-state dielectrics are able to generate an intense electron beam. In this paper we describe results of experimental investigation of the single cavity S-band RF gun with driven plasma cathode. The experimental sample of the cathode based on ferroelectric ceramics has been designed. Special design of the cathode permits to separate spatially processes of plasma development and electron acceleration. It has been obtained at RF gun output electron beam with particle energy ~500 keV, pulse current of 4 A and pulse duration of 80 ns. Results of experimental study of beam parameters are referred in. The gun is purposed to be applied as the intense electron beam source for electron linacs.

Edge localized mode control by resonant magnetic perturbations in tokamak plasmas

International Nuclear Information System (INIS)

Orain, Francois

2014-01-01

The growth of plasma instabilities called Edge Localized Modes (ELMs) in tokamaks results in the quasi-periodic relaxation of the edge pressure profile. These relaxations induce large heat fluxes which might be harmful for the divertor in ITER, thus ELM control is mandatory in ITER. One of the promising control methods planned in ITER is the application of external resonant magnetic perturbations (RMPs), already efficient for ELM mitigation/suppression in current tokamak experiments. However a better understanding of the interaction between ELMs, RMPs and plasma flows is needed to explain the experimental results and make reliable predictions for ITER. In this perspective, non-linear modeling of ELMs and RMPs is done with the reduced MHD code JOREK, in toroidal geometry including the X-point and the Scrape-Off Layer. The initial model has been further developed to describe self-consistent plasma flows - with the addition of the bi-fluid diamagnetic drifts, the neoclassical friction and a source of parallel rotation - and to simulate the RMP penetration consistently with the plasma response. As a first step, the plasma response to RMPs (without ELMs) is studied for JET, MAST and ITER realistic plasma parameters and geometry. The general behaviour of the plasma/RMP interaction is similar for the three studied cases: RMPs are generally screened by the formation of response currents, induced by the plasma rotation on the resonant surfaces. RMPs however penetrate at the very edge where an ergodic zone is formed. The amplification of the non-resonant spectrum of the magnetic perturbations is also observed in the core. The edge ergodization induces an enhanced transport at the edge, which slightly degrades the pedestal profiles. RMPs also generate the 3D-deformation of the plasma boundary with a maximum deformation near the X-point where lobe structures are formed. Then the full dynamics of a multi-ELM cycle (without RMPs) is modeled for the first time in realistic

Enhanced resonant second harmonic generation in plasma based on density transition

Directory of Open Access Journals (Sweden)

Kant Niti

2015-06-01

Full Text Available Resonant second harmonic generation of a relativistic self-focusing laser in plasma with density ramp profile has been investigated. A high intense Gaussian laser beam generates resonant second harmonic beam in plasma with density ramp profile. The second harmonic undergoes periodic focusing in the plasma channel created by the fundamental wave. The normalized second harmonic amplitude varies periodically with distance and attains maximum value in the focal region. Enhancement in the second harmonic amplitude on account of relativistic self-focusing of laser based on plasma density transition is seen. Plasma density ramp plays an important role to make self-focusing stronger which leads to enhance the second harmonic generation in plasma.

Josephson plasma resonance in superconducting multilayers

DEFF Research Database (Denmark)

Pedersen, Niels Falsig; Sakai, S

1998-01-01

We derive an analytical solution for the Josephson plasma resonance of superconducting multilayers. This analytical solution is derived mainly for low-T-c systems with magnetic coupling between the superconducting layers. but many features of our results are more general, and thus an application...

Electron Cyclotron Resonance Heating of a High-Density Plasma

DEFF Research Database (Denmark)

Hansen, F. Ramskov

1986-01-01

Various schemes for electron cyclotron resonance heating of tokamak plasmas with the ratio of electron plasma frequency to electron cyclotron frequency, "»pe/^ce* larger than 1 on axis, are investigated. In particular, a mode conversion scheme is investigated using ordinary waves at the fundamental...... of the electron cyclotron frequency. These are injected obliquely from the outside of the tokamak near an optimal angle to the magnetic field lines. This method involves two mode conversions. The ordinary waves are converted into extraordinary waves near the plasma cut-off layer. The extraordinary waves...... are subsequently converted into electrostatic electron Bernstein waves at the upper hybrid resonance layer, and the Bernstein waves are completely absorbed close to the plasma centre. Results are presented from ray-tracinq calculations in full three-dimensional geometry using the dispersion function for a hot non...

Measurement of toroidal plasma current in RF heated helical plasmas

International Nuclear Information System (INIS)

Besshou, Sakae

1993-01-01

This report describes the measurement of toroidal plasma current by a semiflexible Rogowski coil in a helical vacuum chamber. A Rogowski coil measures the toroidal plasma current with a resolution of 0.1 kA, frequency range of up to 1 kHz and sensitivity of 6.5 x 10 -9 V · s/A. We measured the spontaneous toroidal plasma current (from -1.2 to +1.2 kA) under electron cyclotron resonance heating at 0.94 T toroidal field in the Heliotron-E device. We found that the measured direction of toroidal plasma current changes its sign as in the predicted behavior of a neoclassical diffusion-driven bootstrap current, depending on the horizontal position of the plasma column. We explain the observed plasma currents in terms of the compound phenomenon of an ohmic current and a neoclassical diffusion-driven current. The magnitude of the neoclassical current component is smaller than the value predicted by a collisionless neoclassical theory. (author)

Resonant heating of a cluster plasma by intense laser light

International Nuclear Information System (INIS)

Antonsen, Thomas M. Jr.; Taguchi, Toshihiro; Gupta, Ayush; Palastro, John; Milchberg, Howard M.

2005-01-01

Gases of atomic clusters are interaction media for laser pulse propagation with properties useful for applications such as extreme ultraviolet (EUV) and x-ray microscopy, harmonic generation, EUV lithography, and laser plasma acceleration. To understand cluster heating and expansion, a series of two- and three-dimensional electrostatic particle in cell simulations of the explosion of argon clusters of diameter in the range 20 nm-53 nm have been preformed. The studies show that heating is dominated by a nonlinear, resonant absorption process that gives rise to a size-dependent intensity threshold for strong absorption and that controls the dielectric properties of the cluster. Electrons are first accelerated out from the cluster and then driven back into it by the combined effects of the laser field and the electrostatic field produced by the laser-driven charge separation. Above the intensity threshold for strong heating there is a dramatic increase in the production of energetic particles and harmonic radiation. The dielectric properties of a gas of clusters are determined by the ensemble average cluster polarizability. Individual electrons contribute to the polarizability differently depending on whether they are in the core of the cluster or in the outer edge. Consequently, there can be large fluctuations in polarizability during the heating of a cluster

Spectroscopic measurements of plasma emission light for plasma-based acceleration experiments

International Nuclear Information System (INIS)

Filippi, F.; Mostacci, A.; Palumbo, L.; Anania, M.P.; Biagioni, A.; Chiadroni, E.; Ferrario, M.; Cianchi, A.; Zigler, A.

2016-01-01

Advanced particle accelerators are based on the excitation of large amplitude plasma waves driven by either electron or laser beams. Future experiments scheduled at the SPARC-LAB test facility aim to demonstrate the acceleration of high brightness electron beams through the so-called resonant Plasma Wakefield Acceleration scheme in which a train of electron bunches (drivers) resonantly excites wakefields into a preformed hydrogen plasma; the last bunch (witness) injected at the proper accelerating phase gains energy from the wake. The quality of the accelerated beam depends strongly on plasma density and its distribution along the acceleration length. The measurements of plasma density of the order of 10 16 –10 17  cm −3 can be performed with spectroscopic measurements of the plasma-emitted light. The measured density distribution for hydrogen filled capillary discharge with both Balmer alpha and Balmer beta lines and shot-to-shot variation are here reported.

Spectroscopic measurements of plasma emission light for plasma-based acceleration experiments

Science.gov (United States)

Filippi, F.; Anania, M. P.; Biagioni, A.; Chiadroni, E.; Cianchi, A.; Ferrario, M.; Mostacci, A.; Palumbo, L.; Zigler, A.

2016-09-01

Advanced particle accelerators are based on the excitation of large amplitude plasma waves driven by either electron or laser beams. Future experiments scheduled at the SPARC_LAB test facility aim to demonstrate the acceleration of high brightness electron beams through the so-called resonant Plasma Wakefield Acceleration scheme in which a train of electron bunches (drivers) resonantly excites wakefields into a preformed hydrogen plasma; the last bunch (witness) injected at the proper accelerating phase gains energy from the wake. The quality of the accelerated beam depends strongly on plasma density and its distribution along the acceleration length. The measurements of plasma density of the order of 1016-1017 cm-3 can be performed with spectroscopic measurements of the plasma-emitted light. The measured density distribution for hydrogen filled capillary discharge with both Balmer alpha and Balmer beta lines and shot-to-shot variation are here reported.

Energy confinement in JT-60 lower hybrid current driven plasmas

International Nuclear Information System (INIS)

Ushigusa, K.; Imai, T.; Naito, O.; Ikeda, Y.; Tsuji, S.; Uehara, K.

1990-01-01

The energy confinement in high power lower hybrid current driven (LHCD) plasmas has been studied in the JT-60 tokamak. At a plasma current of 1 MA, the diamagnetically estimated energy confinement time in LHCD plasmas has almost the same value as the confinement time in ohmically heated plasmas at n-bar e ∼ 1.0x10 19 m -3 . The confinement time of high power LHCD plasmas (P LH E varies as to P LH α n e β I p 0 with α + β ∼ -0.3. (author). Letter-to-the-editor. 12 refs, 5 figs

On the kinetic theory of parametric resonance in relativistic plasma

International Nuclear Information System (INIS)

El-Ashry, M.Y.

1982-08-01

The instability of relativistic hot plasma located in high-frequency external electric field is studied. The dispersion relation, in the case when the plasma electrons have relativistic oscillatory motion, is obtained. It is shown that if the electron Deby's radius is less than the wave length of plasma oscillation and far from the resonance on the overtones of the external field frequency, the oscillation build-up is possible. It is also shown that taking into account the relativistic motion of electrons leads to a considerable decrease in the frequency at which the parametric resonance takes place. (author)

Laboratory studies of the dynamic of resonance cones formation in magnetized plasmas

Energy Technology Data Exchange (ETDEWEB)

Nazarov, V. V.; Starodubtsev, M. V.; Kostrov, A. V. [Russian Academy of Sciences, Institute of Applied Physics, Nizhny Novgorod (Russian Federation)

2013-03-15

The paper is devoted to experimental studies of formation of resonance cones in magnetized plasmas by pulsed RF source in the lower-hybrid (whistler) and the upper-hybrid frequency ranges. It is shown that in both frequency ranges, resonance cones exhibit similar dynamics after switching-on the RF source: at first, wide maxima of radiation are formed in non-resonance directions, which then become narrower, with their direction approaching the resonance one. While the resonance cones are being formed, one observes a fine structure in the form of secondary radiation maxima. It is shown that the characteristic formation time of stationary resonance cones is determined by the minimal value of the group velocity of the quasi-electrostatic waves excited by the antenna. In the low-temperature plasma, this value is limited in the lower-hybrid frequency range by the spatial spectrum of the emitting antenna and in the upper-hybrid range, by the effects of spatial plasma dispersion.

An improved resonantly driven piezoelectric gas pump

International Nuclear Information System (INIS)

Wu, Yue; Liu, Yong; Liu, Jianfang; Jiao, Xiaoyang; Yang, Zhigang; Wang, Long

2013-01-01

Piezoelectric pumps have the potential to be used in a variety of applications, such as in air circulation and compression. However, piezoelectric membrane pumps do not have enough driving capacity, and the heat induced during the direct contact between the driving part and the gas medium cannot be dissipated smoothly. When the gas is blocked, the piezoelectric vibrator generates heat quickly, which may eventually lead to damage. Resonantly driven piezoelectric stack pumps have high performance but no price advantage. In this situation, a novel, resonantly driven piezoelectric gas pump with annular bimorph as the driver is presented. In the study, the working principle of the novel pump was analyzed, the vibration mechanics model was determined, and the displacement amplified theory was studied. The outcome indicates that the displacement amplification factor is related with the original displacement provided by the piezoelectric bimorph. In addition, the displacement amplification effect is related to the stiffness of the spring lamination, adjustment spring, and piezoelectric vibrator, as well as to the systematic damping factor and the driving frequency. The experimental prototypes of the proposed pump were designed, and the displacement amplification effect and gas output performance were measured. At 70 V of sinusoidal AC driving voltage, the improved pump amplified the piezoelectric vibrator displacement by 4.2 times, the maximum gas output flow rate reached 1685 ml/min, and the temperature of the bimorph remained normal after 2000 hours of operation when the gas medium was blocked.

Tilted spin torque-driven ferromagnetic resonance in a perpendicular-analyzer magnetic trilayer

International Nuclear Information System (INIS)

Wang Rixing; He Pengbin; Liu Quanhui; Li Zaidong; Pan Anlian; Zou Bingsuo; Wang Yanguo

2010-01-01

A theoretical study is presented on the current-driven ferromagnetic resonance in the magnetic trilayers. On the basis of the Landau-Lifshitz-Gilbert-Slonczewski equation, we derive the output dc voltage for arbitrary anisotropy in the free and pinned layers by the linearization method. As an example, the resonance spectra of the tilted-polarizer and perpendicular-analyzer trilayer show that the equilibrium position, the resonant linewidth and the resonant location can be tuned by changing the magnitude and the direction of spin torque. The effective damping can be minimized through adjusting the current and the pinned-layer magnetization direction.

Analytical investigation of microwave resonances of a curling probe for low and high-pressure plasma diagnostics

Science.gov (United States)

Arshadi, Ali; Brinkmann, Ralf Peter

2017-01-01

The concept of ‘active plasma resonance spectroscopy’ (APRS) has attracted greater interest in recent years as an established plasma diagnostic technique. The APRS describes a class of related methods utilizing the intrinsic ability of plasma to resonate at or near the electron plasma frequency {ω\\text{pe}} . The Curling probe (CP) as a novel realization of the APRS idea, is a miniaturized spiral slot embedded flatly in the chamber wall. Consequently, a plasma diagnostic technique with minimum disturbance and without metal contamination can be developed. To measure the plasma parameters the CP is fed with a weak frequency-swept signal from the exterior of the plasma chamber by a network analyzer which also records the response of the plasma versus the frequency. The resonance behavior is strongly dependent on the electron density and the gas pressure. The CP has also the advantage of resonating at a frequency greater than {ω\\text{pe}} which is dependent on the spiral’s length. The double resonance characteristic gives the CP the ability to be applied in varying plasma regimes. Assuming that the spiralization does not have a considerable effect on the resonances, a ‘straightened’ infinite length CP has recently been investigated (Arshadi and Brinkmann 2016 Plasma Sources Sci. Technol. 25 045014) to obtain the surface wave resonances. This work generalizes the approach and models the CP by a rectangular slot-type resonator located between plasma and quartz. Cold plasma theory and Maxwell’s equations are utilized to compute the electromagnetic fields propagating into the plasma by the diffraction of an incident plane wave at the slot. A mathematical model is employed and both kinds of resonances are derived. The analytical study of this paper shows good agreement with the numerical results of the probe inventors.

Structure of parallel-velocity-shear-driven mode in toroidal plasmas

International Nuclear Information System (INIS)

Dong, J.Q.; Xu, W.B.; Zhang, Y.Z.; Horton, W.

1998-01-01

It is shown that the Fourier-ballooning representation is appropriate for the study of short-wavelength drift-like perturbation in toroidal plasmas with a parallel velocity shear (PVS). The radial structure of the mode driven by a PVS is investigated in a torus. The Reynolds stress created by PVS turbulence, and proposed as one of the sources for a sheared poloidal plasma rotation, is analyzed. It is demonstrated that a finite ion temperature may strongly enhance the Reynolds stress creation ability from PVS-driven turbulence. The correlation of this observation with the requirement that ion heating power be higher than a threshold value for the formation of an internal transport barrier is discussed. copyright 1998 American Institute of Physics

Resonant and Ground Experimental Study on the Microwave Plasma Thruster

Science.gov (United States)

Yang, Juan; He, Hongqing; Mao, Genwang; Qu, Kun; Tang, Jinlan; Han, Xianwei

2002-01-01

chemistry. Therefore, the application of EP for the attitude control and station keeping of satellite, the propulsion of deep space exploration craft allows to reduce substantially the mass of on-board propellant and the launching cost. The EP research is now receiving high interest everywhere. microwave generating subsystem, the propellant supplying subsystem and the resonator (the thruster). Its principle is that the magnetron of the microwave generating subsystem transfers electric energy into microwave energy at given frequency which is introduced into a resonant cavity. Microwave will resonate within the cavity when it is adjusted. When the propellant gas (N2, Ar, He, NH3 or H2) is put into the cavity and coupled with microwave energy at the maximal electric intensity place, it will be broken down to form free-floating plasma, which flows from nozzle with high speed to produce thrust. Its characteristic is high efficiency, simple power supply and without electrode ablation, its specific impulse is greater than arcjet. 2450MHz, have been developed. The microwave generating subsystem and resonator of lower power MPT, 70-200W, are coaxial. The resonator with TEM resonating mode is section of coaxial wave-guide, of which one end is shorted, another is semi-opened. The maximal electric intensity field is in the lumped capacity formed between the end surface of inner conductor, retracting in the cavity, and the semi-opened surface of outer conductor. It provides favorable condition for gas breakdown. The microwave generating system and resonator of middle power MPT, 500-1,000W, are wave-guide cavity. The resonator with TM011 resonating mode is cylinder wave-guide cavity, of which two end surface are shorted. The distribution of electromagnetic field is axial symmetry, its maximal electric intensity field locates on the axis and closes to the exit of nozzle, where the propellant gas is breakdown to form free floating plasma. The plasma is free from the wall of

Nonlinear plasma waves excited near resonance

International Nuclear Information System (INIS)

Cohen, B.I.; Kaufman, A.N.

1977-01-01

The nonlinear resonant response of a uniform plasma to an external plane-wave field is formulated in terms of the mismatch Δ/sub n l/ between the driving frequency and the time-dependent, complex, nonlinear normal mode frequency at the driving wavenumber. This formalism is applied to computer simulations of this process, yielding a deduced nonlinear frequency shift. The time dependence of the nonlinear phenomena, at frequency Δ/sub n l/ and at the bounce frequency of the resonant particles, is analyzed. The interdependence of the nonlinear features is described by means of energy and momentum relations

Wave propagation near the lower hybrid resonance in toroidal plasmas

International Nuclear Information System (INIS)

Ohkubo, K.; Ohasa, K.; Matsuura, K.

1975-10-01

Dielectric tensor and equipotential curves (ray trajectories) of an electrostatic wave near the lower hybrid resonance are investigated for the toroidal plasma with a shear magnetic field. The ray trajectories start from the vicinity of the plasma surface, and rotate in a spiral form around the magnetic axis, and then reach the lower or upper parts of lower hybrid resonance layer. The numerical computations are performed on the parameters of JIPP T-II device with two dimensional inhomogeneity. (auth.)

Propagation of quasi-static wave and resonance cone in magnetized plasma

International Nuclear Information System (INIS)

Serbeto, A.P.B.

1980-08-01

The potential created by an oscillating punctual source in a magnetized homogeneous cold plasma, using quasistatic approximation is studied. The resonance cone structure in this plasma is theoretically obtained and it is verified that the conic field structure remains finite for an inhomogeneous cold plasma. The temperature effect in the resonance cone structure in layers where w->Ω e ,w->w PC and w->w nh for magnetized homogeneous electron plasma is studied. An approximated expression for dispersion relations is obtained, so that an analytical solution for the potential in these layers can be calculated. The theorem of energy conservation for quasistatic waves is developed. (M.C.K.) [pt

Evaluation of the toroidal torque driven by external non-resonant non-axisymmetric magnetic field perturbations in a tokamak

Energy Technology Data Exchange (ETDEWEB)

Kasilov, Sergei V. [Fusion@ÖAW, Institut für Theoretische Physik—Computational Physics, Technische Universität Graz Petersgasse 16, A–8010 Graz (Austria); Institute of Plasma Physics National Science Center “Kharkov Institute of Physics and Technology” ul. Akademicheskaya 1, 61108 Kharkov (Ukraine); Kernbichler, Winfried; Martitsch, Andreas F.; Heyn, Martin F. [Fusion@ÖAW, Institut für Theoretische Physik—Computational Physics, Technische Universität Graz Petersgasse 16, A–8010 Graz (Austria); Maassberg, Henning [Max-Planck Institut für Plasmaphysik, D-17491 Greifswald (Germany)

2014-09-15

The toroidal torque driven by external non-resonant magnetic perturbations (neoclassical toroidal viscosity) is an important momentum source affecting the toroidal plasma rotation in tokamaks. The well-known force-flux relation directly links this torque to the non-ambipolar neoclassical particle fluxes arising due to the violation of the toroidal symmetry of the magnetic field. Here, a quasilinear approach for the numerical computation of these fluxes is described, which reduces the dimension of a standard neoclassical transport problem by one without model simplifications of the linearized drift kinetic equation. The only limiting condition is that the non-axisymmetric perturbation field is small enough such that the effect of the perturbation field on particle motion within the flux surface is negligible. Therefore, in addition to most of the transport regimes described by the banana (bounce averaged) kinetic equation also such regimes as, e.g., ripple-plateau and resonant diffusion regimes are naturally included in this approach. Based on this approach, a quasilinear version of the code NEO-2 [W. Kernbichler et al., Plasma Fusion Res. 3, S1061 (2008).] has been developed and benchmarked against a few analytical and numerical models. Results from NEO-2 stay in good agreement with results from these models in their pertinent range of validity.

Curvature-driven instabilities in a hot-electron plasma: radial analysis

International Nuclear Information System (INIS)

Berk, H.L.; Van Dam, J.W.; Rosenbluth, M.N.; Spong, D.A.

1981-12-01

The theory of unfavorable curvature-driven instabilities is developed for a plasma interacting with a hot electron ring whose drift frequencies are larger than the growth rates predicted from conventional magnetohydrodynamic theory. A z-pinch model is used to emphasize the radial structure of the problem. Stability criteria are obtained for the five possible modes of instability: the conventional hot electron interchange, a high-frequency hot electron interchange (at frequencies larger than the ion cyclotron frequency), a compressional instability, a background pressure-driven interchange, and an interacting pressure-driven interchange

Linear and Nonlinear Response of a Rotating Tokamak Plasma to a Resonant Error-Field

Science.gov (United States)

Fitzpatrick, Richard

2014-10-01

An in-depth investigation of the effect of a resonant error-field on a rotating, quasi-cylindrical, tokamak plasma is preformed within the context of resistive-MHD theory. General expressions for the response of the plasma at the rational surface to the error-field are derived in both the linear and nonlinear regimes, and the extents of these regimes mapped out in parameter space. Torque-balance equations are also obtained in both regimes. These equations are used to determine the steady-state plasma rotation at the rational surface in the presence of the error-field. It is found that, provided the intrinsic plasma rotation is sufficiently large, the torque-balance equations possess dynamically stable low-rotation and high-rotation solution branches, separated by a forbidden band of dynamically unstable solutions. Moreover, bifurcations between the two stable solution branches are triggered as the amplitude of the error-field is varied. A low- to high-rotation bifurcation is invariably associated with a significant reduction in the width of the magnetic island chain driven at the rational surface, and vice versa. General expressions for the bifurcation thresholds are derived, and their domains of validity mapped out in parameter space. This research was funded by the U.S. Department of Energy under Contract DE-FG02-04ER-54742.

Josephson plasma resonance in vortex filament state of high temperature superconductors

International Nuclear Information System (INIS)

Matsuda, Yuji; Gaifullin, M.B.

1996-01-01

High temperature superconductors have the crystalline structure in which two-dimensional CuO 2 planes are piled in layers, consequently, the anisotropy of electroconductivity arises, and this brings about stable and low energy Josephson plasma in superconducting state. Also as to the vortex filament state of high temperature superconductors, the effect of thermal fluctuation due to low dimensionality, short coherence length and high transition temperature becomes conspicuous. In reality, these plasma and vortex filament state are related closely. Light reflection and plasma edge in superconducting state, Josephson plasma resonance in the vortex filament state of BiO 2 Sr 2 CaCu 2 O 8+δ , the plasma vibration in Josephson junction, Josephson plasma in magnetic field, Josephson plasma in the liquid state of vortex filament, Josephson plasma in the solid state of vortex filament, and Josephson plasma in parallel magnetic field are reported. The Josephson plasma resonance is the experimental means for exploring vortex filament state from microscopic standpoint, and its development hereafter is expected. (K.I.)

Chaves para ouvir Schumann (paralipomena à Kreisleriana - I

Directory of Open Access Journals (Sweden)

Leopoldo Waizbort

2006-07-01

Full Text Available Os paralipomena à "Kreisleriana" op. 16 de Robert Schumann (1810-1856 pretendem oferecer um espaço de indagações que circunscreva a obra e a insira em seu contexto. Informações sobre o compositor, seus círculos de sociabilidade e existência, assim como do ambiente no qual ele atua são mobilizadas tendo em vista caracterizar a obra de arte musical e permitir uma primeira aproximação à fatura complexa da obra e seus variados aspectos, elementos e condicionantes. O texto é parte de um estudo mais amplo, ainda incompleto.The paralipomena to Robert Schumann’s "Kreisleriana" op. 16 raise questions concerning this piece and its historical and social context. Information about the composer and his social environment is gathered in order to characterize the musical work of art and allow a first approach to the complex elements that interfere on its making. The text is part of a broader study, still unfinished.

(Electro-) mechanical characteristics of electrostatically driven vacuum encapsulated polysilicon resonators

NARCIS (Netherlands)

Tilmans, H.A.C.; Tilmans, H.A.C.; Legtenberg, Rob; Legtenberg, R.; Schurer, H.; Schurer, H.; IJntema, D.J.; Ijntema, D.J.; Elwenspoek, Michael Curt; Fluitman, J.H.J.

The design, fabrication and performance of vacuum-encapsulated electrostatically driven polysilicon resonating beams, 210-510 μm long, 100 μm wide, and 1.5 μm thick, are described. The shortest beams have a fundamental frequency of 324 kHz, a gauge factor of 2400 and a quality factor of 600 at

Robert Schumann and translation: poetic creativity, simultaneity and movement

Directory of Open Access Journals (Sweden)

João Azenha Junior

2012-07-01

Full Text Available In diesem Aufsatz werden die Gesammelten Schriften über Musik und Musiker von Robert Schumann untersucht, insbesondere die Rezensionen, die der Komponist zwischen 1834 und 1836 verfasst hat. Es soll festgestellt werden, inwiefern sich darin die wichtigsten Auffassungen über Sprache und Übersetzung, die Ende des 18. und Beginn des 19. Jahrhunderts in Deutschland entstanden, wiederfinden. Im Vordergrund der Untersuchung steht die Dimension der Bewegung, die sich sowohl im Individuum als auch in der Zeit festmachen lässt. Im Individuum manifestiert sich die Bewegung als ein sehr persönlicher Vorgang, da es sich innerhalb verschiedener Zeichensysteme bewegt, die seine Gedanken ausdrücken; oder aber es bewegt sich innerhalb verschiedener Sprachen. Die Zeitdimension wiederum bedeutet, in ein Umfeld einzutauchen, das die Zeitbarrieren überwindet und die Vergangenheit auf einen Schlag mit der Gegenwart und der Zukunft verbindet.

Introduction of fusion driven subcritical system plasma design

International Nuclear Information System (INIS)

Bin Wu

2003-01-01

Fusion driven subcritical nuclear system (FDS) is a multifunctional hybrid reactor, which could breed nuclear fuel, transmute long-lived wastes, producing tritium and so on. This paper presents an introduction of FDS plasma design. Several different advance equilibrium configurations have been proposed and a 1.5-D discharge simulation of FDS was also present

Breathing-mode resonance of a complex plasma disk

International Nuclear Information System (INIS)

Sheridan, T.E.; Buckey, C.R.; Cox, D.J.; Merrill, R.J.; Theisen, W.L.

2004-01-01

We have experimentally characterized the breathing mode oscillation of a strongly-coupled, dusty plasma disk. Steady-state oscillations are excited by sinusoidally modulating the plasma density, creating a single-frequency, in-plane driving force. Resonance curves agree well with damped harmonic oscillator theory. A response at the second harmonic is observed and found to increase with the square of the driving force, indicating a quadratic nonlinearity

Electron Parametric Instabilities Driven by Relativistically Intense Laser Light in Plasma

Science.gov (United States)

Barr, H. C.; Mason, P.; Parr, D. M.

1999-08-01

A unified treatment of electron parametric instabilities driven by ultraintense laser light in plasma is described. It is valid for any intensity, polarization, plasma density, and scattering geometry. The method is applied to linearly polarized light in both underdense plasma and overdense plasma accessible by self-induced transparency. New options arise which are hybrids of stimulated Raman scattering, the two plasmon decay, the relativistic modulational and filamentation instabilities, and stimulated harmonic generation. There is vigorous growth over a wide range of wave numbers and harmonics.

Resonant power absorption in helicon plasma sources

International Nuclear Information System (INIS)

Chen Guangye; Arefiev, Alexey V.; Bengtson, Roger D.; Breizman, Boris N.; Lee, Charles A.; Raja, Laxminarayan L.

2006-01-01

Helicon discharges produce plasmas with a density gradient across the confining magnetic field. Such plasmas can create a radial potential well for nonaxisymmetric whistlers, allowing radially localized helicon (RLH) waves. This work presents new evidence that RLH waves play a significant role in helicon plasma sources. An experimentally measured plasma density profile in an argon helicon discharge is used to calculate the rf field structure. The calculations are performed using a two-dimensional field solver under the assumption that the density profile is axisymmetric. It is found that RLH waves with an azimuthal wave number m=1 form a standing wave structure in the axial direction and that the frequency of the RLH eigenmode is close to the driving frequency of the rf antenna. The calculated resonant power absorption, associated with the RLH eigenmode, accounts for most of the rf power deposited into the plasma in the experiment

Soliton Coupling Driven by Phase Fluctuations in Auto-Parametric Resonance

CERN Document Server

Binder, B

2002-01-01

In this paper the interaction of sine-Gordon solitons and mediating linear waves is modelled by a special case of auto-parametric resonance, the Rayleigh-type self-excited non-linear autonomous system driven by a statistical phase gradient related to the soliton energy. Spherical symmetry can stimulate "whispering gallery modes" (WGM) with integral coupling number M=137.

Development of a plasma driven permeation experiment for TPE

Energy Technology Data Exchange (ETDEWEB)

Buchenauer, Dean, E-mail: dabuche@sandia.gov [Sandia National Laboratories, Livermore, CA (United States); Kolasinski, Robert [Sandia National Laboratories, Livermore, CA (United States); Shimada, Masa [Idaho National Laboratory, Idaho Falls, ID (United States); Donovan, David [Sandia National Laboratories, Livermore, CA (United States); Youchison, Dennis [Sandia National Laboratories, Albuquerque, NM (United States); Merrill, Brad [Idaho National Laboratory, Idaho Falls, ID (United States)

2014-10-15

Highlights: • We have designed and fabricated a novel tritium permeation membrane holder for use in the Tritium Plasma Experiment (TPE). • The membrane temperature is controlled by varying the cooling flow rate and proximity of a spiral cooling channel. • Sealing tests have demonstrated adequate helium leak rates up to temperatures of 1000 °C. • Flow modeling indicates a minimal helium pressure drop across the membrane holder (<700 Pa). • Thermal modeling shows good heat removal and minimal membrane temperature variation (±2%) even up to peak TPE ion fluxes. - Abstract: Experiments on retention of hydrogen isotopes (including tritium) at temperatures less than 800 °C have been carried out in the Tritium Plasma Experiment (TPE) at Idaho National Laboratory [1,2]. To provide a direct measurement of plasma driven permeation in plasma facing materials at temperatures reaching 1000 °C, a new TPE membrane holder has been built to hold test specimens (≤1 mm in thickness) at high temperature while measuring tritium permeating through the membrane from the plasma facing side. This measurement is accomplished by employing a carrier gas that transports the permeating tritium from the backside of the membrane to ion chambers giving a direct measurement of the plasma driven tritium permeation rate. Isolation of the membrane cooling and sweep gases from TPE's vacuum chamber has been demonstrated by sealing tests performed up to 1000 °C of a membrane holder design that provides easy change out of membrane specimens between tests. Simulations of the helium carrier gas which transports tritium to the ion chamber indicate a very small pressure drop (∼700 Pa) with good flow uniformity (at 1000 sccm). Thermal transport simulations indicate that temperatures up to 1000 °C are expected at the highest TPE fluxes.

Development of a plasma driven permeation experiment for TPE

International Nuclear Information System (INIS)

Buchenauer, Dean; Kolasinski, Robert; Shimada, Masa; Donovan, David; Youchison, Dennis; Merrill, Brad

2014-01-01

Highlights: • We have designed and fabricated a novel tritium permeation membrane holder for use in the Tritium Plasma Experiment (TPE). • The membrane temperature is controlled by varying the cooling flow rate and proximity of a spiral cooling channel. • Sealing tests have demonstrated adequate helium leak rates up to temperatures of 1000 °C. • Flow modeling indicates a minimal helium pressure drop across the membrane holder (<700 Pa). • Thermal modeling shows good heat removal and minimal membrane temperature variation (±2%) even up to peak TPE ion fluxes. - Abstract: Experiments on retention of hydrogen isotopes (including tritium) at temperatures less than 800 °C have been carried out in the Tritium Plasma Experiment (TPE) at Idaho National Laboratory [1,2]. To provide a direct measurement of plasma driven permeation in plasma facing materials at temperatures reaching 1000 °C, a new TPE membrane holder has been built to hold test specimens (≤1 mm in thickness) at high temperature while measuring tritium permeating through the membrane from the plasma facing side. This measurement is accomplished by employing a carrier gas that transports the permeating tritium from the backside of the membrane to ion chambers giving a direct measurement of the plasma driven tritium permeation rate. Isolation of the membrane cooling and sweep gases from TPE's vacuum chamber has been demonstrated by sealing tests performed up to 1000 °C of a membrane holder design that provides easy change out of membrane specimens between tests. Simulations of the helium carrier gas which transports tritium to the ion chamber indicate a very small pressure drop (∼700 Pa) with good flow uniformity (at 1000 sccm). Thermal transport simulations indicate that temperatures up to 1000 °C are expected at the highest TPE fluxes

Nonlinear resonance and dynamical chaos in a diatomic molecule driven by a resonant ir field

International Nuclear Information System (INIS)

Berman, G.P.; Bulgakov, E.N.; Holm, D.D.

1995-01-01

We consider the transition from regular motion to dynamical chaos in a classical model of a diatomic molecule which is driven by a circularly polarized resonant ir field. Under the conditions of a nearly two-dimensional case, the Hamiltonian reduces to that for the nonintegrable motion of a charged particle in an electromagnetic wave [A. J. Lichtenberg and M. A. Lieberman, Regular and Stochastic Motion (Springer-Verlag, City, 1983)]. In the general case, the transition to chaos is connected with the overlapping of vibrational-rotational nonlinear resonances and appears even at rather low radiation field intensity, S approx-gt 1 GW/cm 2 . We also discuss the possibility of experimentally observing this transition

Gyrokinetic theory of perpendicular cyclotron resonance in a nonuniformly magnetized plasma

International Nuclear Information System (INIS)

Lashmore-Davies, C.N.; Dendy, R.O.

1989-01-01

The extension of gyrokinetic theory to arbitrary frequencies by Chen and Tsai [Phys. Fluids 26, 141 (1983); Plasma Phys. 25, 349 (1983)] is used to study cyclotron absorption in a straight magnetic field with a perpendicular, linear gradient in strength. The analysis includes the effects of magnetic field variation across the Larmor orbit and is restricted to propagation perpendicular to the field. It yields the following results for propagation into the field gradient. The standard optical depths for the fundamental O-mode and second harmonic X-mode resonances are obtained from the absorption profiles given in this paper, without invoking relativistic mass variation [see also Antonsen and Manheimer, Phys. Fluids 21, 2295 (1978)]. The compressional Alfven wave is shown to undergo perpendicular cyclotron damping at the fundamental minority resonance in a two-ion species plasma and at second harmonic resonance in a single-ion species plasma. Ion Bernstein waves propagating into the second harmonic resonance are no longer unattenuated, but are increasingly damped as they approach the resonance. It is shown how the kinetic power flow affects absorption profiles, yielding information previously obtainable only from full-wave theory. In all cases, the perpendicular cyclotron damping arises from the inclusion of magnetic field variation across the Larmor orbit

MM-wave cyclotron auto-resonance maser for plasma heating

Science.gov (United States)

Ceccuzzi, S.; Dattoli, G.; Di Palma, E.; Doria, A.; Gallerano, G. P.; Giovenale, E.; Mirizzi, F.; Spassovsky, I.; Ravera, G. L.; Surrenti, V.; Tuccillo, A. A.

2014-02-01

Heating and Current Drive systems are of outstanding relevance in fusion plasmas, magnetically confined in tokamak devices, as they provide the tools to reach, sustain and control burning conditions. Heating systems based on the electron cyclotron resonance (ECRH) have been extensively exploited on past and present machines DEMO, and the future reactor will require high frequencies. Therefore, high power (≥1MW) RF sources with output frequency in the 200 - 300 GHz range would be necessary. A promising source is the so called Cyclotron Auto-Resonance Maser (CARM). Preliminary results of the conceptual design of a CARM device for plasma heating, carried out at ENEA-Frascati will be presented together with the planned R&D development.

Non-stationarity of resonance signals from magnetospheric and ionospheric plasmas

International Nuclear Information System (INIS)

Higel, Bernard

1975-01-01

Rocket observations of resonance signals from ionospheric plasma were made during EIDI relaxation sounding experiments. It appeared that their amplitude, phase, and frequency characteristics are not stationary as a function of the receipt time. The measurement of these nonstationary signals increases the interest presented by resonance phenomena in spatial plasma diagnostics, but this measurement is not easy for frequency non-stationarities. A new method, entirely numerical, is proposed for automatic recognition of these signals. It will be used for the selecting and real-time processing of signals of the same type to be observed during relaxation sounding experiments on board of the futur GEOS satellite. In this method a statistical discrimination is done on the values taken by several parameters associated with the non-stationarities of the observed resonance signals [fr

High-quality electron beam generation in a proton-driven hollow plasma wakefield accelerator

Science.gov (United States)

Li, Y.; Xia, G.; Lotov, K. V.; Sosedkin, A. P.; Hanahoe, K.; Mete-Apsimon, O.

2017-10-01

Simulations of proton-driven plasma wakefield accelerators have demonstrated substantially higher accelerating gradients compared to conventional accelerators and the viability of accelerating electrons to the energy frontier in a single plasma stage. However, due to the strong intrinsic transverse fields varying both radially and in time, the witness beam quality is still far from suitable for practical application in future colliders. Here we demonstrate the efficient acceleration of electrons in proton-driven wakefields in a hollow plasma channel. In this regime, the witness bunch is positioned in the region with a strong accelerating field, free from plasma electrons and ions. We show that the electron beam carrying the charge of about 10% of 1 TeV proton driver charge can be accelerated to 0.6 TeV with a preserved normalized emittance in a single channel of 700 m. This high-quality and high-charge beam may pave the way for the development of future plasma-based energy frontier colliders.

Femtosecond envelope of the high-harmonic emission from ablation plasmas

International Nuclear Information System (INIS)

Haessler, S; Gobert, O; Hergott, J-F; Lepetit, F; Perdrix, M; Carré, B; Salières, P; Bom, L B Elouga; Ozaki, T

2012-01-01

We characterize the temporal profile of the high-order harmonic emission from ablation plasma plumes using cross-correlations with the infrared (IR) laser beam provided by two-photon harmonic+IR ionization of rare gas atoms. We study both non-resonant plasmas (lead, gold and chrome) and resonant plasmas (indium and tin), i.e. plasmas presenting in the singly charged ions a strong radiative transition coinciding with a harmonic order. The cross-correlation traces are found to be very similar for all harmonic orders and all plasma targets. The recovered harmonic pulse durations are very similar to the driving laser, with a tendency towards being shorter, demonstrating that the emission is a directly laser-driven process even in the case of resonant harmonics. This provides a valuable input for theories describing resonant-harmonic emission and opens the perspective of a very high flux tabletop XUV source for applications. (paper)

Solar flux variability in the Schumann-Runge continuum as a function of solar cycle 21

International Nuclear Information System (INIS)

Torr, M.R.; Torr, D.G.; Hinteregger, H.E.

1980-01-01

Measurements of the solar flux in the Schumann-Runge continuum (1350-1750 A) by the Atmosphere Explorer satellites reveal a strong dependence on solar activity. Solar intensities over the rising phase of cycle 21, increase by more than a factor of two at the shorter wavelengths (1350 A), with a smaller change (approx.10%) at 1750 A. A significant 27 day variability is found to exist superimposed on the solar cycle variation. Because radiation in this portion of the spectum is important to the lower thermosphere in the photodissociation of 0 2 and the production of 0( 1 D), we use the unattenuated Schumann-Runge continuum dissociation frequency as a parameter to illustrate the magnitude and temporal characteristics of this variation. The values of this parameter, J/sub infinity/(0 2 )/sub SR/, range from 1.5 x 10 -6 s -1 for April 23, 1974, to 2.8 x 10 -6 s -1 for February 19, 1979. In studies of oxygen in the lower thermosphere, it is therefore necessary to use solar spectral intensities representative of the actual conditions for which the calculations are made. Both the J/sub infinity/(0 2 )/sub SR/ parameter and the solar flux at various wavelengths over the 1350 to 1750 A range can be expressed in terms of the F10.7 index to a reasonable approximation

Resonant charge exchange for H-H+ in Debye plasmas

Science.gov (United States)

Laricchiuta, Annarita; Colonna, Gianpiero; Capitelli, Mario; Kosarim, Alexander; Smirnov, Boris M.

2017-11-01

The dynamics of resonant charge exchange in proton-hydrogen collisions embedded in plasma is investigated in the framework of the asymptotic approach, modified to account for the effect of Debye-Hückel screening in particle interactions. The cross sections exhibit a marked dependence on the Debye length in regimes of severe plasma confinement. Processes involving excited states H( n)-H+ are also discussed.

Isotope separation in plasma by ion-cyclotron resonance method

International Nuclear Information System (INIS)

Dubinov, A.E.; Kornilova, I.Yu.; Selemir, V.D.

2001-01-01

Contemporary state of investigation on isotope separation in plasma using selective ion-cyclotron resonance (ICR) heating is considered. The main attention is paid to necessary conditions of heating selectivity, plasma creation methods in isotope ICR-separation facilities, selection of antenna systems for heating, and principles of more-heated component selection. Experimental results obtained at different isotope mixtures separation are presented [ru

Pre-Excitation Studies for Rubidium-Plasma Generation

CERN Document Server

Aladi, M; Barna, I.F.; Czitrovszky, Aladar; Djotyan, Gagik; Dombi, Peter; Dzsotjan, David; FöLdes, Istvan; Hamar, Gergo; Ignacz, Peter; Kedves, Miklos; Kerekes, Attila; Levai, Peter; Marton, Istvan; Nagy, Attila; Oszetzky, Daniel; Pocsai, Mihaly; Racz, Peter; Raczkevi, Bela; Szigeti, Janos; Sörlei, Zsuzsa; Szipöcs, Robert; Varga, Dezso; Varga-Umbrich, Karoly; Varro, Sandor; Vamos, Lenard; Vesztergombi, György

2014-01-01

The key element in the Proton-Driven-Plasma-Wake-Field-Accelerator (AWAKE) project is the generation of highly uniform plasma from Rubidium vapor. The standard way to achieve full ionization is to use high power laser which can assure the over-barrier-ionization (OBI) along the 10 meters long active region. The Wigner-team in Budapest is investigating an alternative way of uniform plasma generation. The proposed Resonance Enhanced Multi Photon Ionization (REMPI) scheme probably can be realized by much less laser power. In the following the resonant pre-excitations of the Rb atoms are investigated, theoretically and the status report about the preparatory work on the experiment are presented.

Nonlinear Right-Hand Polarized Wave in Plasma in the Electron Cyclotron Resonance Region

Science.gov (United States)

Krasovitskiy, V. B.; Turikov, V. A.

2018-05-01

The propagation of a nonlinear right-hand polarized wave along an external magnetic field in subcritical plasma in the electron cyclotron resonance region is studied using numerical simulations. It is shown that a small-amplitude plasma wave excited in low-density plasma is unstable against modulation instability with a modulation period equal to the wavelength of the excited wave. The modulation amplitude in this case increases with decreasing detuning from the resonance frequency. The simulations have shown that, for large-amplitude waves of the laser frequency range propagating in plasma in a superstrong magnetic field, the maximum amplitude of the excited longitudinal electric field increases with the increasing external magnetic field and can reach 30% of the initial amplitude of the electric field in the laser wave. In this case, the energy of plasma electrons begins to substantially increase already at magnetic fields significantly lower than the resonance value. The laser energy transferred to plasma electrons in a strong external magnetic field is found to increase severalfold compared to that in isotropic plasma. It is shown that this mechanism of laser radiation absorption depends only slightly on the electron temperature.

Emission of electromagnetic radiation from beam driven plasmas

International Nuclear Information System (INIS)

Newman, D.L.

1985-01-01

Two production mechanisms for electromagnetic radiation from a plasma containing electron-beam-driven weak Langmuir turbulence are studied: induced Compton conversion and two-Langmuir-wave coalescence. Induced Compton conversion in which a Langmuir wave scatters off a relativistic electron while converting into a transversely polarized electromagnetic wave is considered as a means for producing amplified electromagnetic radiation from a beam-plasma system at frequencies well above the electron plasma frequency. The induced emission growth rates of the radiation produced by a monoenergetic ultrarelativistic electron beam are determined as a function of the Langmuir turbulence spectrum in the background plasma and are numerically evaluated for a range of model Langmuir spectra. Induced Compton conversion can play a role in emission from astrophysical beam-plasma systems if the electron beam is highly relativistic and sufficiently narrow. However, it is found that the growth rates for this process are too small in all cases studied to account for the intense high-frequency radiation observed in laboratory experiments. Two-Langmuir-wave coalescence as a means of producing radiation at 2omega/sub p/ is investigated in the setting of the earth's foreshock

Autler-Townes effect in a strongly driven electromagnetically induced transparency resonance

International Nuclear Information System (INIS)

Yang Lijun; Zhang Lianshui; Li Xiaoli; Han Li; Fu Guangsheng; Manson, Neil B.; Suter, Dieter; Wei Changjiang

2005-01-01

In this paper we study the nonlinear behavior of an electromagnetically induced transparency (EIT) resonance subject to a coherent driving field. The EIT is associated with a Λ three-level system where two hyperfine levels within an electronic ground state are coupled to a common excited state level by a coupling field and a probe field. In addition there is an radio-frequency (rf) field driving a hyperfine transition within the ground state. The paper contrasts two different situations. In one case the rf-driven transition shares a common level with the probed transition and in the second case it shares a common level with the coupled transition. In both cases the EIT resonance is split into a doublet and the characteristics of the EIT doublet are determined by the strength and frequency of the rf-driving field. The doublet splitting originates from the rf-field induced dynamic Stark effect and has close analogy with the Autler-Townes effect observed in three-level pump-probe spectroscopy study. The situation changes when the rf field is strong and the two cases are very different. One is analogous to two Λ three-level systems with EIT resonance associated with each. The other corresponds to a doubly driven three-level system with rf-field-induced electromagnetically induced absorption resonance. The two situations are modeled using numerical solutions of the relevant equation of motion of density matrix. In addition a physical account of their behaviors is given in terms of a dressed state picture

Modification of Plasma Solitons by Resonant Particles

DEFF Research Database (Denmark)

Karpman, Vladimir; Lynov, Jens-Peter; Michelsen, Poul

1980-01-01

A consistent theory of plasma soliton interaction with resonant particles is developed. A simple derivation of a perturbed Korteweg–de Vries equation with the interaction term is presented. It is shown how the known limit cases (such as Ott–Sudan’s, etc.) can be derived from the general equations...... Korteweg–de Vries equation. Laboratory measurements carried out in a strongly magnetized, plasma‐filled waveguide and results from particle simulation are interpreted in terms of the analytical results.......A consistent theory of plasma soliton interaction with resonant particles is developed. A simple derivation of a perturbed Korteweg–de Vries equation with the interaction term is presented. It is shown how the known limit cases (such as Ott–Sudan’s, etc.) can be derived from the general equations...... and what their regions of applicability are. Some effects caused by the soliton‐particle interaction (amplitude change‐rate, tail formation, etc.) are analyzed by means of a recently developed perturbation method. The analytical results are compared with a direct numerical integration of the perturbed...

Proton-driven plasma wakefield acceleration: a path to the future of high-energy particle physics

International Nuclear Information System (INIS)

Assmann, R; Gross, M; Bingham, R; Holloway, J; Bohl, T; Bracco, C; Butterworth, A; Feldbaumer, E; Goddard, B; Gschwendtner, E; Buttenschön, B; Caldwell, A; Chattopadhyay, S; Cipiccia, S; Jaroszynski, D; Fonseca, R A; Grulke, O; Kempkes, P; Huang, C; Jolly, S

2014-01-01

New acceleration technology is mandatory for the future elucidation of fundamental particles and their interactions. A promising approach is to exploit the properties of plasmas. Past research has focused on creating large-amplitude plasma waves by injecting an intense laser pulse or an electron bunch into the plasma. However, the maximum energy gain of electrons accelerated in a single plasma stage is limited by the energy of the driver. Proton bunches are the most promising drivers of wakefields to accelerate electrons to the TeV energy scale in a single stage. An experimental program at CERN—the AWAKE experiment—has been launched to study in detail the important physical processes and to demonstrate the power of proton-driven plasma wakefield acceleration. Here we review the physical principles and some experimental considerations for a future proton-driven plasma wakefield accelerator. (paper)

Proton-driven plasma wakefield acceleration: a path to the future of high-energy particle physics

CERN Document Server

Assmann, R.; Bohl, T.; Bracco, C.; Buttenschon, B.; Butterworth, A.; Caldwell, A.; Chattopadhyay, S.; Cipiccia, S.; Feldbaumer, E.; Fonseca, R.A.; Goddard, B.; Gross, M.; Grulke, O.; Gschwendtner, E.; Holloway, J.; Huang, C.; Jaroszynski, D.; Jolly, S.; Kempkes, P.; Lopes, N.; Lotov, K.; Machacek, J.; Mandry, S.R.; McKenzie, J.W.; Meddahi, M.; Militsyn, B.L.; Moschuering, N.; Muggli, P.; Najmudin, Z.; Noakes, T.C.Q.; Norreys, P.A.; Oz, E.; Pardons, A.; Petrenko, A.; Pukhov, A.; Rieger, K.; Reimann, O.; Ruhl, H.; Shaposhnikova, E.; Silva, L.O.; Sosedkin, A.; Tarkeshian, R.; Trines, R.M.G.N.; Tuckmantel, T.; Vieira, J.; Vincke, H.; Wing, M.; Xia, G.

2014-01-01

New acceleration technology is mandatory for the future elucidation of fundamental particles and their interactions. A promising approach is to exploit the properties of plasmas. Past research has focused on creating large-amplitude plasma waves by injecting an intense laser pulse or an electron bunch into the plasma. However, the maximum energy gain of electrons accelerated in a single plasma stage is limited by the energy of the driver. Proton bunches are the most promising drivers of wakefields to accelerate electrons to the TeV energy scale in a single stage. An experimental program at CERN -- the AWAKE experiment -- has been launched to study in detail the important physical processes and to demonstrate the power of proton-driven plasma wakefield acceleration. Here we review the physical principles and some experimental considerations for a future proton-driven plasma wakefield accelerator.

Characterization of electron cyclotron resonance hydrogen plasmas

International Nuclear Information System (INIS)

Outten, C.A.

1990-01-01

Electron cyclotron resonance (ECR) plasmas yield low energy and high ion density plasmas. The characteristics downstream of an ECR hydrogen plasma were investigated as a function of microwave power and magnetic field. A fast-injection Langmuir probe and a carbon resistance probe were used to determine plasma potential (V p ), electron density (N e ), electron temperature (T e ), ion energy (T i ), and ion fluence. Langmuir probe results showed that at 17 cm downstream from the ECR chamber the plasma characteristics are approximately constant across the center 7 cm of the plasma for 50 Watts of absorbed power. These results gave V p = 30 ± 5 eV, N e = 1 x 10 8 cm -3 , and T e = 10--13 eV. In good agreement with the Langmuir probe results, carbon resistance probes have shown that T i ≤ 50 eV. Also, based on hydrogen chemical sputtering of carbon, the hydrogen (ion and energetic neutrals) fluence rate was determined to be 1 x 10 16 /cm 2 -sec. at a pressure of 1 x 10 -4 Torr and for 50 Watts of absorbed power. 19 refs

Editorial: Focus on Laser- and Beam-Driven Plasma Accelerators

Science.gov (United States)

Joshi, Chan; Malka, Victor

2010-04-01

The ability of short but intense laser pulses to generate high-energy electrons and ions from gaseous and solid targets has been well known since the early days of the laser fusion program. However, during the past decade there has been an explosion of experimental and theoretical activity in this area of laser-matter interaction, driven by the prospect of realizing table-top plasma accelerators for research, medical and industrial uses, and also relatively small and inexpensive plasma accelerators for high-energy physics at the frontier of particle physics. In this focus issue on laser- and beam-driven plasma accelerators, the latest advances in this field are described. Focus on Laser- and Beam-Driven Plasma Accelerators Contents Slow wave plasma structures for direct electron acceleration B D Layer, J P Palastro, A G York, T M Antonsen and H M Milchberg Cold injection for electron wakefield acceleration X Davoine, A Beck, A Lifschitz, V Malka and E Lefebvre Enhanced proton flux in the MeV range by defocused laser irradiation J S Green, D C Carroll, C Brenner, B Dromey, P S Foster, S Kar, Y T Li, K Markey, P McKenna, D Neely, A P L Robinson, M J V Streeter, M Tolley, C-G Wahlström, M H Xu and M Zepf Dose-dependent biological damage of tumour cells by laser-accelerated proton beams S D Kraft, C Richter, K Zeil, M Baumann, E Beyreuther, S Bock, M Bussmann, T E Cowan, Y Dammene, W Enghardt, U Helbig, L Karsch, T Kluge, L Laschinsky, E Lessmann, J Metzkes, D Naumburger, R Sauerbrey, M. Scḧrer, M Sobiella, J Woithe, U Schramm and J Pawelke The optimum plasma density for plasma wakefield excitation in the blowout regime W Lu, W An, M Zhou, C Joshi, C Huang and W B Mori Plasma wakefield acceleration experiments at FACET M J Hogan, T O Raubenheimer, A Seryi, P Muggli, T Katsouleas, C Huang, W Lu, W An, K A Marsh, W B Mori, C E Clayton and C Joshi Electron trapping and acceleration on a downward density ramp: a two-stage approach R M G M Trines, R Bingham, Z Najmudin

Bifurcated states of a rotating tokamak plasma in the presence of a static error-field

International Nuclear Information System (INIS)

Fitzpatrick, R.

1998-01-01

The bifurcated states of a rotating tokamak plasma in the presence of a static, resonant, error-field are strongly analogous to the bifurcated states of a conventional induction motor. The two plasma states are the open-quotes unreconnectedclose quotes state, in which the plasma rotates and error-field-driven magnetic reconnection is suppressed, and the open-quotes fully reconnectedclose quotes state, in which the plasma rotation at the rational surface is arrested and driven magnetic reconnection proceeds without hindrance. The response regime of a rotating tokamak plasma in the vicinity of the rational surface to a static, resonant, error-field is determined by three parameters: the normalized plasma viscosity, P, the normalized plasma rotation, Q 0 , and the normalized plasma resistivity, R. There are 11 distinguishable response regimes. The extents of these regimes are calculated in P endash Q 0 endash R space. In addition, an expression for the critical error-field amplitude required to trigger a bifurcation from the open-quotes unreconnectedclose quotes to the open-quotes fully reconnectedclose quotes state is obtained in each regime. The appropriate response regime for low-density, ohmically heated, tokamak plasmas is found to be the nonlinear constant-ψ regime for small tokamaks, and the linear constant-ψ regime for large tokamaks. The critical error-field amplitude required to trigger error-field-driven magnetic reconnection in such plasmas is a rapidly decreasing function of machine size, indicating that particular care may be needed to be taken to reduce resonant error-fields in a reactor-sized tokamak. copyright 1998 American Institute of Physics

Optical field emission from resonant gold nanorods driven by femtosecond mid-infrared pulses

Energy Technology Data Exchange (ETDEWEB)

Kusa, F. [Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei Tokyo 184-8588 (Japan); Institute of Industrial Science, the University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Echternkamp, K. E.; Herink, G.; Ropers, C. [4th Physical Institute – Solids and Nanostructures, University of Göttingen, 37077 Göttingen (Germany); Ashihara, S., E-mail: ashihara@iis.u-tokyo.ac.jp [Institute of Industrial Science, the University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

2015-07-15

We demonstrate strong-field photoelectron emission from gold nanorods driven by femtosecond mid-infrared optical pulses. The maximum photoelectron yield is reached at the localized surface plasmon resonance, indicating that the photoemission is governed by the resonantly-enhanced optical near-field. The wavelength- and field-dependent photoemission yield allows for a noninvasive determination of local field enhancements, and we obtain intensity enhancement factors close to 1300, in good agreement with finite-difference time domain computations.

Stability aspects of plasmas penetrated by neutral gas with respect to velocity driven modes

International Nuclear Information System (INIS)

Ohlsson, D.

1978-08-01

A study of the stability properties of dense partially ionized plasmas immersed in strong magnetic fields with respect to velocity driven modes are presented. First we consider modes driven by mass motion perpendicular to the lines of force and the unperturbed density and temperature gradients. The presence of a third fluid, neutral gas, gives under certain conditions rise to unstable modes. This type of instability arises independently or whether the applied electric field transverse to the lines of force, driving the mass motion, being parallel or antiparallel to the unperturbed density and temperature gradient. The presence of neutral gas also corresponds to stabilizing effects which, in certain parameter regions, result in a quenching of this instability. It is shown that modes driven by velocity shear perpendicular to the lines of force are effectively stabilized by viscous and resistive effects. These effects are in certain parameter ranges strongly enhanced on account of plasma-neutral gas interaction effects. In collisionless plasmas, modes driven by velocity shear parallel to the lines of force are stabilized by compressibility effects parallel to the magnetic field and by finite Larmor radius effects. (author)

Plasma equilibrium profiles with applied resonant fields on TBR-1 tokamak

International Nuclear Information System (INIS)

Castro, R.M. de; Heller, M.V.A.P.; Caldas, I.L.; Silva, R.P. da; Brasilio, Z.A.; Oda, G.A.

1995-01-01

In this work we present the measurements of the plasma potential, in the edge and in the scrape-off layer regions of plasma, with and without the presence of the magnetic field perturbations produced by resonant helical windings. (author). 6 refs., 6 figs

Compact disposal of high-energy electron beams using passive or laser-driven plasma decelerating stage

Energy Technology Data Exchange (ETDEWEB)

Bonatto, A.; Schroeder, C. B.; Vay, J. -L.; Geddes, C. R.; Benedetti, C.; Esarey and, E.; Leemans, W. P.

2014-07-13

A plasma decelerating stage is investigated as a compact alternative for the disposal of high-energy beams (beam dumps). This could benefit the design of laser-driven plasma accelerator (LPA) applications that require transportability and or high-repetition-rate operation regimes. Passive and laser-driven (active) plasma-based beam dumps are studied analytically and with particle-in-cell (PIC) simulations in a 1D geometry. Analytical estimates for the beam energy loss are compared to and extended by the PIC simulations, showing that with the proposed schemes a beam can be efficiently decelerated in a centimeter-scale distance.

Discussion of "Fluvial system response to late Pleistocene-Holocene sea-level change on Santa Rosa Island, Channel Islands National Park, California" (Schumann et al., 2016. Geomorphology, 268: 322-340)

Science.gov (United States)

Pinter, Nicholas; Hardiman, Mark; Scott, Andrew C.; Anderson, R. Scott

2018-01-01

Schumann et al. (2016) presented a field assessment of late Pleistocene to Holocene fluvial sediments preserved in the valleys of Santa Rosa Island, California. This is a rigorous study, based on stratigraphic descriptions of 54 sections and numerous radiocarbon ages. The paper makes important contributions that we would like to highlight, but other parts of the paper rely upon overly simplistic interpretations that lead to misleading conclusions. In one case, a conclusion of the Schumann et al. paper has important management implications for Santa Rosa Island and similar locations, compelling us to discuss and qualify this conclusion.

MTF Driven by Plasma Liner Dynamically Formed by the Merging of Plasma Jets: An Overview

Science.gov (United States)

Thio, Y. C. Francis; Eskridge, Richard; Martin, Adam; Smith, James; Lee, Michael; Rodgers, Stephen L. (Technical Monitor)

2001-01-01

One approach for standoff delivery of the momentum flux for compressing the target in MTF consists of using a spherical array of plasma jets to form a spherical plasma shell imploding towards the center of a magnetized plasma, a compact toroid (Figure 1). A 3-year experiment (PLX-1) to explore the physics of forming a 2-D plasma liner (shell) by merging plasma jets is described. An overview showing how this 3-year project (PLX-1) fits into the program plan at the national and international level for realizing MTF for energy and propulsion is discussed. Assuming that there will be a parallel program in demonstrating and establishing the underlying physics principles of MTF using whatever liner is appropriate (e.g. a solid liner) with a goal of demonstrating breakeven by 2010, the current research effort at NASA MSFC attempts to complement such a program by addressing the issues of practical embodiment of MTF for propulsion. Successful conclusion of PLX-1 will be followed by a Physics Feasibility Experiment (PLX-2) for the Plasma Liner Driven MTF.

Resonant absorption of radar waves by a magnetized collisional plasma

International Nuclear Information System (INIS)

Sun Aiping; Tong Honghui; Shen Liru; Tang Deli; Qiu Xiaoming

2001-01-01

The propagation of radar waves in a magnetized collisional plasma slab is studied numerically. It is found for uniform plasma that: first, the wave attenuation and absorbed power show a peak value, i.e., resonant absorption when the collision frequency f en = 0.1, 0.5, 1 GHz and the wave frequency nears upper hybrid frequency. Secondly, the attenuation, absorbed, and transmitted power curves become flat at f en = 5, 10 Ghz. thirdly, the attenuation and absorbed power increase with plasma density, and the attenuation and the proportion of absorbed power can reach 100 dB and 80%, respectively, at the plasma density n = 10 11 cm -3 . For nonuniform plasma, the peak value of reflected power is larger than that in uniform plasma. So, uniform magnetized plasma is of more benefit to plasma cloaking

Wake-Field Wave Resonant Excitation in Magnetized Plasmas by Electromagnetic Pulse

International Nuclear Information System (INIS)

Milant'ev, V.P.; Turikov, V.A.

2006-01-01

In this paper the space charge wave excitation process at electromagnetic pulse propagation along external magnetic field in vicinity of electron cyclotron resonance. In hydrodynamic approach it is obtained an equation for plasma density under ponderomotive force action. With help of this equation we investigated a wake-field wave amplitude dependence from resonance detuning. The numerical simulation using a PIC method electromagnetic pulse propagation process in the resonant conditions was done

Plasma diagnostics using laser-excited coupled and transmission ring resonators

International Nuclear Information System (INIS)

Haas, R.A.

1976-01-01

In this paper a simple two-level laser model is used to investigate the frequency response of coupled-cavity laser interferometers. It is found that under certain circumstances, often satisfied by molecular gas lasers, the frequency response exhibits a resonant behavior. This behavior severely complicates the interpretation of coupled-cavity laser interferometer measurements of rapidly varying plasmas. To circumvent this limitation a new type of laser interferometer plasma diagnostic with significantly improved time response was developed. In this interferometer the plasma is located in one arm of a transmission ring resonator cavity that is excited by an externally positioned laser. Thus, the laser is decoupled from the interferometer cavity and the time response of the interferometer is then limited by the Q of the ring resonator cavity. This improved time response is acquired without loss of spatial resolution, but requires a more sensitive signal detector since the laser is no longer used as a detector as it is in conventional coupled-cavity laser interferometers. Thus, the new technique incorporates the speed of the Mach--Zender interferometer and the sensitivity of the coupled-cavity laser interferometer. The basic operating principles of this type of interferometer have been verified using a CO 2 laser

Proton nuclear magnetic resonance spectroscopy of plasma lipoproteins in malignancy

International Nuclear Information System (INIS)

Nabholtz, J.M.; Rossignol, A.; Farnier, M.; Gambert, P.; Tremeaux, J.C.; Friedman, S.; Guerrin, J.

1988-01-01

A recent study described a method of detecting malignant tumors by water-supressed proton nuclear magnetic resonance (1 H NMR) study of plasma. We performed a similar study of the W 1/2, a mean of the full width at half height of the resonances of the methyl and methylene groups of the lipids of plasma lipoproteins which is inversely related to the spin-spin apparent relaxation time (T 2 * ). W 1/2 values were measured at a fixed baseline width of 310 Hz. The study was prospective and blinded and comprised 182 subjects consisting of 40 controls, 68 patients with untreated malignancies, 45 with malignant tumors undergoing therapy and 29 benign tumor patients. No differences were seen between any groups that could serve as a basis for a useful clinical test. The major difficulty in the determination of W 1/2 was due to interference of metabolite protons (particularly lactate) within the lipoprotein resonance signal. Triglyceride level was seen to correlate inversely with W 1/2 within malignant patient groups. These discrepant results may be related to differing triglyceride-rich very low density lipoprotein (VLDL) levels in the ;atient populations of each study. We conclude that the water-suppressed 1H NMR of plasma lipoproteins is not a valid measurement for assessing malignancy. (orig.)

Multi-Resonant-Activation for a System Only Driven by Multi-State Noise

International Nuclear Information System (INIS)

Li Jinghui

2010-01-01

We consider the escape of the particles over fluctuating potential barrier for a system only driven by a multi-state noise. It is shown that, the noise can make the particles escape over the fluctuating potential barrier in some circumstances; but in other circumstances, it can not. If the noise can make the particle escape over the fluctuating potential barrier, the mean first passage time (MFPT) can display the phenomenon of multi-resonant-activation. For this phenomenon, there are two kinds of resonant activation to appear. One is resonant activation for the MFPTs as the function of the flipping rates of the fluctuating potential barrier; the other is that for the MFPTs as the functions of the transition rates of the multi-state noise. (general)

Study on low temperature plasma driven permeation of hydrogen

Energy Technology Data Exchange (ETDEWEB)

Takizawa, Masayuki [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

1998-03-01

It is one of the most important problem in PWI of fusion devices from the point of view of tritium leakage that hydrogen diffuses in the wall of the device and permeates through it, which results in hydrogen being released to the coolant side. In this study, plasma driven permeation experiments were carried out with several kinds of metal membranes in the low temperature plasma where ionic and atomic hydrogen as well as electron existed in order to survey PDP mechanism from the many view points. In addition, incident flux rate from the plasma to the membrane surface was evaluated by calculation analysis. As a result the mechanism of low temperature PDP was found out and described as PDP models. The simulation of the membrane pump system was executed and the system performance was estimated with the models. (author). 135 refs.

Study on low temperature plasma driven permeation of hydrogen

International Nuclear Information System (INIS)

Takizawa, Masayuki

1998-03-01

It is one of the most important problem in PWI of fusion devices from the point of view of tritium leakage that hydrogen diffuses in the wall of the device and permeates through it, which results in hydrogen being released to the coolant side. In this study, plasma driven permeation experiments were carried out with several kinds of metal membranes in the low temperature plasma where ionic and atomic hydrogen as well as electron existed in order to survey PDP mechanism from the many view points. In addition, incident flux rate from the plasma to the membrane surface was evaluated by calculation analysis. As a result the mechanism of low temperature PDP was found out and described as PDP models. The simulation of the membrane pump system was executed and the system performance was estimated with the models. (author). 135 refs

Formation of a three-dimensional plasma boundary after decay of the plasma response to resonant magnetic perturbation fields

Science.gov (United States)

Schmitz, O.; Evans, T. E.; Fenstermacher, M. E.; Lanctot, M. J.; Lasnier, C. L.; Mordijck, S.; Moyer, R. A.; Reimerdes, H.; the DIII-D Team

2014-01-01

First time experimental evidence is presented for a direct link between the decay of a n = 3 plasma response and the formation of a three-dimensional (3D) plasma boundary. We inspect a lower single-null L-mode plasma which first reacts at sufficiently high rotation with an ideal resonant screening response to an external toroidal mode number n = 3 resonant magnetic perturbation field. Decay of this response due to reduced bulk plasma rotation changes the plasma state considerably. Signatures such as density pump out and a spin up of the edge rotation—which are usually connected to formation of a stochastic boundary—are detected. Coincident, striation of the divertor single ionized carbon emission and a 3D emission structure in double ionized carbon at the separatrix is seen. The striated C II pattern follows in this stage the perturbed magnetic footprint modelled without a plasma response (vacuum approach). This provides for the first time substantial experimental evidence, that a 3D plasma boundary with direct impact on the divertor particle flux pattern is formed as soon as the internal plasma response decays. The resulting divertor structure follows the vacuum modelled magnetic field topology. However, the inward extension of the perturbed boundary layer can still not directly be determined from these measurements.

Thermoelectric-Driven Liquid-Metal Plasma-Facing Structures (TELS) Final Report

Energy Technology Data Exchange (ETDEWEB)

Ruzic, David [Univ. of Illinois, Urbana-Champaign, IL (United States)

2016-12-17

The Thermoelectric-Driven Liquid-Metal Plasma-Facing Structures (TELS) project was able to establish the experimental conditions necessary for flowing liquid metal surfaces in order to be utilized as surfaces facing fusion relevant energetic plasma flux. The work has also addressed additional developments along with progressing along the timeline detailed in the proposal. A no-cost extension was requested to conduct other relevant experiment- specifically regarding the characterization droplet ejection during energetic plasma flux impact. A specially designed trench module, which could accommodate trenches with different aspect ratios was fabricated and installed in the TELS setup and plasma gun experiments were performed. Droplet ejection was characterized using high speed image acquisition and also surface mounted probes were used to characterize the plasma. The Gantt chart below had been provided with the original proposal, indicating the tasks to be performed in the third year of funding. These tasks are listed above in the progress report outline, and their progress status is detailed below.

Wireless transmission of power

International Nuclear Information System (INIS)

Grotz, T.

1991-01-01

This paper reports that it has been proven by researchers that electrical energy can be propagated around the world between the surface of the Earth and the ionosphere at extremely low frequencies in what is known as the Schumann Cavity. Experiments to data have shown that electromagnetic waves with frequencies in the range of 8 Hz, the fundamental Schumann Resonance frequency, propagate with litter attenuation around the planet within the Schumann Cavity. It is the intent of this research to determine if the Schumann Cavity can be resonated, if the power that is delivered to the cavity propagated with very low losses, and if power can be extracted at other locations within the cavity. Experimental data collected and calculations made in recent years support the hypothesis that wireless power transmission is a viable and practical alternative to the present systems of power transmission

Visualization and simulation of density driven convection in porous media using magnetic resonance imaging

Science.gov (United States)

Montague, James A.; Pinder, George F.; Gonyea, Jay V.; Hipko, Scott; Watts, Richard

2018-05-01

Magnetic resonance imaging is used to observe solute transport in a 40 cm long, 26 cm diameter sand column that contained a central core of low permeability silica surrounded by higher permeability well-sorted sand. Low concentrations (2.9 g/L) of Magnevist, a gadolinium based contrast agent, produce density driven convection within the column when it starts in an unstable state. The unstable state, for this experiment, exists when higher density contrast agent is present above the lower density water. We implement a numerical model in OpenFOAM to reproduce the observed fluid flow and transport from a density difference of 0.3%. The experimental results demonstrate the usefulness of magnetic resonance imaging in observing three-dimensional gravity-driven convective-dispersive transport behaviors in medium scale experiments.

Properties of the electrostatically driven helical plasma state

Science.gov (United States)

Akçay, Cihan; Finn, John M.; Nebel, Richard A.; Barnes, Daniel C.; Martin, Neal

2018-02-01

A novel plasma state has been found [Akçay et al., Phys. Plasmas 24, 052503 (2017)] in the presence of a uniform applied axial magnetic field in periodic cylindrical geometry. This state is driven by external electrostatic fields provided by helical electrodes with a (m =1 ,n =1 ) (helical) symmetry where m and n represent the poloidal and axial harmonics. The resulting plasma is a function of the cylinder radius r safety factor q0(r ) just above the pitch of the electrodes m /n =1 in the interior, where the plasma is nearly force-free. However, at the edge the current density has a component perpendicular to the magnetic field B. This perpendicular current density drives nearly Alfvénic helical plasma flows, a notable feature of these states. This state is being studied for its possible application in DC electrical transformers. We present results on several issues of importance for these applications: the transient leading to the steady state; the twist and writhe of the field lines and their relation with the current density; the properties of the current density streamlines and length of the current density lines connected to the electrodes; the sensitivity to changes in the velocity boundary conditions; the effect of varying the radial resistivity profile; and the effects of a concentrated electrode potential.

An $ep$ collider based on proton-driven plasma wakefield acceleration

CERN Document Server

Wing, M.; Mete, O.; Aimidula, A.; Welsch, C.; Chattopadhyay, S.; Mandry, S.

2014-01-01

Recent simulations have shown that a high-energy proton bunch can excite strong plasma wakefields and accelerate a bunch of electrons to the energy frontier in a single stage of acceleration. This scheme could lead to a future $ep$ collider using the LHC for the proton beam and a compact electron accelerator of length 170 m, producing electrons of energy up to 100 GeV. The parameters of such a collider are discussed as well as conceptual layouts within the CERN accelerator complex. The physics of plasma wakefield acceleration will also be introduced, with the AWAKE experiment, a proof of principle demonstration of proton-driven plasma wakefield acceleration, briefly reviewed, as well as the physics possibilities of such an $ep$ collider.

Enhanced confinement in electron cyclotron resonance ion source plasma.

Science.gov (United States)

Schachter, L; Stiebing, K E; Dobrescu, S

2010-02-01

Power loss by plasma-wall interactions may become a limitation for the performance of ECR and fusion plasma devices. Based on our research to optimize the performance of electron cyclotron resonance ion source (ECRIS) devices by the use of metal-dielectric (MD) structures, the development of the method presented here, allows to significantly improve the confinement of plasma electrons and hence to reduce losses. Dedicated measurements were performed at the Frankfurt 14 GHz ECRIS using argon and helium as working gas and high temperature resistive material for the MD structures. The analyzed charge state distributions and bremsstrahlung radiation spectra (corrected for background) also clearly verify the anticipated increase in the plasma-electron density and hence demonstrate the advantage by the MD-method.

Pulsed radiobiology with laser-driven plasma accelerators

Science.gov (United States)

Giulietti, Antonio; Grazia Andreassi, Maria; Greco, Carlo

2011-05-01

Recently, a high efficiency regime of acceleration in laser plasmas has been discovered, allowing table top equipment to deliver doses of interest for radiotherapy with electron bunches of suitable kinetic energy. In view of an R&D program aimed to the realization of an innovative class of accelerators for medical uses, a radiobiological validation is needed. At the present time, the biological effects of electron bunches from the laser-driven electron accelerator are largely unknown. In radiobiology and radiotherapy, it is known that the early spatial distribution of energy deposition following ionizing radiation interactions with DNA molecule is crucial for the prediction of damages at cellular or tissue levels and during the clinical responses to this irradiation. The purpose of the present study is to evaluate the radio-biological effects obtained with electron bunches from a laser-driven electron accelerator compared with bunches coming from a IORT-dedicated medical Radio-frequency based linac's on human cells by the cytokinesis block micronucleus assay (CBMN). To this purpose a multidisciplinary team including radiotherapists, biologists, medical physicists, laser and plasma physicists is working at CNR Campus and University of Pisa. Dose on samples is delivered alternatively by the "laser-linac" operating at ILIL lab of Istituto Nazionale di Ottica and an RF-linac operating for IORT at Pisa S. Chiara Hospital. Experimental data are analyzed on the basis of suitable radiobiological models as well as with numerical simulation based on Monte Carlo codes. Possible collective effects are also considered in the case of ultrashort, ultradense bunches of ionizing radiation.

Reactive hydroxyl radical-driven oral bacterial inactivation by radio frequency atmospheric plasma

International Nuclear Information System (INIS)

Kang, Sung Kil; Lee, Jae Koo; Choi, Myeong Yeol; Koo, Il Gyo; Kim, Paul Y.; Kim, Yoonsun; Kim, Gon Jun; Collins, George J.; Mohamed, Abdel-Aleam H.

2011-01-01

We demonstrated bacterial (Streptococcus mutans) inactivation by a radio frequency power driven atmospheric pressure plasma torch with H 2 O 2 entrained in the feedstock gas. Optical emission spectroscopy identified substantial excited state OH generation inside the plasma and relative OH formation was verified by optical absorption. The bacterial inactivation rate increased with increasing OH generation and reached a maximum 5-log 10 reduction with 0.6%H 2 O 2 vapor. Generation of large amounts of toxic ozone is drawback of plasma bacterial inactivation, thus it is significant that the ozone concentration falls within recommended safe allowable levels with addition of H 2 O 2 vapor to the plasma.

Summary Report of Working Group 5: Electron Beam Driven Plasma Accelerators

International Nuclear Information System (INIS)

Hogan, Mark J.; Conde, Manoel E.

2009-01-01

Electron beam driven plasma accelerators have seen rapid progress over the last decade. Recent efforts have built on this success by constructing a concept for a plasma wakefield accelerator based linear collider. The needs for any future collider to deliver both energy and luminosity have substantial implications for interpreting current experiments and setting priorities for the future. This working group reviewed current experiments and ideas in the context of the demands of a future collider. The many discussions and presentations are summarized here.

Suppression of large edge localized modes with edge resonant magnetic fields in high confinement DIII-D plasmas

International Nuclear Information System (INIS)

Thomas, P.R.; Becoulet, M.; Evans, T.E.; Osborne, T.H.; Groebner, R.J.; Jackson, G.L.; Haye, R.J. La; Schaffer, M.J.; West, W.P.; Moyer, R.A.; Rhodes, T.L.; Rudakov, D.L.; Watkins, J.G.; Boedo, J.A.; Doyle, E.J.; Wang, G.; Zeng, L.; Fenstermacher, M.E.; Groth, M.; Lasnier, C.J.; Finken, K.H.; Harris, J.H.; Pretty, D.G.; Masuzaki, S.; Ohyabu, N.; Reimerdes, H.; Wade, M.R.

2005-01-01

Large divertor heat pulses due to Type-I edge localized modes (ELMs) have been eliminated reproducibly in DIII-D with small dc currents driven in a simple magnetic perturbation coil. The current required to eliminate all but a few isolated Type-I ELMs, during a coil pulse, is less than 0.4% of plasma current. Modelling shows that the perturbation fields resonate with plasma flux surfaces across most of the pedestal region (0.9 ≤ N ≤ 1.0), when q95 = 3.7±0.2 creating small remnant magnetic islands surrounded by weakly stochastic field lines. The stored energy, N , H-mode quality factor and global energy confinement time are unaltered by the magnetic perturbation. At high collisionality (ν* ∼0.5-1), there is no obvious effect of the perturbation on the edge profiles and yet ELMs are suppressed, nearly completely, for up to 9τ E . At low collisionality (ν* <0.1), there is a density pump-out and complete ELM suppression, reminiscent of the DIIID QH- mode. Other differences, specifically in the resonance condition and the magnetic fluctuations, suggest that different mechanisms are at play in the different collisionality regimes. In addition to a description and interpretation of the DIIID data, the application of this method to ELM control on other machines, such as JET and ITER will be discussed. (author)

Heating of plasmas in tokamaks by current-driven turbulence

International Nuclear Information System (INIS)

Kluiver, H. de.

1985-10-01

Investigations of current-driven turbulence have shown the potential to heat plasmas to elevated temperatures in relatively small cross-section devices. The fundamental processes are rather well understood theoretically. Even as it is shown to be possible to relax the technical requirements on the necessary electric field and the pulse length to acceptable values, the effect of energy generation near the plasma edge, the energy transport, the impurity influx and the variation of the current profile are still unknown for present-day large-radius tokamaks. Heating of plasmas by quasi-stationary weakly turbulent states caused by moderate increases of the resistivity due to higher loop voltages could be envisaged. Power supplies able to furnish power levels 5-10 times higher than the usual values could be used for a demonstration of those regimes. At several institutes and university laboratories the study of turbulent heating in larger tokamaks and stellarators is pursued

Summary report : working group 5 on 'electron beam-driven plasma and structure based acceleration concepts'

International Nuclear Information System (INIS)

Conde, M. E.; Katsouleas, T.

2000-01-01

The talks presented and the work performed on electron beam-driven accelerators in plasmas and structures are summarized. Highlights of the working group include new experimental results from the E-157 Plasma Wakefield Experiment, the E-150 Plasma Lens Experiment and the Argonne Dielectric Structure Wakefield experiments. The presentations inspired discussion and analysis of three working topics: electron hose instability, ion channel lasers and the plasma afterburner

Plasma turbulence driven by transversely large-scale standing shear Alfvén waves

International Nuclear Information System (INIS)

Singh, Nagendra; Rao, Sathyanarayan

2012-01-01

Using two-dimensional particle-in-cell simulations, we study generation of turbulence consisting of transversely small-scale dispersive Alfvén and electrostatic waves when plasma is driven by a large-scale standing shear Alfvén wave (LS-SAW). The standing wave is set up by reflecting a propagating LS-SAW. The ponderomotive force of the standing wave generates transversely large-scale density modifications consisting of density cavities and enhancements. The drifts of the charged particles driven by the ponderomotive force and those directly caused by the fields of the standing LS-SAW generate non-thermal features in the plasma. Parametric instabilities driven by the inherent plasma nonlinearities associated with the LS-SAW in combination with the non-thermal features generate small-scale electromagnetic and electrostatic waves, yielding a broad frequency spectrum ranging from below the source frequency of the LS-SAW to ion cyclotron and lower hybrid frequencies and beyond. The power spectrum of the turbulence has peaks at distinct perpendicular wave numbers (k ⊥ ) lying in the range d e −1 -6d e −1 , d e being the electron inertial length, suggesting non-local parametric decay from small to large k ⊥ . The turbulence spectrum encompassing both electromagnetic and electrostatic fluctuations is also broadband in parallel wave number (k || ). In a standing-wave supported density cavity, the ratio of the perpendicular electric to magnetic field amplitude is R(k ⊥ ) = |E ⊥ (k ⊥ )/|B ⊥ (k ⊥ )| ≪ V A for k ⊥ d e A is the Alfvén velocity. The characteristic features of the broadband plasma turbulence are compared with those available from satellite observations in space plasmas.

Confluence or independence of microwave plasma bullets in atmospheric argon plasma jet plumes

Science.gov (United States)

Li, Ping; Chen, Zhaoquan; Mu, Haibao; Xu, Guimin; Yao, Congwei; Sun, Anbang; Zhou, Yuming; Zhang, Guanjun

2018-03-01

Plasma bullet is the formation and propagation of a guided ionization wave (streamer), normally generated in atmospheric pressure plasma jet (APPJ). In most cases, only an ionization front produces in a dielectric tube. The present study shows that two or three ionization fronts can be generated in a single quartz tube by using a microwave coaxial resonator. The argon APPJ plumes with a maximum length of 170 mm can be driven by continuous microwaves or microwave pulses. When the input power is higher than 90 W, two or three ionization fronts propagate independently at first; thereafter, they confluence to form a central plasma jet plume. On the other hand, the plasma bullets move independently as the lower input power is applied. For pulsed microwave discharges, the discharge images captured by a fast camera show the ionization process in detail. Another interesting finding is that the strongest lightening plasma jet plumes always appear at the shrinking phase. Both the discharge images and electromagnetic simulations suggest that the confluence or independent propagation of plasma bullets is resonantly excited by the local enhanced electric fields, in terms of wave modes of traveling surface plasmon polaritons.

Modeling of Perpendicularly Driven Dual-Frequency Capacitively Coupled Plasma

International Nuclear Information System (INIS)

Wang Hongyu; Sun Peng; Zhao Shuangyun; Li Yang; Jiang Wei

2016-01-01

We analyzed perpendicularly configured dual-frequency (DF) capacitively coupled plasmas (CCP). In this configuration, two pairs of electrodes are arranged oppositely, and the discharging is perpendicularly driven by two radio frequency (RF) sources. Particle-in-cell/Monte Carlo (PIC/MC) simulation showed that the configuration had some advantages as this configuration eliminated some dual frequency coupling effects. Some variation and potential application of the discharging configuration is discussed briefly. (paper)

The role of current sheet formation in driven plasmoid reconnection in laser-produced plasma bubbles

Science.gov (United States)

Lezhnin, Kirill; Fox, William; Bhattacharjee, Amitava

2017-10-01

We conduct a multiparametric study of driven magnetic reconnection relevant to recent experiments on colliding magnetized laser produced plasmas using the PIC code PSC. Varying the background plasma density, plasma resistivity, and plasma bubble geometry, the results demonstrate a variety of reconnection behavior and show the coupling between magnetic reconnection and global fluid evolution of the system. We consider both collision of two radially expanding bubbles where reconnection is driven through an X-point, and collision of two parallel fields where reconnection must be initiated by the tearing instability. Under various conditions, we observe transitions between fast, collisionless reconnection to a Sweet-Parker-like slow reconnection to complete stalling of the reconnection. By varying plasma resistivity, we observe the transition between fast and slow reconnection at Lundquist number S 103 . The transition from plasmoid reconnection to a single X-point reconnection also happens around S 103 . We find that the criterion δ /di < 1 is necessary for fast reconnection onset. Finally, at sufficiently high background density, magnetic reconnection can be suppressed, leading to bouncing motion of the magnetized plasma bubbles.

High explosive driven plasma opening switches

International Nuclear Information System (INIS)

Greene, A.E.; Bowers, R.L.; Brownell, J.H.; Goforth, J.H.; Oliphant, T.A.; Weiss, D.L.

1983-01-01

A joint theoretical and experimental effort is underway to understand and improve upon the performance of high explosive driven plasma opening switches such as those first described by Pavlovskii et al. We have modeled these switches in both planar and cylindrical geometry using a one dimensional Lagrangian MHD code. This one-dimensional analysis is now essentially complete. It has shown that simple, one-dimensional, compression of the current-carrying channel can explain the observed resistance increases during the time of flight of the HE detonation products. Our calculations imply that ionization plays an important role as an energy sink and the performance of these switches might be improved by a judicious choice of gases. We also predict improved performance by lowering the pressure in the plasma channel. The bulk of our experimental effort to date has been with planar switches. We have worked with current densities of 0.25 to 0.4 MA/cm and have observed resistance increases of 40 to 60 mΩ. Significant resistance increases are observed later than the time of flight of the HE detonation products. We suggest that these resistance increases are due to mixing between the hot plasma and the relatively cooler detonation products. Such mixing is not included in the 1-D, Lagrangian code. We are presently beginning a computational effort with a 2-D Eulerian code. The status of this effort is discussed. Experimentally we have designed an apparatus that will permit us to test the role of different gases and pressures. This system is also in a planar geometry, but the plasma channel is doughnut shaped, permitting us to avoid edge effects associated with the planar rectangular geometry. The first experiments with this design are quite encouraging and the status of this effort is also discussed

Mode converter for electron cyclotron resonance heating of toroidal plasmas

International Nuclear Information System (INIS)

Motley, R.W.; Hsuan, H.; Glanz, J.

1980-09-01

A method is proposed for improving the efficiency of cyclotron resonance heating of a toroidal plasma by ordinary mode radiation from the outside of the torus. Radiation not absorbed in the first pass is reflected from the inside of the torus by a corrugated surface which rotates the polarization by 90 0 , so that a secondary source of extraordinary waves is created in the high field, accessible region of the plasma

Magneto-acoustic resonance in a non-uniform current carrying plasma column

OpenAIRE

Vaclavik, J.

2017-01-01

The forced radial magneto-acoustic oscillations in a plasma column with nonuniform mass density and temperature are investigated. It turns out that the oscillations have a resonant character similar to that of the magneto-acoustic oscillations in a uniform plasma column. The properties of the axial and azimuthal components of the oscillating magnetic field are discussed in detail

Laterally Driven Resonant Pressure Sensor with Etched Silicon Dual Diaphragms and Combined Beams

Directory of Open Access Journals (Sweden)

Xiaohui Du

2016-01-01

Full Text Available A novel structure of the resonant pressure sensor is presented in this paper, which tactfully employs intercoupling between dual pressure-sensing diaphragms and a laterally driven resonant strain gauge. After the resonant pressure sensor principle is introduced, the coupling mechanism of the diaphragms and resonator is analyzed and the frequency equation of the resonator based on the triangle geometry theory is developed for this new coupling structure. The finite element (FE simulation results match the theoretical analysis over the full scale of the device. This pressure sensor was first fabricated by dry/wet etching and thermal silicon bonding, followed by vacuum-packaging using anodic bonding technology. The test maximum error of the fabricated sensor is 0.0310%F.S. (full scale in the range of 30 to 190 kPa, its pressure sensitivity is negative and exceeding 8 Hz/kPa, and its Q-factor reaches 20,000 after wafer vacuum-packaging. A novel resonant pressure sensor with high accuracy is presented in this paper.

Resonant activation in 2D and 3D systems driven by multi-variate Lévy noise

International Nuclear Information System (INIS)

Szczepaniec, Krzysztof; Dybiec, Bartłomiej

2014-01-01

Resonant activation is one of the classical effects demonstrating the constructive role of noise. In resonant activation, the cooperative action of a barrier modulation process and noise lead to the optimal escape kinetics as measured by the mean first passage time. Resonant activation has been observed in versatile systems for various types of barrier modulation process and noise type. Here, we show that resonant activation is also observed in 2D and 3D systems driven by bi-variate and tri-variate α-stable noise. The strength of resonant activation is sensitive to the exact value of the noise parameters. In particular, the decrease in the stability index α results in the disappearance of the resonant activation. (paper)

Geometric scalings for the electrostatically driven helical plasma state

Science.gov (United States)

Akçay, Cihan; Finn, John M.; Nebel, Richard A.; Barnes, Daniel C.

2017-12-01

A new plasma state has been investigated [Akcay et al., Phys. Plasmas 24, 052503 (2017)], with a uniform applied axial magnetic field in a periodic cylinder of length L = 2 π R , driven by helical electrodes. The drive is single helicity, depending on m θ + k z = m θ - n ζ , where ζ = z / R and k = - n / R . For strong ( m , n ) = ( 1 , 1 ) drive, the state was found to have a strong axial mean current density, with a mean-field safety factor q 0 ( r ) just above the pitch of the electrodes m / n = 1 in the interior. This state has possible applications to DC electrical transformers and tailoring of the current profile in tokamaks. We study two geometric issues of interest for these applications: (i) scaling of properties with the plasma length or aspect ratio and (ii) behavior for different helicities, specifically ( m , n ) = ( 1 , n ) for n > 1 and ( m , n ) = ( 2 , 1 ) .

Dynamics of plasma ions motion in ultra-intense laser-excited plasma wakes

International Nuclear Information System (INIS)

Zhou Suyun; Li Jing

2013-01-01

The effects of heavy ions and protons motion in an ultra-intense laser-driven plasma wake are compared by rebuilding a plasma wake model. It is shown that with the same laser and plasma background electron density n 0 , the heavy ions' motion suppresses wake-field resonant excitation less than the protons' motion in their own plasma wake. Though heavy ions obtain more kinetic energy from the plasma wake, its energy density is less than that of the protons due to the ion density being far less than the proton density. As a result, the total energy of heavy ions obtained from the wake-field is far less than that of protons. The dependence of the kinetic energy and the energy density of protons and heavy ions on n 0 is discussed. (paper)

Formation of thermal eddies during rf heating of plasma

International Nuclear Information System (INIS)

Motley, R.W.; Hooke, W.M.; Anania, G.

1979-07-01

Moderate power (approx.1 kW) excitation of lower hybrid waves in a linear plasma column is found to increase the reflectivity of the phased waveguide exciter and to change the vertical position of the resonance cone. Probing of the plasma near the mouth of the waveguide reveals that the increased reflection results from an undulation in the plasma surface. We present evidence that this surface distortion is driven by thermal eddies associated with asymmetrical electron heating

Electron temperature gradient driven instability in the tokamak boundary plasma

International Nuclear Information System (INIS)

Xu, X.Q.; Rosenbluth, M.N.; Diamond, P.H.

1992-01-01

A general method is developed for calculating boundary plasma fluctuations across a magnetic separatrix in a tokamak with a divertor or a limiter. The slab model, which assumes a periodic plasma in the edge reaching the divertor or limiter plate in the scrape-off layer(SOL), should provide a good estimate, if the radial extent of the fluctuation quantities across the separatrix to the edge is small compared to that given by finite particle banana orbit. The Laplace transform is used for solving the initial value problem. The electron temperature gradient(ETG) driven instability is found to grow like t -1/2 e γmt

Dynamics of a multiple-pulse-driven x-ray laser plasma

International Nuclear Information System (INIS)

Wan, A.S.; Da Silva, L.B.; Moreno, J.C.; Cauble, R.; Celliers, P.; Dalhed, H.E. Jr.; Koch, J.A.; Nilsen, J.

1996-01-01

In this paper we describe experimental and computational studies of multiple-pulse-driven laser plasma, which is the gain medium for a neon-like yttrium x-ray laser. Near-field emission profiles have been measured both with and without reinjection of the x-ray laser photons to couple with the amplifying medium created by later pulses using an external multilayer mirror. From the temporal and spatial evolution of the near-field emission profiles we can examine the pulse-to-pulse variation of the x-ray laser plasma due to changes in the hydrodynamics, laser deposition, and the injecting of x-ray laser photons back into an amplifying x-ray laser plasma. Using a combination of radiation hydrodynamics, atomic kinetics, and ray propagation codes, reasonable agreement has been obtained between simulations and the experimental results. copyright 1996 American Institute of Physics

Phase locking and quantum statistics in a parametrically driven nonlinear resonator

OpenAIRE

Hovsepyan, G. H.; Shahinyan, A. R.; Chew, Lock Yue; Kryuchkyan, G. Yu.

2016-01-01

We discuss phase-locking phenomena at low-level of quanta for parametrically driven nonlinear Kerr resonator (PDNR) in strong quantum regime. Oscillatory mode of PDNR is created in the process of a degenerate down-conversion of photons under interaction with a train of external Gaussian pulses. We calculate the Wigner functions of cavity mode showing two-fold symmetry in phase space and analyse formation of phase-locked states in the regular as well as the quantum chaotic regime.

Doubly excited 2s2p 1,3Po resonance states of helium in dense plasmas

International Nuclear Information System (INIS)

Kar, Sabyasachi; Ho, Y.K.

2005-01-01

We have made an investigation on the 2s2p 1,3 P o resonance states of helium embedded in dense plasma environments. A screened Coulomb potential obtained from the Debye model is used to represent the interaction between the charge particles. A correlated wave function consisting of a generalized exponential expansion has been used to represent the correlation effect. Resonance energies and widths for the doubly excited He embedded in plasmas with various Debye lengths are determined using the stabilization method by calculating the density of resonance states. The resonance energies and widths for various Debye parameters ranging from infinity to a small value for the lowest 1,3 P o resonance states are reported

Maintenance of the resonance in a cavity filled with a variable density plasma; Entretien de la resonance d'une cavite chargee par un plasma de densite variable

Energy Technology Data Exchange (ETDEWEB)

Melin, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1969-07-01

A study has been made of the possibility of keeping in resonance a cavity filled with a plasma of variable density; only the low HF power zone has been examined (less than a few dozen W). A calculation is first made, for the chosen experimental conditions, of the slipping of the resonance frequency of a cavity as a function of the plasma parameters (density, temperature), with a view to obtaining an idea of its importance. A description is then given of the experimental set-up: the S band cavity (3000 Mc/sec) is supplied by a carcinotron type generator; use is made of the plasma of a positive column whose density ({approx}10{sup 11} cm{sup -3}) can easily be controlled so as to obtain slipping of the cavity frequency ({delta}F{sub max} {approx} 50 Mc/s). The zone of automatic agreement thus obtained for the S band is 3 per cent continuously ({approx}100 Mc/s) and 1 per cent ({approx}30 Mc/s) with a response time of 10 {mu}s (sudden changes in density, {delta}n {approx} 5.10{sup 10} cm{sup 3}). These characteristics already compare very favorably with existing systems, and can easily be improved. (author) [French] On etudie une possibilite de maintenir a la resonance une cavite chargee par un plasma dont la densite varie; on se limite au domaine des puissances HF faibles (< quelques dizaines de W). On calcule tout d'abord, pour les conditions experimentales choisies, le glissement de la frequence de resonance d'une cavite en fonction des parametres du plasma, densite, temperature, pour en evaluer les ordres de grandeur. On decrit ensuite la realisation experimentale: la cavite bande S (3000 Mc/s) est alimentee par un generateur du type carcinotron; on utilise le plasma d'une colonne positive, dont on controle facilement la densite ({approx}10{sup 11} cm{sup -3}) pour faire glisser en frequence la cavite ({delta}F{sub max} {approx} 50 Mc/s). La zone d'accord automatique obtenue ainsi pour la bande S est de 3 pour cent en continu ({approx}100 Mc/s), de 1 pour cent

Time-resolved resonance fluorescence spectroscopy for study of chemical reactions in laser-induced plasmas.

Science.gov (United States)

Liu, Lei; Deng, Leimin; Fan, Lisha; Huang, Xi; Lu, Yao; Shen, Xiaokang; Jiang, Lan; Silvain, Jean-François; Lu, Yongfeng

2017-10-30

Identification of chemical intermediates and study of chemical reaction pathways and mechanisms in laser-induced plasmas are important for laser-ablated applications. Laser-induced breakdown spectroscopy (LIBS), as a promising spectroscopic technique, is efficient for elemental analyses but can only provide limited information about chemical products in laser-induced plasmas. In this work, time-resolved resonance fluorescence spectroscopy was studied as a promising tool for the study of chemical reactions in laser-induced plasmas. Resonance fluorescence excitation of diatomic aluminum monoxide (AlO) and triatomic dialuminum monoxide (Al 2 O) was used to identify these chemical intermediates. Time-resolved fluorescence spectra of AlO and Al 2 O were used to observe the temporal evolution in laser-induced Al plasmas and to study their formation in the Al-O 2 chemistry in air.

Magnetic Field Dependence and Q of the Josephson Plasma Resonance

DEFF Research Database (Denmark)

Pedersen, Niels Falsig; Finnegan, T. F.; Langenberg, D. N.

1972-01-01

of supercurrent density which is not observed in conventional measurements of the field-dependent critical current. The frequency and field dependence of the plasma-resonance linewidth are interpreted as evidence that the previously unobserved quasiparticle-pair-interference tunnel current predicted by Josephson...

Non-diffusive transport in 3-D pressure driven plasma turbulence

International Nuclear Information System (INIS)

Del-Castillo-Negrete, D.; Carreras, B.A.; Lynch, V.

2005-01-01

Numerical evidence of non-diffusive transport in 3-dimensional, resistive, pressure-gradient-driven plasma turbulence is presented. It is shown that the probability density function (pdf) of tracers is strongly non-Gaussian and exhibits algebraic decaying tails. To describe these results, a transport model using fractional derivative operators in proposed. The model incorporates in a unified way non-locality (i.e., non-Fickian transport), memory effects (i.e., non-Markovian transport), and non-diffusive scaling features known to be present in fusion plasmas. There is quantitative agreement between the model and the turbulent transport numerical calculations. In particular, the model reproduces the shape and space-time scaling of the pdf, and the super-diffusive scaling of the moments. (author)

On the gyro resonance electron-whistler interaction in transition layers of near-earth plasma

International Nuclear Information System (INIS)

Erokhin, N.S.; Zol'nikova, N.N.; Mikhajlovskaya, L.A.

1996-01-01

Gyro resonance interaction of electrons with low amplitude triggered whistler in the transition layers of the ionospheric and magnetospheric plasma that correspond to the blurred jumps of the magnetic field and plasma concentration was studied

Excitation and absorption of electromagnetic waves in helicon discharges by plasma immersed antennas

International Nuclear Information System (INIS)

Cho, S.

1998-01-01

Excitation and absorption of electromagnetic waves are numerically studied for helicon discharges driven by antennas immersed in the plasma. The Maxwell equations are reduced to a set of ordinary differential equations, which are solved for radially inhomogeneous plasmas by using the shooting method. Numerical results show that the plasma resistance is much larger and its peaks due to eigenmode resonance appear at higher densities for the immersed antenna case than for the case of the antenna located outside the plasma under otherwise same conditions. It is also found that the m=-1 mode can be excited in the nonuniform plasma with an inner antenna, while it can be hardly excited when the plasma is driven by an outer antenna. In addition, the fast wave approximation neglecting the electron inertia is discussed. (author)

Computer simulation of a plasma focus device driven by a magnetic pulser

Energy Technology Data Exchange (ETDEWEB)

Georgescu, N; Zoita, V [Inst. of Physics and Technology of Radiation Devices, Bucharest (Romania); Larour, J [Ecole Polytechnique, Palaiseau (France). Lab. de Physique des Milieux Ionises

1997-12-31

A plasma focus device, driven by a magnetic pulse compression circuit, is simulated by using a PSPICE proffam. The elaborated program is much simpler than the other existing ones, which analyse the circuit by directly solving a system of integral-differential equations. The pre-pulse voltage and the high-voltage rise-times are obtained for a set of values of the bypass impedance (R or L). The optimum bypass impedance turns out to be an inductance. During the discharge period, the plasma load is considered as an LR impedance, each component being time dependent. A method is presented for giving us the possibility to introduce the time varying impedances in a PSPICE program. Finally, a set of simulation results (plasma current and voltage, plasma magnetic energy, plasma sheath mechanical energy, pinch voltage) is shown. The results are in good agreement with the classical experimental data. (author). 2 figs., 4 refs.

Suppressing magnetic island growth by resonant magnetic perturbation

Science.gov (United States)

Yu, Q.; Günter, S.; Lackner, K.

2018-05-01

The effect of externally applied resonant magnetic perturbations (RMPs) on the growth of magnetic islands is investigated based on two-fluid equations. It is found that if the local bi-normal electron fluid velocity at the resonant surface is sufficiently large, static RMPs of the same helicity and of moderate amplitude can suppress the growth of magnetic islands in high-temperature plasmas. These islands will otherwise grow, driven by an unfavorable plasma current density profile and bootstrap current perturbation. These results indicate that the error field can stabilize island growth, if the error field amplitude is not too large and the local bi-normal electron fluid velocity is not too low. They also indicate that applied rotating RMPs with an appropriate frequency can be utilized to suppress island growth in high-temperature plasmas, even for a low bi-normal electron fluid velocity. A significant change in the local equilibrium plasma current density gradient by small amplitude RMPs is found for realistic plasma parameters, which are important for the island stability and are expected to be more important for fusion reactors with low plasma resistivity.

An Investigation on the He−(1s2s2 2S Resonance in Debye Plasmas

Directory of Open Access Journals (Sweden)

Arijit Ghoshal

2017-01-01

Full Text Available The effect of Debye plasma on the 1 s 2 s 2 2 S resonance states in the scattering of electron from helium atom has been investigated within the framework of the stabilization method. The interactions among the charged particles in Debye plasma have been modelled by Debye–Huckel potential. The 1 s 2 s excited state of the helium atom has been treated as consisting of a H e + ionic core plus an electron moving around. The interaction between the core and the electron has then been modelled by a model potential. It has been found that the background plasma environment significantly affects the resonance states. To the best of our knowledge, such an investigation of 1 s 2 s 2 2 S resonance states of the electron–helium system embedded in Debye plasma environment is the first reported in the literature.

Stochastic resonance in a single-mode laser driven by frequency modulated signal and coloured noises

Institute of Scientific and Technical Information of China (English)

Jin Guo-Xiang; Zhang Liang-Ying; Cao Li

2009-01-01

By adding frequency modulated signals to the intensity equation of gain-noise model of the single-mode laser driven by two coloured noises which are correlated, this paper uses the linear approximation method to calculate the power spectrum and signal-to-noise ratio (SNR) of the laser intensity. The results show that the SNR appears typical stochastic resonance with the variation of intensity of the pump noise and quantum noise. As the amplitude of a modulated signal has effects on the SNR, it shows suppression, monotone increasing, stochastic resonance, and multiple stochastic resonance with the variation of the frequency of a carrier signal and modulated signal.

Semi-analytical model of laser resonance absorption in plasmas with a parabolic density profile

International Nuclear Information System (INIS)

Pestehe, S J; Mohammadnejad, M

2010-01-01

Analytical expressions for mode conversion and resonance absorption of electromagnetic waves in inhomogeneous, unmagnetized plasmas are required for laboratory and simulation studies. Although most of the analyses of this problem have concentrated on the linear plasma density profile, there are a few research works that deal with different plasma density profiles including the parabolic profile. Almost none of them could give clear analytical formulae for the electric and magnetic components of the electromagnetic field propagating through inhomogeneous plasmas. In this paper, we have considered the resonant absorption of laser light near the critical density of plasmas with parabolic electron density profiles followed by a uniform over-dense region and have obtained expressions for the electric and magnetic vectors of laser light propagating through the plasma. An estimation of the fractional absorption of laser energy has also been carried out. It has been shown that, in contrast to the linear density profile, the energy absorption depends explicitly on the value of collision frequency as well as on a new parameter, N, called the over-dense density order.

The Effect of Ion Motion on Laser-Driven Plasma Wake in Capillary

International Nuclear Information System (INIS)

Zhou Suyun; Li Yanfang; Chen Hui

2016-01-01

The effect of ion motion in capillary-guided laser-driven plasma wake is investigated through rebuilding a two-dimensional analytical model. It is shown that laser pulse with the same power can excite more intense wakefield in the capillary of a smaller radius. When laser intensity exceeds a critical value, the effect of ion motion reducing the wakefield rises, which becomes significant with a decrease of capillary radius. This phenomenon can be attributed to plasma ions in smaller capillary obtaining more energy from the plasma wake. The dependence of the difference value between maximal scalar potential of wake for two cases of ion rest and ion motion on the radius of the capillary is discussed. (paper)

Gyrokinetic simulations with external resonant magnetic perturbations: Island torque and nonambipolar transport with plasma rotation

Science.gov (United States)

Waltz, R. E.; Waelbroeck, F. L.

2012-03-01

Static external resonant magnetic field perturbations (RMPs) have been added to the gyrokinetic code GYRO [J. Candy and R. E. Waltz, J. Comp. Phys. 186, 545 (2003)]. This allows nonlinear gyrokinetic simulations of the nonambipolar radial current flow jr, and the corresponding j→×B→ plasma torque (density) R[jrBp/c], induced by magnetic islands that break the toroidal symmetry of a tokamak. This extends the previous GYRO formulation for the transport of toroidal angular momentum (TAM) [R. E. Waltz, G. M. Staebler, J. Candy, and F. L. Hinton, Phys. Plasmas 14, 122507 (2007); errata 16, 079902 (2009)]. The focus is on electrostatic full torus radial slice simulations of externally induced q =m/n=6/3 islands with widths 5% of the minor radius or about 20 ion gyroradii. Up to moderately strong E ×B rotation, the island torque scales with the radial electric field at the resonant surface Er, the island width w, and the intensity I of the high-n micro-turbulence, as Erw√I . The radial current inside the island is carried (entirely in the n =3 component) and almost entirely by the ion E ×B flux, since the electron E ×B and magnetic flutter particle fluxes are cancelled. The net island torque is null at zero Er rather than at zero toroidal rotation. This means that while the expected magnetic braking of the toroidal plasma rotation occurs at strong co- and counter-current rotation, at null toroidal rotation, there is a small co-directed magnetic acceleration up to the small diamagnetic (ion pressure gradient driven) co-rotation corresponding to the zero Er and null torque. This could be called the residual stress from an externally induced island. At zero Er, the only effect is the expected partial flattening of the electron temperature gradient within the island. Finite-beta GYRO simulations demonstrate almost complete RMP field screening and n =3 mode unlocking at strong Er.

Study of the fast electron distribution function in lower hybrid and electron cyclotron current driven plasmas in the WT-3 tokamak

International Nuclear Information System (INIS)

Ogura, K.; Tanaka, H.; Ide, S.

1991-01-01

The distribution function f(p-vector) of fast electrons produced by lower hybrid current drive (LHCD) is investigated in the WT-3 tokamak, using a combination of measurements of the hard X-ray (HXR) angular distribution with respect to the toroidal magnetic field and observations of the HXR radial profile. The data obtained indicate the formation of a plateau-like region in f(p-vector) which corresponds to a region of resonant interaction between the lower hybrid (LH) wave and the electrons. The energy of the fast electrons in the peripheral plasma region is observed to be higher than that in the central plasma region under operational conditions with a high plasma current (I p ≥ 80 kA). At low current (I p < or approx. 50 kA), however, the energy of fast electrons is constant along the plasma radius. In the current ramp-up phase, fast electrons are generated in the directions normal to and opposite to the LH wave propagation. The latter case is ascribed to a negatively biased toroidal electric field induced by the current ramp-up. To study the characteristic change of f(p-vector) for various current drive mechanisms, HXR measurements are performed in electron cyclotron current driven (ECCD) plasma and in Ohmic heating (OH) plasma. In ECCD plasma, the perpendicular energy of fast electrons increases, which indicates that fast electrons are accelerated perpendicularly by electron cyclotron heating. In both LHCD and ECCD plasmas, fast electrons flow in the direction opposite to the wave propagation, while no such fast electrons are formed in OH plasma. (author). 33 refs, 16 figs, 1 tab

Deep-UV high resolution cavity ring-down spectroscopy of the Schumann-Runge bands in O-16(2) and O-18(2) at wavelengths 197-203 nm

NARCIS (Netherlands)

Hannemann, S.; van Duijn, E.J.; Ubachs, W.M.G.

2005-01-01

With the use of a novel titanium:sapphire laser source delivering, upon fourth harmonic generation, narrowband and tunable radiation in the deep-UV, spectroscopic studies were performed on weak Schumann-Runge bands of oxygen. Improved values for rotational and fine structure molecular parameters for

Boltzmann-equation simulations of radio-frequency-driven, low-temperature plasmas

International Nuclear Information System (INIS)

Drallos, P.J.; Riley, M.E.

1995-01-01

We present a method for the numerical solution of the Boltzmann equation (BE) describing plasma electrons. We apply the method to a capacitively-coupled, radio-frequency-driven He discharge in parallel-plate (quasi-1D) geometry which contains time scales for physical processes spanning six orders of magnitude. Our BE solution procedure uses the method of characteristics for the Vlasov operator with interpolation in phase space at early time, allowing storage of the distribution function on a fixed phase-space grid. By alternating this BE method with a fluid description of the electrons, or with a novel time-cycle-average equation method, we compute the periodic steady state of a He plasma by time evolution from startup conditions. We find that the results compare favorably with measured current-voltage, plasma density, and ''cited state densities in the ''GEC'' Reference Cell. Our atomic He model includes five levels (some are summed composites), 15 electronic transitions, radiation trapping, and metastable-metastable collisions

Boltzmann-equation simulations of radio-frequency-driven, low-temperature plasmas

Energy Technology Data Exchange (ETDEWEB)

Drallos, P.J.; Riley, M.E.

1995-01-01

We present a method for the numerical solution of the Boltzmann equation (BE) describing plasma electrons. We apply the method to a capacitively-coupled, radio-frequency-driven He discharge in parallel-plate (quasi-1D) geometry which contains time scales for physical processes spanning six orders of magnitude. Our BE solution procedure uses the method of characteristics for the Vlasov operator with interpolation in phase space at early time, allowing storage of the distribution function on a fixed phase-space grid. By alternating this BE method with a fluid description of the electrons, or with a novel time-cycle-average equation method, we compute the periodic steady state of a He plasma by time evolution from startup conditions. We find that the results compare favorably with measured current-voltage, plasma density, and ``cited state densities in the ``GEC`` Reference Cell. Our atomic He model includes five levels (some are summed composites), 15 electronic transitions, radiation trapping, and metastable-metastable collisions.

Various vibration modes in a silicon ring resonator driven by p–n diode actuators formed in the lateral direction

Science.gov (United States)

Tsushima, Takafumi; Asahi, Yoichi; Tanigawa, Hiroshi; Furutsuka, Takashi; Suzuki, Kenichiro

2018-06-01

In this paper, we describe p–n diode actuators that are formed in the lateral direction on resonators. Because previously reported p–n diode actuators, which were driven by a force parallel to the electrostatic force induced in a p–n diode, were fabricated in the perpendicular direction to the surface, the fabrication process to satisfy the requirement of realizing a p–n junction set in the middle of the plate thickness has been difficult. The resonators in this work are driven by p–n diodes formed in the lateral direction, making the process easy. We have fabricated a silicon ring resonator that has in-plane vibration using p–n–p and n–p–n diode actuators formed in the lateral direction. First, we consider a space charge model that can sufficiently accurately describe the force induced in p–n diode actuators and compare it with the capacitance model used in most computer simulations. Then, we show that multiplying the vibration amplitude calculated by computer simulation by the modification coefficient of 4/3 provides the vibration amplitude in the p–n diode actuators. Good agreement of the theory with experimental results of the in-plane vibration measured for silicon ring resonators is obtained. The computer simulation is very useful for evaluating various vibration modes in resonators driven by the p–n diode actuators. The small amplitude of the p–n diode actuator measured in this work is expected to increase greatly with increased doping of the actuator.

Double plasma resonance instability as a source of solar zebra emission

Science.gov (United States)

Benáček, J.; Karlický, M.

2018-03-01

Context. The double plasma resonance (DPR) instability plays a basic role in the generation of solar radio zebras. In the plasma, consisting of the loss-cone type distribution of hot electrons and much denser and colder background plasma, this instability generates the upper-hybrid waves, which are then transformed into the electromagnetic waves and observed as radio zebras. Aims: In the present paper we numerically study the double plasma resonance instability from the point of view of the zebra interpretation. Methods: We use a 3-dimensional electromagnetic particle-in-cell (3D PIC) relativistic model. We use this model in two versions: (a) a spatially extended "multi-mode" model and (b) a spatially limited "specific-mode" model. While the multi-mode model is used for detailed computations and verifications of the results obtained by the "specific-mode" model, the specific-mode model is used for computations in a broad range of model parameters, which considerably save computational time. For an analysis of the computational results, we developed software tools in Python. Results: First using the multi-mode model, we study details of the double plasma resonance instability. We show how the distribution function of hot electrons changes during this instability. Then we show that there is a very good agreement between results obtained by the multi-mode and specific-mode models, which is caused by a dominance of the wave with the maximal growth rate. Therefore, for computations in a broad range of model parameters, we use the specific-mode model. We compute the maximal growth rates of the double plasma resonance instability with a dependence on the ratio between the upper-hybrid ωUH and electron-cyclotron ωce frequency. We vary temperatures of both the hot and background plasma components and study their effects on the resulting growth rates. The results are compared with the analytical ones. We find a very good agreement between numerical and analytical growth

Plasma heating in multiple-resonance excitation of a plasma in a mirror machine

Energy Technology Data Exchange (ETDEWEB)

Bender, A; Siambis, J G [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA)

1976-06-01

By applying 1 kW of microwave power at 2.45 GHz and 1 kW of r.f. power in the frequency range of 4-25 MHz at one end of a mirror machine, where neutral hydrogen gas is injected in a pulsed mode, a plasma density of 2 x 10/sup 11/cm/sup -3/ with an electron temperature of 60 eV and ion temperature of 40 eV is generated. The ion heating mechanism, is, principally, collisional thermalization of the applied r.f. power, via coupling to and excitation of the low frequency resonances of the plasma column, in agreement with the theoretical prediction for the case of high total effective collision frequency for momentum transfer for the electrons.

Free-electron laser driven by the LBNL laser-plasma accelerator

International Nuclear Information System (INIS)

Schroeder, C.B.; Fawley, W.M.; Gruner, F.; Bakeman, M.; Nakamura, K.; Robinson, K.E.; Toth, Cs.; Esarey, E.; Leemans, W.P.

2008-01-01

A design of a compact free-electron laser (FEL), generating ultra-fast, high-peak flux, XUV pulses is presented. The FEL is driven by ahigh-current, 0.5 GeV electron beam from the Lawrence Berkeley National Laboratory (LBNL) laser-plasma accelerator, whose active acceleration length is only a few centimeters. The proposed ultra-fast source (∼10 fs) would be intrinsically temporally synchronized to the drive laser pulse, enabling pump-probe studies in ultra-fast science. Owing to the high current (>10 kA) of the laser-plasma-accelerated electron beams, saturated output fluxes are potentially greater than 10 13 photons/pulse. Devices based both on self-amplified spontaneous emission and high-harmonic generated input seeds, to reduce undulator length and fluctuations, are considered.

Non-linear magnetohydrodynamic modeling of plasma response to resonant magnetic perturbations

Energy Technology Data Exchange (ETDEWEB)

Orain, F.; Bécoulet, M.; Dif-Pradalier, G.; Nardon, E.; Passeron, C.; Latu, G.; Grandgirard, V.; Fil, A.; Ratnani, A. [CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France); Huijsmans, G. [ITER Organization, Route de Vinon, F-13115 Saint-Paul-Lez-Durance (France); Pamela, S. [IIFS-PIIM. Aix Marseille Université - CNRS, 13397 Marseille Cedex20 (France); Chapman, I.; Kirk, A.; Thornton, A. [EURATOM/CCFE Fusion Association, Culham Science Centre, Oxon OX14 3DB (United Kingdom); Hoelzl, M. [Max-Planck-Institut für Plasmaphysik, EURATOM Association, Garching (Germany); Cahyna, P. [Association EURATOM/IPP.CR, Prague (Czech Republic)

2013-10-15

The interaction of static Resonant Magnetic Perturbations (RMPs) with the plasma flows is modeled in toroidal geometry, using the non-linear resistive MHD code JOREK, which includes the X-point and the scrape-off-layer. Two-fluid diamagnetic effects, the neoclassical poloidal friction and a source of toroidal rotation are introduced in the model to describe realistic plasma flows. RMP penetration is studied taking self-consistently into account the effects of these flows and the radial electric field evolution. JET-like, MAST, and ITER parameters are used in modeling. For JET-like parameters, three regimes of plasma response are found depending on the plasma resistivity and the diamagnetic rotation: at high resistivity and slow rotation, the islands generated by the RMPs at the edge resonant surfaces rotate in the ion diamagnetic direction and their size oscillates. At faster rotation, the generated islands are static and are more screened by the plasma. An intermediate regime with static islands which slightly oscillate is found at lower resistivity. In ITER simulations, the RMPs generate static islands, which forms an ergodic layer at the very edge (ψ≥0.96) characterized by lobe structures near the X-point and results in a small strike point splitting on the divertor targets. In MAST Double Null Divertor geometry, lobes are also found near the X-point and the 3D-deformation of the density and temperature profiles is observed.

Intense laser driven collision-less shock and ion acceleration in magnetized plasmas

Science.gov (United States)

Mima, K.; Jia, Q.; Cai, H. B.; Taguchi, T.; Nagatomo, H.; Sanz, J. R.; Honrubia, J.

2016-05-01

The generation of strong magnetic field with a laser driven coil has been demonstrated by many experiments. It is applicable to the magnetized fast ignition (MFI), the collision-less shock in the astrophysics and the ion shock acceleration. In this paper, the longitudinal magnetic field effect on the shock wave driven by the radiation pressure of an intense short pulse laser is investigated by theory and simulations. The transition of a laminar shock (electro static shock) to the turbulent shock (electromagnetic shock) occurs, when the external magnetic field is applied in near relativistic cut-off density plasmas. This transition leads to the enhancement of conversion of the laser energy into high energy ions. The enhancement of the conversion efficiency is important for the ion driven fast ignition and the laser driven neutron source. It is found that the total number of ions reflected by the shock increases by six time when the magnetic field is applied.

Critical condition for current-driven instability excited in turbulent heating of TRIAM-1 tokamak plasma

Energy Technology Data Exchange (ETDEWEB)

Nakamura, Y; Watanabe, T; Nagao, A; Nakamura, K; Kikuchi, M; Aoki, T; Hiraki, N; Itoh, S [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics; Mitarai, O

1982-02-01

Critical condition for current-driven instability excited in turbulently heated TRIAM-1 tokamak plasma is investigated experimentally. Resistive hump in loop voltage, plasma density fluctuation and rapid increase of electron temperature in a skin layer are simultaneously observed at the time when the electron drift velocity amounts to the critical drift velocity for low-frequency ion acoustic instability.

The permittivity of a plasma at cyclotron resonance in large amplitude e.m. fields

NARCIS (Netherlands)

Schram, D.C.

1970-01-01

The permittivity of a collisionless plasma as a function of field parameters is measured in standing and in travelling waves. In both experiments the permittivity remains finite at cyclotron resonance; the resonance is broadened and shifted towards higher values of the magnetic field strength. The

Basic physics of Alfven instabilities driven by energetic particles in toroidally confined plasmas

International Nuclear Information System (INIS)

Heidbrink, W. W.

2008-01-01

Superthermal energetic particles (EP) often drive shear Alfven waves unstable in magnetically confined plasmas. These instabilities constitute a fascinating nonlinear system where fluid and kinetic nonlinearities can appear on an equal footing. In addition to basic science, Alfven instabilities are of practical importance, as the expulsion of energetic particles can damage the walls of a confinement device. Because of rapid dispersion, shear Alfven waves that are part of the continuous spectrum are rarely destabilized. However, because the index of refraction is periodic in toroidally confined plasmas, gaps appear in the continuous spectrum. At spatial locations where the radial group velocity vanishes, weakly damped discrete modes appear in these gaps. These eigenmodes are of two types. One type is associated with frequency crossings of counterpropagating waves; the toroidal Alfven eigenmode is a prominent example. The second type is associated with an extremum of the continuous spectrum; the reversed shear Alfven eigenmode is an example of this type. In addition to these normal modes of the background plasma, when the energetic particle pressure is very large, energetic particle modes that adopt the frequency of the energetic particle population occur. Alfven instabilities of all three types occur in every toroidal magnetic confinement device with an intense energetic particle population. The energetic particles are most conveniently described by their constants of motion. Resonances occur between the orbital frequencies of the energetic particles and the wave phase velocity. If the wave resonance with the energetic particle population occurs where the gradient with respect to a constant of motion is inverted, the particles transfer energy to the wave, promoting instability. In a tokamak, the spatial gradient drive associated with inversion of the toroidal canonical angular momentum P ζ is most important. Once a mode is driven unstable, a wide variety of

Thermonuclear-driven fast magnetosonic-wave heating in tokamak plasmas

International Nuclear Information System (INIS)

Sutton, W.R. III.

1982-01-01

A thermonuclear driven fast magnetosonic wave instability is investigated in tokamak plasmas for propagation transverse to the external magnetic field at frequencies of several times the alpha particle gyro rate: ω approx. = L Ω/sub α/ = k/sub perpendicular/ v/sub A/, L approx. 4 to 8, k/sub parallel/ << k/sub perpendicular/. The 2-D differential quasi-linear diffusion equation is derived in circular cylindrical, v/sub perpendicular/-v/sub parallel/ geometry. We perform an expansion in the small parameter k/sub parallel/k/sub perpendicucular/ of the quasi-linear diffusion coefficients

Electron cyclotron resonance plasmas and electron cyclotron resonance ion sources: Physics and technology (invited)

International Nuclear Information System (INIS)

Girard, A.; Hitz, D.; Melin, G.; Serebrennikov, K.

2004-01-01

Electron cyclotron resonance (ECR) ion sources are scientific instruments particularly useful for physics: they are extensively used in atomic, nuclear, and high energy physics, for the production of multicharged beams. Moreover, these sources are also of fundamental interest for plasma physics, because of the very particular properties of the ECR plasma. This article describes the state of the art on the physics of the ECR plasma related to multiply charged ion sources. In Sec. I, we describe the general aspects of ECR ion sources. Physics related to the electrons is presented in Sec. II: we discuss there the problems of heating and confinement. In Sec. III, the problem of ion production and confinement is presented. A numerical code is presented, and some particular and important effects, specific to ECR ion sources, are shown in Sec. IV. Eventually, in Sec. V, technological aspects of ECR are presented and different types of sources are shown

Electron plasma waves and plasma resonances

International Nuclear Information System (INIS)

Franklin, R N; Braithwaite, N St J

2009-01-01

In 1929 Tonks and Langmuir predicted of the existence of electron plasma waves in an infinite, uniform plasma. The more realistic laboratory environment of non-uniform and bounded plasmas frustrated early experiments. Meanwhile Landau predicted that electron plasma waves in a uniform collisionless plasma would appear to be damped. Subsequent experimental work verified this and revealed the curious phenomenon of plasma wave echoes. Electron plasma wave theory, extended to finite plasmas, has been confirmed by various experiments. Nonlinear phenomena, such as particle trapping, emerge at large amplitude. The use of electron plasma waves to determine electron density and electron temperature has not proved as convenient as other methods.

Permanent magnet electron cyclotron resonance plasma source with remote window

International Nuclear Information System (INIS)

Berry, L.A.; Gorbatkin, S.M.

1995-01-01

An electron cyclotron resonance (ECR) plasma has been used in conjunction with a solid metal sputter target for Cu deposition over 200 mm diameters. The goal is to develop a deposition system and process suitable for filling submicron, high-aspect ratio ULSI features. The system uses a permanent magnet for creation of the magnetic field necessary for ECR, and is significantly more compact than systems equipped with electromagnets. A custom launcher design allows remote microwave injection with the microwave entrance window shielded from the copper flux. When microwaves are introduced at an angle with respect to the plasma, high electron densities can be produced with a plasma frequency significantly greater than the electron cyclotron frequency. Copper deposition rates of 1000 A/min have been achieved

Stochastic resonance driven by time-modulated correlated coloured noise sources in a single-mode laser

International Nuclear Information System (INIS)

De-Yi, Chen; Li, Zhang

2009-01-01

This paper investigates the phenomenon of stochastic resonance in a single-mode laser driven by time-modulated correlated coloured noise sources. The power spectrum and signal-to-noise ratio R of the laser intensity are calculated by the linear approximation. The effects caused by noise self-correlation time τ 1 , τ 2 and cross-correlated time τ 3 for stochastic resonance are analysed in two ways: τ 1 , τ 2 and τ 3 are taken to be the independent variables and the parameters respectively. The effects of the gain coefficient Γ and loss coefficient K on the stochastic resonance are also discussed. It is found that besides the presence of the standard form and the broad sense of stochastic resonance, the number of extrema in the curve of R versus K is reduced with the increase of the gain coefficient Γ

Plasma Diagnostics in High Density Reactors

International Nuclear Information System (INIS)

Daltrini, A. M.; Moshkalyov, S.; Monteiro, M. J. R.; Machida, M.; Kostryukov, A.; Besseler, E.; Biasotto, C.; Diniz, J. A.

2006-01-01

Langmuir electric probes and optical emission spectroscopy diagnostics were developed for applications in high density plasmas. These diagnostics were employed in two plasma sources: an electron cyclotron resonance (ECR) plasma and an RF driven inductively coupled plasma (ICP) plasma. Langmuir probes were tested using a number of probing dimensions, probe tip materials, circuits for probe bias and filters. Then, the results were compared with the optical spectroscopy measurements. With these diagnostics, analyses of various plasma processes were performed in both reactors. For example, it has been shown that species like NH radicals generated in gas phase can have critical impact on films deposited by ECR plasmas. In the ICP source, plasmas in atomic and molecular gases were shown to have different spatial distributions, likely due to nonlocal electron heating. The low-to-high density transitions in the ICP plasma were also studied. The role of metastables is shown to be significant in Ar plasmas, in contrast to plasmas with additions of molecular gases

Sawtooth events and O+ in the plasma sheet and boundary layer: CME- and SIR-driven events

Science.gov (United States)

Lund, E. J.; Nowrouzi, N.; Kistler, L. M.; Cai, X.; Liao, J.

2017-12-01

The role of ionospheric ions in sawtooth events is an open question. Simulations[1,2,3] suggest that O+ from the ionosphere produces a feedback mechanism for driving sawtooth events. However, observational evidence[4,5] suggest that the presence of O+ in the plasma sheet is neither necessary nor sufficient. In this study we investigate whether the solar wind driver of the geomagnetic storm has an effect on the result. Building on an earlier study[4] that used events for which Cluster data is available in the plasma sheet and boundary layer, we perform a superposed epoch analysis for coronal mass ejection (CME) driven storms and streaming interaction region (SIR) driven storms separately, to investigate the hypothesis that ionospheric O+ is an important contributor for CME-driven storms but not SIR-driven storms[2]. [1]O. J. Brambles et al. (2011), Science 332, 1183.[2]O. J. Brambles et al. (2013), JGR 118, 6026.[3]R. H. Varney et al. (2016), JGR 121, 9688.[4]J. Liao et al. (2014), JGR 119, 1572.[5]E. J. Lund et al. (2017), JGR, submitted.

Analysis of IBW-driven plasma flows in tokamaks

International Nuclear Information System (INIS)

Berry, L.A.; Jaeger, E.F.; D'Azevedo, E.F.; Batchelor, D.B.; Carlsson, J.A.; Carter, M.D.; Cesario, R.

2001-01-01

Both theory and experiment have suggested that damping of Ion Bernstein Waves (IBWs) at ion cyclotron frequency harmonics could drive poloidal flows and lead to enhanced confinement for tokamaks. However, the early analyses were based on Reynolds stress closures of moment equations. More rigorous, finite Larmor radius (FLR) expansions of the radio frequency (RF) kinetic pressure for low harmonic interactions indicated that the Reynolds stress approximation was not generally valid, and resulted in significant changes in the plasma flow response. These changes were largest for wave interactions driven by finite Larmour radius effects. To provide a better assessment of higher harmonic interactions and IBW flow drive prospects, the electromagnetic (E and M) and RF kinetic force models are extended with no assumptions regarding the smallness of the ion Larmor radius. For both models, a spectral-width approximation was used to make the numerical analysis tractable. In addition, it was necessary to include the effects of plasma equilibrium gradients on the plasma conductivity and the RF-induced momentum in order to conserve energy and momentum. The analysis of high-harmonic IBW interactions for TFTR and FTU parameters indicates significant poloidal flow shears (relative to turbulence correlation times) for power levels available in present experiments. Recent advances in all-orders calculations of E and M fields in 2-D are also discussed. (author)

Three-dimensional FDTD Modeling of Earth-ionosphere Cavity Resonances

Science.gov (United States)

Yang, H.; Pasko, V. P.

2003-12-01

Resonance properties of the earth-ionosphere cavity were first predicted by W. O. Schumann in 1952 [Schumann, Z. Naturforsch. A, 7, 149, 1952]. Since then observations of extremely low frequency (ELF) signals in the frequency range 1-500 Hz have become a powerful tool for monitoring of global lightning activity and planetary scale variability of the lower ionosphere, as well as, in recent years, for location and remote sensing of sprites, jets and elves and associated lightning discharges [e.g., Sato et al., JASTP, 65, 607, 2003; Su et al., Nature, 423, 974, 2003; and references cited therein]. The simplicity and flexibility of finite difference time domain (FDTD) technique for finding first principles solutions of electromagnetic problems in a medium with arbitrary inhomogeneities and ever-increasing computer power make FDTD an excellent candidate to be the technique of the future in development of realistic numerical models of VLF/ELF propagation in Earth-ionosphere waveguide [Cummer, IEEE Trans. Antennas Propagat., 48, 1420, 2000], and several reports about successful application of the FDTD technique for solution of related problems have recently appeared in the literature [e.g., Thevenot et al., Ann. Telecommun., 54, 297, 1999; Cummer, 2000; Berenger, Ann. Telecommun., 57, 1059, 2002, Simpson and Taflove, IEEE Antennas Wireless Propagat. Lett., 1, 53, 2002]. In this talk we will present results from a new three-dimensional spherical FDTD model, which is designed for studies of ELF electromagnetic signals under 100 Hz in the earth-ionosphere cavity. The model accounts for a realistic latitudinal and longitudinal variation of ground conductivity (i.e., for the boundaries between oceans and continents) by employing a broadband surface impedance technique proposed in [Breggs et al., IEEE Trans. Antenna Propagat., 41, 118, 1993]. The realistic distributions of atmospheric/lower ionospheric conductivity are derived from the international reference ionosphere model

Theoretical investigation of resonance frequencies in long wavelength electromagnetic wave scattering process from plasma prolate and oblate spheroids placed in a dielectric layer

Science.gov (United States)

Ahmadizadeh, Y.; Jazi, B.; Abdoli-Arani, A.

2014-01-01

Response of a prolate spheroid plasma and/or an oblate spheroid plasma in presence of long wavelength electromagnetic wave has been studied. The resonance frequencies of these objects are obtained and it is found that they reduce to the resonance frequency of spherical cold plasma. Moreover, the resonant frequencies of prolate spheroid plasma and oblate spheroid plasma covered by a dielectric are investigated as well. Furthermore, their dependency on dielectric permittivity and geometry dimensions is simulated.

Stochastic resonance in multi-stable coupled systems driven by two driving signals

Science.gov (United States)

Xu, Pengfei; Jin, Yanfei

2018-02-01

The stochastic resonance (SR) in multi-stable coupled systems subjected to Gaussian white noises and two different driving signals is investigated in this paper. Using the adiabatic approximation and the perturbation method, the coupled systems with four-well potential are transformed into the master equations and the amplitude of the response is obtained. The signal-to-noise ratio (SNR) is calculated numerically to demonstrate the occurrence of SR. For the case of two driving signals with different amplitudes, the interwell resonance between two wells S1 and S3 emerges for strong coupling. The SR can appear in the subsystem with weaker signal amplitude or even without driving signal with the help of coupling. For the case of two driving signals with different frequencies, the effects of SR in two subsystems driven by high and low frequency signals are both weakened with an increase in coupling strength. The stochastic multi-resonance phenomenon is observed in the subsystem subjected to the low frequency signal. Moreover, an effective scheme for phase suppressing SR is proposed by using a relative phase between two driving signals.

A compact and continuously driven supersonic plasma and neutral source

Energy Technology Data Exchange (ETDEWEB)

Asai, T.; Itagaki, H.; Numasawa, H.; Terashima, Y.; Hirano, Y. [Department of Physics, College of Science and Technology, Nihon University, Tokyo 101-8308 (Japan); Hirose, A. [Plasma Physics Laboratory, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2 (Canada)

2010-10-15

A compact and repetitively driven plasma source has been developed by utilizing a magnetized coaxial plasma gun (MCPG) for diagnostics requiring deep penetration of a large amount of neutral flux. The system consists of a MCPG 95mm in length with a DN16 ConFlat connection port and an insulated gate bipolar transistor (IGBT) inverter power unit. The power supply consists of an array of eight IGBT units and is able to switch the discharge on and off at up to 10 kV and 600 A with a maximum repetitive frequency of 10 kHz. Multiple short duration discharge pulses maximize acceleration efficiency of the plasmoid. In the case of a 10 kHz operating frequency, helium-plasmoids in the velocity range of 20 km/s can be achieved.

A compact and continuously driven supersonic plasma and neutral source.

Science.gov (United States)

Asai, T; Itagaki, H; Numasawa, H; Terashima, Y; Hirano, Y; Hirose, A

2010-10-01

A compact and repetitively driven plasma source has been developed by utilizing a magnetized coaxial plasma gun (MCPG) for diagnostics requiring deep penetration of a large amount of neutral flux. The system consists of a MCPG 95mm in length with a DN16 ConFlat connection port and an insulated gate bipolar transistor (IGBT) inverter power unit. The power supply consists of an array of eight IGBT units and is able to switch the discharge on and off at up to 10 kV and 600 A with a maximum repetitive frequency of 10 kHz. Multiple short duration discharge pulses maximize acceleration efficiency of the plasmoid. In the case of a 10 kHz operating frequency, helium-plasmoids in the velocity range of 20 km/s can be achieved.

Advantages of traveling wave resonant antennas for fast wave heating systems

International Nuclear Information System (INIS)

Phelps, D.A.; Callis, R.W.; Grassie, J.S. de

1997-04-01

The resilience of a maximally flat externally coupled traveling wave antenna (TWA) is contrasted with the sensitivity of a simple directly driven resonant loop array to vacuum and plasma conditions in DIII-D. We find a unique synergy between standing and traveling wave resonant TWA components. This synergy extends TWA operation to several passbands between 60 and 120 MHZ, provides 60 degrees- 120 degrees tunability between elements within a 1-2 MHZ bandwidth and permits efficient and continuous operation during ELMing H-mode

Trigger mechanism for the abrupt loss of energetic ions in magnetically confined plasmas.

Science.gov (United States)

Ida, K; Kobayashi, T; Yoshinuma, M; Akiyama, T; Tokuzawa, T; Tsuchiya, H; Itoh, K; Itoh, S-I

2018-02-12

Interaction between a quasi-stable stationary MHD mode and a tongue-shaped deformation is observed in the toroidal plasma with energetic particle driven MHD bursts. The quasi-stable stationary 1/1 MHD mode with interchange parity appears near the resonant rational surface of q = 1 between MHD bursts. The tongue-shaped deformation rapidly appears at the non-resonant non-rational surface as a localized large plasma displacement and then collapses (tongue event). It curbs the stationary 1/1 MHD mode and then triggers the collapse of energetic particle and magnetic field reconnection. The rotating 1/1 MHD mode with tearing parity at the q = 1 resonant surface, namely, the MHD burst, is excited after the tongue event.

Study of selective heating at ion cyclotron resonance for the plasma separation process

Science.gov (United States)

Compant La Fontaine, A.; Pashkovsky, V. G.

1995-12-01

The plasma separation process by ion cyclotron resonance heating (ICRH) is studied both theoretically and experimentally on two devices: the first one called ERIC (Ion Cyclotron Resonance Experiment) at Saclay (France) [P. Louvet, Proceedings of the 2nd Workshop on Separation Phenomena in Liquids and Gases, Versailles, France, 1989, edited by P. Louvet, P. Noe, and Soubbaramayer (Centre d'Etudes Nucléaires de Saclay and Cité Scientifique Parcs et Technopoles, Ile de France Sud, France, 1989), Vol. 1, p. 5] and the other one named SIRENA at the Kurchatov Institute, Moscow, Russia [A. I. Karchevskii et al., Plasma Phys. Rep. 19, 214 (1993)]. The radio frequency (RF) transversal magnetic field is measured by a magnetic probe both in plasma and vacuum and its Fourier spectrum versus the axial wave number kz is obtained. These results are in agreement with the electromagnetic (EM) field calculation model based on resolution of Maxwell equations by a time-harmonic scheme studied here. Various axial boundary conditions models used to compute the EM field are considered. The RF magnetic field is weakly influenced by the plasma while the electric field components are strongly disturbed due to space-charge effects. In the plasma the transversal electric field is enhanced and the kz spectrum is narrower than in vacuum. The calculation of the resonant isotope heating is made by the Runge-Kutta method. The influence of ion-ion collisions, inhomogeneity of the static magnetic field B0, and the RF transversal magnetic field component on the ion acceleration is examined. These results are successfully compared with experiments of a minor isotope 44Ca heating measurements, made with an energy analyzer.

Influence of external resonant magnetic perturbation field on edge plasma of small tokamak HYBTOK-II

Energy Technology Data Exchange (ETDEWEB)

Hayashi, Y., E-mail: hayashi-yuki13@ees.nagoya-u.ac.jp [Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Suzuki, Y.; Ohno, N. [Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Okamoto, M. [Ishikawa National College of Technology, Kitachujo, Tsubata-cho, Kahoku-gun, Ishikawa 929-0392 (Japan); Kikuchi, Y. [University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280 (Japan); Sakakibara, S.; Watanabe, K.; Takemura, Y. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292 (Japan)

2015-08-15

Radial profile of externally applied resonant magnetic perturbation (RMP) field with mode numbers of m = 6 and n = 2 in a small tokamak device HYBTOK-II have been investigated using a magnetic probe array, which is able to measure the radial profile of magnetic field perturbation induced by applying RMP. Results of RMP penetration into the plasma show that the RMP decreased toward the plasma center, while they were amplified around the resonant surface with a safety factor q = 3 due to the formation of magnetic islands. This suggests that RMP fields for controlling edge plasmas may trigger some kind of MHD instabilities. In addition, simulation results, based on a linearized four-field model, which agrees with the experimental ones, indicates that the penetration and amplification process of RMP strongly depend on a Doppler-shifted frequency between the RMP and plasma rotation.

Resonant Alfven wave instabilities driven by streaming fast particles

International Nuclear Information System (INIS)

Zachary, A.

1987-01-01

A plasma simulation code is used to study the resonant interactions between streaming ions and Alfven waves. The medium which supports the Alfven waves is treated as a single, one-dimensional, ideal MHD fluid, while the ions are treated as kinetic particles. The code is used to study three ion distributions: a cold beam; a monoenergetic shell; and a drifting distribution with a power-law dependence on momentum. These distributions represent: the field-aligned beams upstream of the earth's bow shock; the diffuse ions upstream of the bow shock; and the cosmic ray distribution function near a supernova remnant shock. 92 refs., 31 figs., 12 tabs

Trapped Electron Mode Turbulence Driven Intrinsic Rotation in Tokamak Plasmas

International Nuclear Information System (INIS)

Wang, W.X.; Hahm, T.S.; Ethier, S.; Zakharov, L.E.

2011-01-01

Recent progress from global gyrokinetic simulations in understanding the origin of intrinsic rotation in toroidal plasmas is reported with emphasis on electron thermal transport dominated regimes. The turbulence driven intrinsic torque associated with nonlinear residual stress generation by the fluctuation intensity and the intensity gradient in the presence of zonal flow shear induced asymmetry in the parallel wavenumber spectrum is shown to scale close to linearly with plasma gradients and the inverse of the plasma current. These results qualitatively reproduce empirical scalings of intrinsic rotation observed in various experiments. The origin of current scaling is found to be due to enhanced kll symmetry breaking induced by the increased radial variation of the safety factor as the current decreases. The physics origin for the linear dependence of intrinsic torque on pressure gradient is that both turbulence intensity and the zonal flow shear, which are two key ingredients for driving residual stress, increase with the strength of turbulence drive, which is R0/LTe and R0/Lne for the trapped electron mode.

Neutron Generation by Laser-Driven Spherically Convergent Plasma Fusion

Science.gov (United States)

Ren, G.; Yan, J.; Liu, J.; Lan, K.; Chen, Y. H.; Huo, W. Y.; Fan, Z.; Zhang, X.; Zheng, J.; Chen, Z.; Jiang, W.; Chen, L.; Tang, Q.; Yuan, Z.; Wang, F.; Jiang, S.; Ding, Y.; Zhang, W.; He, X. T.

2017-04-01

We investigate a new laser-driven spherically convergent plasma fusion scheme (SCPF) that can produce thermonuclear neutrons stably and efficiently. In the SCPF scheme, laser beams of nanosecond pulse duration and 1 014- 1 015 W /cm2 intensity uniformly irradiate the fuel layer lined inside a spherical hohlraum. The fuel layer is ablated and heated to expand inwards. Eventually, the hot fuel plasmas converge, collide, merge, and stagnate at the central region, converting most of their kinetic energy to internal energy, forming a thermonuclear fusion fireball. With the assumptions of steady ablation and adiabatic expansion, we theoretically predict the neutron yield Yn to be related to the laser energy EL, the hohlraum radius Rh, and the pulse duration τ through a scaling law of Yn∝(EL/Rh1.2τ0.2 )2.5. We have done experiments at the ShengGuangIII-prototype facility to demonstrate the principle of the SCPF scheme. Some important implications are discussed.

Behavior of Excited Argon Atoms in Inductively Driven Plasmas

CERN Document Server

Hebner, G A

1999-01-01

Laser induced fluorescence has been used to measure the spatial distribution of the two lowest energy argon excited states, 1s sub 5 and 1s sub 4 , in inductively driven plasmas containing argon, chlorine and boron trichloride. The behavior of the two energy levels with plasma conditions was significantly different, probably because the 1s sub 5 level is metastable and the 1s sub 4 level is radiatively coupled to the ground state but is radiation trapped. The argon data is compared with a global model to identify the relative importance of processes such as electron collisional mixing and radiation trapping. The trends in the data suggest that both processes play a major role in determining the excited state density. At lower rfpower and pressure, excited state spatial distributions in pure argon were peaked in the center of the discharge, with an approximately Gaussian profile. However, for the highest rfpowers and pressures investigated, the spatial distributions tended to flatten in the center of the disch...

AWAKE Design Report: A Proton-Driven Plasma Wakefield Acceleration Experiment at CERN

CERN Document Server

Caldwell, A; Lotov, K; Muggli, P; Wing, M

2013-01-01

The AWAKE Collaboration has been formed in order to demonstrate proton driven plasma wakefield acceleration for the first time. This technology could lead to future colliders of high energy but of a much reduced length compared to proposed linear accelerators. The SPS proton beam in the CNGS facility will be injected into a 10m plasma cell where the long proton bunches will be modulated into significantly shorter micro-bunches. These micro-bunches will then initiate a strong wakefield in the plasma with peak fields above 1 GV/m that will be harnessed to accelerate a bunch of electrons from about 20MeV to the GeV scale within a few meters. The experimental program is based on detailed numerical simulations of beam and plasma interactions. The main accelerator components, the experimental area and infrastructure required as well as the plasma cell and the diagnostic equipment are discussed in detail. First protons to the experiment are expected at the end of 2015 and this will be followed by an initial 3–4 ye...

Laser-plasma interaction at 10.6 microns

International Nuclear Information System (INIS)

Jones, R.D.; Kindel, J.M.

1983-01-01

The absorption mechanisms at 10.6μm are considered. Given our best theoretical knowledge, at high intensity, CO 2 absorption is a combination of resonant absorption, critical surface decay processes (rippling), and forward and backward Raman scattering. At low intensities (less than 10 14 W/cm 2 ), in short pulse CO 2 experiments, resonant absorption is believed to dominate. The properties of the self generated magnetic fields are considered. These fields greatly affect the hot electron preheat, the lateral transport of energy along the surface of the target, and the enhanced plasma blowoff. And finally, the properties of the enhanced plasma blowoff will be discussed. In directly driven targets, this blowoff represents an energy loss. It has been suggested, however, that the blowoff itself can be used to drive targets

Observation of plasma rotation driven by static nonaxisymmetric magnetic fields in a tokamak.

Science.gov (United States)

Garofalo, A M; Burrell, K H; DeBoo, J C; deGrassie, J S; Jackson, G L; Lanctot, M; Reimerdes, H; Schaffer, M J; Solomon, W M; Strait, E J

2008-11-07

We present the first evidence for the existence of a neoclassical toroidal rotation driven in a direction counter to the plasma current by nonaxisymmetric, nonresonant magnetic fields. At high beta and with large injected neutral beam momentum, the nonresonant field torque slows down the plasma toward the neoclassical "offset" rotation rate. With small injected neutral beam momentum, the toroidal rotation is accelerated toward the offset rotation, with resulting improvement in the global energy confinement time. The observed magnitude, direction, and radial profile of the offset rotation are consistent with neoclassical theory predictions.

Fullerene-rare gas mixed plasmas in an electron cyclotron resonance ion source

Energy Technology Data Exchange (ETDEWEB)

Asaji, T., E-mail: asaji@oshima-k.ac.jp; Ohba, T. [Oshima National College of Maritime Technology, 1091-1 Komatsu, Suo-oshima, Oshima, Yamaguchi 742-2193 (Japan); Uchida, T.; Yoshida, Y. [Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585 (Japan); Minezaki, H.; Ishihara, S. [Graduate School of Engineering, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585 (Japan); Racz, R.; Biri, S. [Institute of Nuclear Research (ATOMKI), H-4026 Debrecen, Bem Tér 18/c (Hungary); Muramatsu, M.; Kitagawa, A. [National Institute of Radiological Sciences (NIRS), 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Kato, Y. [Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan)

2014-02-15

A synthesis technology of endohedral fullerenes such as Fe@C{sub 60} has developed with an electron cyclotron resonance (ECR) ion source. The production of N@C{sub 60} was reported. However, the yield was quite low, since most fullerene molecules were broken in the ECR plasma. We have adopted gas-mixing techniques in order to cool the plasma and then reduce fullerene dissociation. Mass spectra of ion beams extracted from fullerene-He, Ar or Xe mixed plasmas were observed with a Faraday cup. From the results, the He gas mixing technique is effective against fullerene destruction.

Field-aligned plasma-potential structure formed by local electron cyclotron resonance

International Nuclear Information System (INIS)

Hatakeyama, Rikizo; Kaneko, Toshiro; Sato, Noriyoshi

2001-01-01

The significance of basic experiments on field-aligned plasma-potential structure formed by local electron cyclotron resonance (ECR) is claimed based on the historical development of the investigation on electric double layer and electrostatic potential confinement of open-ended fusion-oriented plasmas. In the presence of a single ECR point in simple mirror-type configurations of magnetic field, a potential dip (thermal barrier) appears around this point, being followed by a subsequent potential hump (plug potential) along a collisionless plasma flow. The observed phenomenon gives a clear-cut physics to the formation of field-aligned plug potential with thermal barrier, which is closely related to the double layer formation triggered by a negative dip. (author)

Curvature-driven instabilities in the Elmo Bumpy Torus (EBT)

International Nuclear Information System (INIS)

Abe, H.; Spong, D.A.; Antonsen, T.M. Jr.; Tsang, K.T.; Nguyen, K.T.

1982-01-01

Curvature-driven instabilities are analyzed for an EBT configuration which consists of plasma interacting with a hot electron ring whose drift frequencies are larger than the growth rates predicted from conventional magnetohydrodynamic (MHD) theory. Stability criteria are obtained for five possible modes: the conventional hot electron interchange, a high-frequency hot electron interchange (at frequencies greater than the ion-cyclotron frequency), a compressional instability, a background plasma interchange, and an interacting pressure-driven interchange. A wide parameter regime for stable operation is found, which, however, severely deteriorates for a band of intermediate mode numbers. Finite Larmor radius effects can eliminate this deterioration; moreover, all short-wavelength curvature-driven modes are stabilized if the hot electron Larmor radius rho/sub h/ satisfies (kappa/sub perpendicular/rho/sub h/) 2 > 2Δ/[Rβ/sub h/(1 + P'/sub parallel//P'/sub perpendicular/)], where kappa/sub perpendicular/ is the transverse wavenumber, Δ is the ring half-width, R is the mid-plane radius of curvature, β/sub h/ is the hot electron beta value, and P' is the pressure gradient. Resonant wave-particle instabilities predicted by a new low frequency variational principle show that a variety of remnant instabilities may still persist

Design study of electron cyclotron resonance-ion plasma accelerator for heavy ion cancer therapy

International Nuclear Information System (INIS)

Inoue, T.; Sugimoto, S.; Sasai, K.; Hattori, T.

2014-01-01

Electron Cyclotron Resonance-Ion Plasma Accelerator (ECR-IPAC) device, which theoretically can accelerate multiple charged ions to several hundred MeV with short acceleration length, has been proposed. The acceleration mechanism is based on the combination of two physical principles, plasma electron ion adiabatic ejection (PLEIADE) and Gyromagnetic Autoresonance (GYRAC). In this study, we have designed the proof of principle machine ECR-IPAC device and simulated the electromagnetic field distribution generating in the resonance cavity. ECR-IPAC device consisted of three parts, ECR ion source section, GYRAC section, and PLEIADE section. ECR ion source section and PLEIADE section were designed using several multi-turn solenoid coils and sextupole magnets, and GYRAC section was designed using 10 turns coil. The structure of ECR-IPAC device was the cylindrical shape, and the total length was 1024 mm and the maximum diameter was 580 mm. The magnetic field distribution, which maintains the stable acceleration of plasma, was generated on the acceleration center axis throughout three sections. In addition, the electric field for efficient acceleration of electrons was generated in the resonance cavity by supplying microwave of 2.45 GHz

A solid-state nuclear magnetic resonance study of post-plasma reactions in organosilicone microwave plasma-enhanced chemical vapor deposition (PECVD) coatings.

Science.gov (United States)

Hall, Colin J; Ponnusamy, Thirunavukkarasu; Murphy, Peter J; Lindberg, Mats; Antzutkin, Oleg N; Griesser, Hans J

2014-06-11

Plasma-polymerized organosilicone coatings can be used to impart abrasion resistance and barrier properties to plastic substrates such as polycarbonate. Coating rates suitable for industrial-scale deposition, up to 100 nm/s, can be achieved through the use of microwave plasma-enhanced chemical vapor deposition (PECVD), with optimal process vapors such as tetramethyldisiloxane (TMDSO) and oxygen. However, it has been found that under certain deposition conditions, such coatings are subject to post-plasma changes; crazing or cracking can occur anytime from days to months after deposition. To understand the cause of the crazing and its dependence on processing plasma parameters, the effects of post-plasma reactions on the chemical bonding structure of coatings deposited with varying TMDSO-to-O2 ratios was studied with (29)Si and (13)C solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) using both single-pulse and cross-polarization techniques. The coatings showed complex chemical compositions significantly altered from the parent monomer. (29)Si MAS NMR spectra revealed four main groups of resonance lines, which correspond to four siloxane moieties (i.e., mono (M), di (D), tri (T), and quaternary (Q)) and how they are bound to oxygen. Quantitative measurements showed that the ratio of TMDSO to oxygen could shift the chemical structure of the coating from 39% to 55% in Q-type bonds and from 28% to 16% for D-type bonds. Post-plasma reactions were found to produce changes in relative intensities of (29)Si resonance lines. The NMR data were complemented by Fourier transform infrared (FTIR) spectroscopy. Together, these techniques have shown that the bonding environment of Si is drastically altered by varying the TMDSO-to-O2 ratio during PECVD, and that post-plasma reactions increase the cross-link density of the silicon-oxygen network. It appears that Si-H and Si-OH chemical groups are the most susceptible to post-plasma reactions. Coatings produced at a

Experimental Verification of Isotropic Radiation from a Coherent Dipole Source via Electric-Field-Driven LC Resonator Metamaterials

Science.gov (United States)

Tichit, Paul-Henri; Burokur, Shah Nawaz; Qiu, Cheng-Wei; de Lustrac, André

2013-09-01

It has long been conjectured that isotropic radiation by a simple coherent source is impossible due to changes in polarization. Though hypothetical, the isotropic source is usually taken as the reference for determining a radiator’s gain and directivity. Here, we demonstrate both theoretically and experimentally that an isotropic radiator can be made of a simple and finite source surrounded by electric-field-driven LC resonator metamaterials designed by space manipulation. As a proof-of-concept demonstration, we show the first isotropic source with omnidirectional radiation from a dipole source (applicable to all distributed sources), which can open up several possibilities in axion electrodynamics, optical illusion, novel transformation-optic devices, wireless communication, and antenna engineering. Owing to the electric- field-driven LC resonator realization scheme, this principle can be readily applied to higher frequency regimes where magnetism is usually not present.

Study of selective heating at ion cyclotron resonance for the plasma separation process

International Nuclear Information System (INIS)

Compant La Fontaine, A.; Pashkovsky, V.G.

1995-01-01

The plasma separation process by ion cyclotron resonance heating (ICRH) is studied both theoretically and experimentally on two devices: the first one called ERIC (Ion Cyclotron Resonance Experiment) at Saclay (France) [P. Louvet, Proceedings of the 2nd Workshop on Separation Phenomena in Liquids and Gases, Versailles, France, 1989, edited by P. Louvet, P. Noe, and Soubbaramayer (Centre d'Etudes Nucleaires de Saclay and Cite Scientifique Parcs et Technopoles, Ile de France Sud, France, 1989), Vol. 1, p. 5] and the other one named SIRENA at the Kurchatov Institute, Moscow, Russia [A. I. Karchevskii et al., Plasma Phys. Rep. 19, 214 (1993)]. The radio frequency (RF) transversal magnetic field is measured by a magnetic probe both in plasma and vacuum and its Fourier spectrum versus the axial wave number k z is obtained. These results are in agreement with the electromagnetic (EM) field calculation model based on resolution of Maxwell equations by a time-harmonic scheme studied here. Various axial boundary conditions models used to compute the EM field are considered. The RF magnetic field is weakly influenced by the plasma while the electric field components are strongly disturbed due to space-charge effects. In the plasma the transversal electric field is enhanced and the k z spectrum is narrower than in vacuum. The calculation of the resonant isotope heating is made by the Runge--Kutta method. The influence of ion--ion collisions, inhomogeneity of the static magnetic field B 0 , and the RF transversal magnetic field component on the ion acceleration is examined. These results are successfully compared with experiments of a minor isotope 44 Ca heating measurements, made with an energy analyzer. copyright 1995 American Institute of Physics

Plasma potential in a magnetic mirror with electron-cyclotron-resonance heating

International Nuclear Information System (INIS)

Smith, P.K.

1983-01-01

Experimental and theoretical studies of the ECRH plasma in the University of Wisconsin DE Machine magnetic mirror have been undertaken. Typical plasma parameters in these experiments were T/sub e/ - 10 to 30 eV, T/sub i/ - 4 eV, V/sub po/ (plasma potential at midplane) - 20 to 50 V, midplane plasma density n 0 - 10 16 m - 3 , B 0 (magnetic field strength on axis at midplane) - .005 to .01 T, mirror ratio R - 5 to 20. The principal experimental findings were the appearance of strong density peaks (approx. 2 x background) and notable V/sub f/ dips (approx. kT/sub e//e) in a narrow (approx. 1 cm) region near the axial positions of cyclotron resonance. The properties of these dips do not change greatly over the range of operating parameters, but are narrower at higher pressures

4d--4f emission resonances in laser-produced plasmas

International Nuclear Information System (INIS)

O'Sullivan, G.; Carroll, P.K.

1981-01-01

Using targets containing compounds of the elements cesium through lutetium, we studied the spectra of laser-produced plasmas in the grazing-incidence region from 40 to 200 A. The spectra are characterized by strong regions of resonancelike emission extending typically over 9--18 eV. With increasing Z, the spectra show certain systematic variations in character and move monotonically toward shorter wavelengths. From a collisional-radiative plasma model, the ion stages responsible for the emision are identified as VIII through XVI. The resonances are attributed to 4-4f transitions that, because Dn = 0, tend to overlap for different ion stages of the same element

Electron cyclotron resonance ion source plasma characterization by X-ray spectroscopy and X-ray imaging

Energy Technology Data Exchange (ETDEWEB)

Mascali, David, E-mail: davidmascali@lns.infn.it; Castro, Giuseppe; Celona, Luigi; Neri, Lorenzo; Gammino, Santo [INFN–Laboratori Nazionali del Sud, Via S. Sofia 62, 95125 Catania (Italy); Biri, Sándor; Rácz, Richárd; Pálinkás, József [Institute for Nuclear Research (Atomki), Hungarian Academy of Sciences, Bem tér 18/c, H-4026 Debrecen (Hungary); Caliri, Claudia [INFN–Laboratori Nazionali del Sud, Via S. Sofia 62, 95125 Catania (Italy); Università degli Studi di Catania, Dip.to di Fisica e Astronomia, via Santa Sofia 64, 95123 Catania (Italy); Romano, Francesco Paolo [INFN–Laboratori Nazionali del Sud, Via S. Sofia 62, 95125 Catania (Italy); CNR, Istituto per i Beni Archeologici e Monumentali, Via Biblioteca 4, 95124 Catania (Italy); Torrisi, Giuseppe [INFN–Laboratori Nazionali del Sud, Via S. Sofia 62, 95125 Catania (Italy); Università Mediterranea di Reggio Calabria, DIIES, Via Graziella, I-89100 Reggio Calabria (Italy)

2016-02-15

An experimental campaign aiming to investigate electron cyclotron resonance (ECR) plasma X-ray emission has been recently carried out at the ECRISs—Electron Cyclotron Resonance Ion Sources laboratory of Atomki based on a collaboration between the Debrecen and Catania ECR teams. In a first series, the X-ray spectroscopy was performed through silicon drift detectors and high purity germanium detectors, characterizing the volumetric plasma emission. The on-purpose developed collimation system was suitable for direct plasma density evaluation, performed “on-line” during beam extraction and charge state distribution characterization. A campaign for correlating the plasma density and temperature with the output charge states and the beam intensity for different pumping wave frequencies, different magnetic field profiles, and single-gas/gas-mixing configurations was carried out. The results reveal a surprisingly very good agreement between warm-electron density fluctuations, output beam currents, and the calculated electromagnetic modal density of the plasma chamber. A charge-coupled device camera coupled to a small pin-hole allowing X-ray imaging was installed and numerous X-ray photos were taken in order to study the peculiarities of the ECRIS plasma structure.

Electric dipole spin resonance in a quantum spin dimer system driven by magnetoelectric coupling

Science.gov (United States)

Kimura, Shojiro; Matsumoto, Masashige; Akaki, Mitsuru; Hagiwara, Masayuki; Kindo, Koichi; Tanaka, Hidekazu

2018-04-01

In this Rapid Communication, we propose a mechanism for electric dipole active spin resonance caused by spin-dependent electric polarization in a quantum spin gapped system. This proposal was successfully confirmed by high-frequency electron spin resonance (ESR) measurements of the quantum spin dimer system KCuCl3. ESR measurements by an illuminating linearly polarized electromagnetic wave reveal that the optical transition between the singlet and triplet states in KCuCl3 is driven by an ac electric field. The selection rule of the observed transition agrees with the calculation by taking into account spin-dependent electric polarization. We suggest that spin-dependent electric polarization is effective in achieving fast control of quantum spins by an ac electric field.

Plasma microinstabilities driven by loss-cone distributions

International Nuclear Information System (INIS)

Summers, D.; Thorne, R.M.

1995-01-01

Electromagnetic and electrostatic instabilities driven by loss-cone particle distributions have been invoked to explain a variety of plasma phenomena observed in space and in the laboratory. In this paper we analyse how the loss-cone feature (as determined by the loss-cone index or indices) influences the growth of such instabilities in a fully ionized, homogeneous, hot plasma in a uniform magnetic field. Specifically, we consider three loss-cone distributions: a generalized Lorentzian (kappa) loss-cone distribution, the Dory-Guest-Harris distribution and the Ashour-Abdalla-Kennel distribution (involving a subtracted Maxwellian). Our findings are common to all three distributions. We find that, for parallel propagation, electromagnetic instabilities are only affected by the loss-cone indices in terms of their occurrence in the temperature anisotropy. However, for oblique propagation, even including propagation at small angles to the ambient magnetic field, the loss-cone indices do independently affect the growth of instabilities for electromagnetic waves, in contrast to certain claims in the literature. For electrostatic waves such that 1/2(κ perpendicular to ρ L σ 2 L σ is the Larmor radius for particle species σ, we find that the loss-cone indices only enter the dispersion equation via the temperature anisotropy, and so in this case the loss-cone feature and perpendicular effective thermal speed do not independently affect wave growth. (Author)

High resolution detection and excitation of resonant magnetic perturbations in a wall-stabilized tokamak

Energy Technology Data Exchange (ETDEWEB)

Maurer, David A. [Physics Department, Auburn University, Auburn, Alabama 36849 (United States); Shiraki, Daisuke; Levesque, Jeffrey P.; Bialek, James; Angelini, Sarah; Byrne, Patrick; DeBono, Bryan; Hughes, Paul; Mauel, Michael E.; Navratil, Gerald A.; Peng Qian; Rhodes, Dov; Rath, Nickolaus; Stoafer, Christopher [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

2012-05-15

We report high-resolution detection of the 3D plasma magnetic response of wall-stabilized tokamak discharges in the High Beta Tokamak-Extended Pulse [T. H. Ivers et al., Phys. Plasmas 3, 1926 (1996)] device. A new adjustable conducting wall has been installed on HBT-EP made up of 20 independent, movable, wall segments instrumented with three distinct sets of 40 modular coils that can be independently driven to generate a wide variety of magnetic perturbations. High-resolution detection of the plasma response is made with 216 poloidal and radial magnetic sensors that have been located and calibrated with high-accuracy. Static and dynamic plasma responses to resonant and non-resonant magnetic perturbations are observed through measurement of the step-response following a rapid change in the toroidal phase of the applied perturbations. Biorthogonal decomposition of the full set of magnetic sensors clearly defines the structures of naturally occurring external kinks as being composed of independent m/n = 3/1 and 6/2 modes. Resonant magnetic perturbations were applied to discharges with pre-existing, saturated m/n = 3/1 external kink mode activity. This m/n = 3/1 kink mode was observed to lock to the applied perturbation field. During this kink mode locked period, the plasma resonant response is characterized by a linear, a saturated, and a disruptive plasma regime dependent on the magnitude of the applied field and value of the edge safety factor and plasma rotation.

Ion temperature gradient driven mode in presence of transverse velocity shear in magnetized plasmas

DEFF Research Database (Denmark)

Chakrabarti, N.; Juul Rasmussen, J.; Michelsen, Poul

2005-01-01

The effect of sheared poloidal flow on the toroidal branch of the ion temperature gradient driven mode of magnetized nonuniform plasma is studied. A novel "nonmodal" calculation is used to analyze the problem. It is shown that the transverse shear flow considerably reduced the growth...

Investigation and application of microwave electron cyclotron resonance plasma physical vapour deposition

International Nuclear Information System (INIS)

Ren Zhaoxing; Sheng Yanya; Shi Yicai; Wen Haihu; Cao Xiaowen

1991-06-01

The evaporating deposition of Ti film and Cu film by using microwave electron cyclotron resonance (ECR) technique was investigated. It deposition rate was about 50 nm/min and the temperature of the substrate was 50∼150 deg C. The thin amorphous films with strong adherent force were obtained. The sputtering deposition with ECR plasma was studied by employing higher plasma density and ionicity and negative substrate potential to make YBaCuO superconducting film. Its film was compact and amorphous with a thickness of 1.0 μm and the deposition rate was about 10 nm/min. The results show that this technique can initiate a high density and high ionicity plasma at lower gas pressure (10 -2 ∼10 -3 Pa). This plasma is the most suitable plasma source in thin film deposition process and surface treatment technique

Application of laser resonance scattering to the study of high-temperature plasma-wall interaction

International Nuclear Information System (INIS)

Maeda, Mitsuo; Muraoka, Katsunori; Hamamoto, Makoto; Akazaki, Masanori; Miyazoe, Yasushi

1981-01-01

Studies on laser resonance scattering and its application to the study of high-temperature plasma-wall interaction are reviewed. The application of dye laser beam to resonant scattering method has been developed. This method is able to detect low density atoms. The fluorescent photon counts can be estimated for a two-level system and a three-level system. The S/N ratio, Which is in close connection with the detection limit, has been estimated. The doppler effect due to the thermal motion of atoms is taken into consideration. The calibration of the absolute number of atoms is necessary. Tunable coherent light is used as the light source for resonance scattering method. This is able to excite atoms strongly and to increase the detection efficiency. As dye lasers, a N 2 laser, a YAG laser, and a KrF excimer laser have been studied. In VUV region, rare gas or rare gas halide lasers can be used. The strong output power can be expected when the resonance lines of atoms meet the synchronizing region of the excimer laser. The resonance scattering method is applied to the detection of impurity metal atoms in plasma. The studies of laser systems for the detection of hydrogen atoms are also in progress. (Kato, T.)

Fast ion stabilization of the ion temperature gradient driven modes in the Joint European Torus hybrid-scenario plasmas: a trigger mechanism for internal transport barrier formation

Energy Technology Data Exchange (ETDEWEB)

Romanelli, M; Zocco, A [Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon, OX14 3DB (United Kingdom); Crisanti, F, E-mail: Michele.Romanelli@ccfe.ac.u [Associazione Euratom-ENEA sulla Fusione, C.R. Frascati, Frascati (Italy)

2010-04-15

Understanding and modelling turbulent transport in thermonuclear fusion plasmas are crucial for designing and optimizing the operational scenarios of future fusion reactors. In this context, plasmas exhibiting state transitions, such as the formation of an internal transport barrier (ITB), are particularly interesting since they can shed light on transport physics and offer the opportunity to test different turbulence suppression models. In this paper, we focus on the modelling of ITB formation in the Joint European Torus (JET) [1] hybrid-scenario plasmas, where, due to the monotonic safety factor profile, magnetic shear stabilization cannot be invoked to explain the transition. The turbulence suppression mechanism investigated here relies on the increase in the plasma pressure gradient in the presence of a minority of energetic ions. Microstability analysis of the ion temperature gradient driven modes (ITG) in the presence of a fast-hydrogen minority shows that energetic ions accelerated by the ion cyclotron resonance heating (ICRH) system (hydrogen, n{sub H,fast}/n{sub D,thermal} up to 10%, T{sub H,fast}/T{sub D,thermal} up to 30) can increase the pressure gradient enough to stabilize the ITG modes driven by the gradient of the thermal ions (deuterium). Numerical analysis shows that, by increasing the temperature of the energetic ions, electrostatic ITG modes are gradually replaced by nearly electrostatic modes with tearing parity at progressively longer wavelengths. The growth rate of the microtearing modes is found to be lower than that of the ITG modes and comparable to the local E x B-velocity shearing rate. The above mechanism is proposed as a possible trigger for the formation of ITBs in this type of discharges.

Wave driven magnetic reconnection in the Taylor problem

International Nuclear Information System (INIS)

Fitzpatrick, Richard; Bhattacharjee, Amitava; Ma Zhiwei; Linde, Timur

2003-01-01

An improved Laplace transform theory is developed in order to investigate the initial response of a stable slab plasma equilibrium enclosed by conducting walls to a suddenly applied wall perturbation in the so-called Taylor problem. The novel feature of this theory is that it does not employ asymptotic matching. If the wall perturbation is switched on slowly compared to the Alfven time then the plasma response eventually asymptotes to that predicted by conventional asymptotic matching theory. However, at early times there is a compressible Alfven wave driven contribution to the magnetic reconnection rate which is not captured by asymptotic matching theory, and leads to a significant increase in the reconnection rate. If the wall perturbation is switched on rapidly compared to the Alfven time then strongly localized compressible Alfven wave-pulses are generated which bounce backward and forward between the walls many times. Each instance these wave-pulses cross the resonant surface they generate a transient surge in the reconnection rate. The maximum pulse driven reconnection rate can be much larger than that predicted by conventional asymptotic matching theory

Energy balance and transient responses in wave driven plasmas

International Nuclear Information System (INIS)

Rax, J.M.

1987-06-01

In a current-drive experiment with a RF power source, a certain amount of power is absorbed by resonant electrons. From the electrons, energy can flow through four channels: it can be converted into magnetic work when the electron interacts with an electric field, or it can be converted into heat when the electron collides the thermal plasma. In addition, there exists also the conversion of the low frequency RF energy into high frequency non thermal free-free or cyclotron radiation. Efficiencies of these conversions are considered together with the turn-on times of the associated responses

Impact of rotating resonant magnetic perturbation fields on plasma edge electron density and temperature

International Nuclear Information System (INIS)

Stoschus, H.; Schmitz, O.; Frerichs, H.; Reiser, D.; Unterberg, B.; Lehnen, M.; Reiter, D.; Samm, U.; Jakubowski, M.W.

2012-01-01

Rotating resonant magnetic perturbation (RMP) fields impose a characteristic modulation to the edge electron density n e (r, t) and temperature T e (r, t) fields, which depends on the relative rotation f rel between external RMP field and plasma fluid. The n e (r, t) and T e (r, t) fields measured in the edge (r/a = 0.9–1.05) of TEXTOR L-mode plasmas are in close correlation with the local magnetic vacuum topology for low relative rotation f rel = −0.2 kHz. In comparison with the 3D neutral and plasma transport code EMC3-Eirene, this provides substantial experimental evidence that for low relative rotation level and high resonant field amplitudes (normalized radial field strength B r 4/1 /B t =2×10 -3 ), a stochastic edge with a remnant island chain dominated by diffusive transport exists. Radially outside a helical scrape-off layer, the so-called laminar zone embedded into a stochastic domain is found to exist. In contrast for high relative rotation of f rel = 1.8 kHz, the measured modulation of n e is shifted by π/2 toroidally with respect to the modelled vacuum topology. A pronounced flattening in T e (r) and a reduction in n e (r) is measured at the resonant flux surface and represents a clear signature for a magnetic island, which is phase shifted with respect to the vacuum island position. A correlated shift of the laminar zone radially outwards at the very plasma edge is observed suggesting that the actual near-field structure at the perturbation source is determined by the plasma response as well. (paper)

Pressure-driven sound turbulence in a high-β plasma

International Nuclear Information System (INIS)

Stenzel, R.L.

1990-01-01

In a large laboratory plasma [1 m diamx2 m, n e ≤10 12 cm -3 , β 0 ≅15 G, β e =nkT e /(β 0 2 /2μ 0 )≅0.5], strong density fluctuations (δn/n≅50%) near the lower hybrid frequency (ω ce ω ci ) 1/2 are identified as cross-field sound waves (k perpendicular much-gt k parallel , ω/k perpendicular ≅c s ) driven unstable by the electron diamagnetic drift v d =∇pxB/neβ 2 , v d >c s . Wave steepening and refraction saturate the instability. Wave-enhanced transport but insignificant particle acceleration are observed

ELM triggering by energetic particle driven mode in wall-stabilized high-β plasmas

International Nuclear Information System (INIS)

Matsunaga, G.; Aiba, N.; Shinohara, K.; Asakura, N.; Isayama, A.; Oyama, N.

2013-01-01

In the JT-60U high-β plasmas above the no-wall β limit, a triggering of an edge localized mode (ELM) by an energetic particle (EP)-driven mode has been observed. This EP-driven mode is thought to be driven by trapped EPs and it has been named EP-driven wall mode (EWM) on JT-60U (Matsunaga et al 2009 Phys. Rev. Lett. 103 045001). When the EWM appears in an ELMy H-mode phase, ELM crashes are reproducibly synchronized with the EWM bursts. The EWM-triggered ELM has a higher repetition frequency and less energy loss than those of the natural ELM. In order to trigger an ELM by the EP-driven mode, some conditions are thought to be needed, thus an EWM with large amplitude and growth rate, and marginal edge stability. In the scrape-off layer region, several measurements indicate an ion loss induced by the EWM. The ion transport is considered as the EP transport through the edge region. From these observations, the EP contributions to edge stability are discussed as one of the ELM triggering mechanisms. (paper)

Model of charge-state distributions for electron cyclotron resonance ion source plasmas

Directory of Open Access Journals (Sweden)

D. H. Edgell

1999-12-01

Full Text Available A computer model for the ion charge-state distribution (CSD in an electron cyclotron resonance ion source (ECRIS plasma is presented that incorporates non-Maxwellian distribution functions, multiple atomic species, and ion confinement due to the ambipolar potential well that arises from confinement of the electron cyclotron resonance (ECR heated electrons. Atomic processes incorporated into the model include multiple ionization and multiple charge exchange with rate coefficients calculated for non-Maxwellian electron distributions. The electron distribution function is calculated using a Fokker-Planck code with an ECR heating term. This eliminates the electron temperature as an arbitrary user input. The model produces results that are a good match to CSD data from the ANL-ECRII ECRIS. Extending the model to 1D axial will also allow the model to determine the plasma and electrostatic potential profiles, further eliminating arbitrary user input to the model.

Resistive interchange mode destabilized by helically trapped energetic ions and its effects on energetic ions and bulk plasmas

International Nuclear Information System (INIS)

Du, X.D.; Toi, K.; Osakabe, M.

2014-10-01

A resistive interchange mode with bursting behavior and rapid frequency chirping in the range less than 10 kHz is observed for the first time in the magnetic hill region of net current-free, low beta LHD (Large Helical Device) plasmas during high power injection of perpendicular neutral beams. The mode resonates with the precession motion of helically trapped energetic beam ions, following the resonant condition. The radial mode structure is found to be very similar to that of usual pressure-driven interchange mode, of which radial displacement eigenfunction has an even function around the rational surface. This beam driven mode is excited when the beta value of helically trapped energetic ions exceed a certain threshold. The radial transport of helically trapped energetic ions induced by the mode transiently generates significant radial electric field near the plasma peripheral region. Thus generated radial electric field clearly suppresses micro turbulence and improves bulk plasma confinement, suggesting strong flow shear generation. (author)

Response of plasma rotation to resonant magnetic perturbations in J-TEXT tokamak

Science.gov (United States)

Yan, W.; Chen, Z. Y.; Huang, D. W.; Hu, Q. M.; Shi, Y. J.; Ding, Y. H.; Cheng, Z. F.; Yang, Z. J.; Pan, X. M.; Lee, S. G.; Tong, R. H.; Wei, Y. N.; Dong, Y. B.; J-TEXT Team

2018-03-01

The response of plasma toroidal rotation to the external resonant magnetic perturbations (RMP) has been investigated in Joint Texas Experimental Tokamak (J-TEXT) ohmic heating plasmas. For the J-TEXT’s plasmas without the application of RMP, the core toroidal rotation is in the counter-current direction while the edge rotation is near zero or slightly in the co-current direction. Both static RMP experiments and rotating RMP experiments have been applied to investigate the plasma toroidal rotation. The core toroidal rotation decreases to lower level with static RMP. At the same time, the edge rotation can spin to more than 20 km s-1 in co-current direction. On the other hand, the core plasma rotation can be slowed down or be accelerated with the rotating RMP. When the rotating RMP frequency is higher than mode frequency, the plasma rotation can be accelerated to the rotating RMP frequency. The plasma confinement is improved with high frequency rotating RMP. The plasma rotation is decelerated to the rotating RMP frequency when the rotating RMP frequency is lower than the mode frequency. The plasma confinement also degrades with low frequency rotating RMP.

On the plasma confinement by acoustic resonance. An innovation for electrodeless high-pressure discharge lamps

Science.gov (United States)

Courret, Gilles; Nikkola, Petri; Wasterlain, Sébastien; Gudozhnik, Olexandr; Girardin, Michel; Braun, Jonathan; Gavin, Serge; Croci, Mirko; Egolf, Peter W.

2017-08-01

In an applied research project on the development of a pulsed microwave sulfur lamp prototype of 1 kW, we have discovered an amazing phenomenon in which the plasma forms a ball staying at the center of the bulb despite gravity, thus protecting the glass from melting. In this paper, it is shown that this results from an acoustic resonance in a spherical mode. Measurements of the plasma response to short pulses are presented showing beats at the spherical resonance. It is demonstrated that the beats could result from the simultaneous excitation of two normal modes with a frequency difference of approximately 1%. One of the two frequencies matches precisely the microwave pulses repetition, a little below 30 kHz. Thus this one is due to a forced oscillation, whereas the other one is due to a free oscillation. The phase velocity of sound was calculated as a function of temperature in order to find the series of temperatures at which a resonance would occur if the bulb were an isothermal solid sphere. The mean temperature inside the actual bulb was determined from the only doublet of this series, that has characteristic frequencies close enough to cause the observed beats. In addition, one of these two modes has a spherical symmetry that can explain the plasma ball formation. The obtained mean temperature is consistent with the direct measurements on the bulb surface as well as with the temperature in the core of a similar plasma found in the literature. We have also proposed a model of the resonance onset based on the acoustic dispersion and the sound amplification due to electromagnetic coupling.

Resonance-enhanced laser-induced plasma spectroscopy: ambient gas effects

International Nuclear Information System (INIS)

Lui, S.L.; Cheung, N.H.

2003-01-01

When performing laser-induced plasma spectroscopy for elemental analysis, the sensitivity could be significantly enhanced if the plume was resonantly rekindled by a dye laser pulse. The extent of the enhancement was found to depend on the ambient gas. Air, nitrogen, helium, argon and xenon at pressures ranging from vacuum to 1 bar were investigated. In vacuum, the analyte signal was boosted because of reduced cooling, but it soon decayed as the plume freely expanded. By choosing the right ambient gas at the right pressure, the expanding plume could be confined as well as thermally insulated to maximize the analyte signal. For instance, an ambient of 13 mbar xenon yielded a signal-to-noise ratio of 110. That ratio was 53 when the pellet was ablated in air, and decreased further to 5 if the dye laser was tuned off resonance

Half bridge resonant converter for ignition of thermal plasmas

International Nuclear Information System (INIS)

Pena E, L.

1997-01-01

In this work the background, design, implementation and performance of a half bridge resonant converter (HBRC) used as an electronic ignition system for arc plasma torch generation is presented. The significance of the design lies in its simplicity, versatility and low cost. The system operates like a high voltage supply attached to electrodes before gaseous breakdown and like open circuit when electric arc is established. Resonant converter is implemented with a high voltage and high speed power driver intended for control the power MOSFET transistors connected in half bridge topology with L C load. The HBRC operates besides interference into domestic electric supply line (120 V, 60 Hz) as well electric measurement devices. Advantages and limitations of the converter are reviewed. Experimental impedance variation in the medium as a function of frequency operation and some experiences in striking arcs are also presented. (Author)

Dry cleaning of fluorocarbon residues by low-power electron cyclotron resonance hydrogen plasma

CERN Document Server

Lim, S H; Yuh, H K; Yoon Eui Joon; Lee, S I

1988-01-01

A low-power ( 50 W) electron cyclotron resonance hydrogen plasma cleaning process was demonstrated for the removal of fluorocarbon residue layers formed by reactive ion etching of silicon dioxide. The absence of residue layers was confirmed by in-situ reflection high energy electron diffraction and cross-sectional high resolution transmission electron microscopy. The ECR hydrogen plasma cleaning was applied to contact cleaning of a contact string structure, resulting in comparable contact resistance arising during by a conventional contact cleaning procedure. Ion-assisted chemical reaction involving reactive atomic hydrogen species generated in the plasma is attributed for the removal of fluorocarbon residue layers.

Computational study of plasma-assisted photoacoustic response from gold nanoparticles irradiated by off-resonance ultrafast laser

Energy Technology Data Exchange (ETDEWEB)

Hatef, Ali, E-mail: alih@nipissingu.ca; Darvish, Behafarid [Nipissing University, Nipissing Computational Physics Laboratory (NCPL), Department of Computer Science and Mathematics (Canada); Sajjadi, Amir Yousef [Massachusetts General Hospital, Cutaneous Biology Research Center (United States)

2017-02-15

The gold nanoparticles (AuNPs) are capable of enhancing the incident laser field in the form of scattered near field for even an off-resonance irradiation where the incident laser wavelength is far away from the localized surface plasmon resonance (LSPR). If the intensity of the pulse laser is large enough, this capability can be employed to generate a highly localized free electron (plasma) in the vicinity of the particles. The generated plasma can absorb more energy during the pulse, and this energy deposition can be considered as an energy source for structural mechanics calculations in the surrounding media to generate a photoacoustic (PA) signal. To show this, in this paper, we model plasma-mediated PA pressure wave propagation from a 100-nm AuNPs and the surrounding media irradiated by an ultrashort pulse laser. In this model, the AuNP is immersed in water and the laser pulse width is ranging from 70 fs to 2 ps at the wavelength of 800 nm (off-resonance). Our results qualitatively show the substantial impact of the energy deposition in plasma on the PA signal through boosting the pressure amplitudes up to ∼1000 times compared to the conventional approach.

Computational study of plasma-assisted photoacoustic response from gold nanoparticles irradiated by off-resonance ultrafast laser

International Nuclear Information System (INIS)

Hatef, Ali; Darvish, Behafarid; Sajjadi, Amir Yousef

2017-01-01

The gold nanoparticles (AuNPs) are capable of enhancing the incident laser field in the form of scattered near field for even an off-resonance irradiation where the incident laser wavelength is far away from the localized surface plasmon resonance (LSPR). If the intensity of the pulse laser is large enough, this capability can be employed to generate a highly localized free electron (plasma) in the vicinity of the particles. The generated plasma can absorb more energy during the pulse, and this energy deposition can be considered as an energy source for structural mechanics calculations in the surrounding media to generate a photoacoustic (PA) signal. To show this, in this paper, we model plasma-mediated PA pressure wave propagation from a 100-nm AuNPs and the surrounding media irradiated by an ultrashort pulse laser. In this model, the AuNP is immersed in water and the laser pulse width is ranging from 70 fs to 2 ps at the wavelength of 800 nm (off-resonance). Our results qualitatively show the substantial impact of the energy deposition in plasma on the PA signal through boosting the pressure amplitudes up to ∼1000 times compared to the conventional approach.

Toroidal modeling of plasma response and resonant magnetic perturbation field penetration

Czech Academy of Sciences Publication Activity Database

Liu, Y.Q.; Kirk, A.; Sun, Y.; Cahyna, Pavel; Chapman, I.T.; Denner, P.; Fishpool, G.; Garofalo, A.M.; Harrison, J.R.; Nardon, E.

2012-01-01

Roč. 54, č. 12 (2012), s. 124013-124013 ISSN 0741-3335 Institutional research plan: CEZ:AV0Z20430508 Keywords : tokamak * resonant magnetic perturbation * neoclassical toroidal viscosity Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.369, year: 2012 http://iopscience.iop.org/0741-3335/54/12/124013/pdf/0741-3335_54_12_124013.pdf

Resonance parallel viscosity in the banana regime in poloidally rotating tokamak plasmas

International Nuclear Information System (INIS)

Shaing, K.C.; Hsu, C.T.; Dominguez, N.

1994-01-01

Parallel viscosity in the banana regime in a poloidally (ExB) rotating tokamak plasma is calculated to include the effects of orbit squeezing and to allow the poloidal ExB Mach number M p to have a value of order unity. Here, E is the electric field and B is the magnetic field. The effects of orbit squeezing not only modify the size of the particle orbit, but also change the fraction of poloidally trapped particles. Resonance between the particle parallel (to B) speed u and the poloidal component of the ExB velocity can only occur for those particles with energy (v/v t ) 2 >M 2 p (with v the particle speed and v t the thermal speed). Thus, the resonance parallel plasma viscosity in the banana regime decreases exponentially with M 2 p when M 2 p ≥1, and has a local maximum of M 2 p ∼1

Plasma potentials and performance of the advanced electron cyclotron resonance ion source

International Nuclear Information System (INIS)

Xie, Z.Q.; Lyneis, C.M.

1994-01-01

The mean plasma potential was measured on the LBL advanced electron cyclotron resonance (AECR) ion source for a variety of conditions. The mean potentials for plasmas of oxygen, argon, and argon mixed with oxygen in the AECR were determined. These plasma potentials are positive with respect to the plasma chamber wall and are on the order of tens of volts. Electrons injected into the plasma by an electron gun or from an aluminum oxide wall coating with a very high secondary electron emission reduce the plasma potential as does gas mixing. A lower plasma potential in the AECR source coincides with enhanced production of high charged state ions indicating longer ion confinement times. The effect of the extra electrons from external injection or wall coatings is to lower the average plasma potential and to increase the n e τ i of the ECR plasma. With sufficient extra electrons, the need for gas mixing can be eliminated or reduced to a lower level, so the source can operate at lower neutral pressures. A reduction of the neutral pressure decreases charge exchange between ions and neutrals and enhances the production of high charge state ions. An aluminum oxide coating results in the lowest plasma potential among the three methods discussed and the best source performance

Properties of the ion-ion hybrid resonator in fusion plasmas

International Nuclear Information System (INIS)

Morales, George J.

2015-01-01

The project developed theoretical and numerical descriptions of the properties of ion-ion hybrid Alfvn resonators that are expected to arise in the operation of a fusion reactor. The methodology and theoretical concepts were successfully compared to observations made in basic experiments in the LAPD device at UCLA. An assessment was made of the excitation of resonator modes by energetic alpha particles for burning plasma conditions expected in the ITER device. The broader impacts included the generation of basic insight useful to magnetic fusion and space science researchers, defining new avenues for exploration in basic laboratory experiments, establishing broader contacts between experimentalists and theoreticians, completion of a Ph.D. dissertation, and promotion of interest in science through community outreach events and classroom instruction.

The effect of sheared toroidal rotation on pressure driven magnetic islands in toroidal plasmas

Energy Technology Data Exchange (ETDEWEB)

Hegna, C. C. [Departments of Engineering Physics and Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

2016-05-15

The impact of sheared toroidal rotation on the evolution of pressure driven magnetic islands in tokamak plasmas is investigated using a resistive magnetohydrodynamics model augmented by a neoclassical Ohm's law. Particular attention is paid to the asymptotic matching data as the Mercier indices are altered in the presence of sheared flow. Analysis of the nonlinear island Grad-Shafranov equation shows that sheared flows tend to amplify the stabilizing pressure/curvature contribution to pressure driven islands in toroidal tokamaks relative to the island bootstrap current contribution. As such, sheared toroidal rotation tends to reduce saturated magnetic island widths.

Transition to Collisionless Ion-Temperature-Gradient-Driven Plasma Turbulence: A Dynamical Systems Approach

International Nuclear Information System (INIS)

Kolesnikov, R.A.; Krommes, J.A.

2005-01-01

The transition to collisionless ion-temperature-gradient-driven plasma turbulence is considered by applying dynamical systems theory to a model with 10 degrees of freedom. The study of a four-dimensional center manifold predicts a 'Dimits shift' of the threshold for turbulence due to the excitation of zonal flows and establishes (for the model) the exact value of that shift

Philipp Thomas et Schumann Christoph (sous la direction de, From the Syrian Land to the States of Syria and Lebanon (Beiruter Texte und Studien 96. Würzburg et Beirut: Ergon Verlag in Kommission, 2004, 7 p. + 366 p.

Directory of Open Access Journals (Sweden)

Frank Peter

2007-11-01

Full Text Available Cet ouvrage collectif, dirigé par Thomas Philipp et Christoph Schumann, réunit 21 contributions portant sur l'émergence de nouvelles identités et idéologies, entre les années 1841 et 1940, dans le Bilâd al-Shâm, la région comprise entre les montagnes du Taurus, le désert syrien, le Sinaï et la Méditerranée. Philipp et Schumann considèrent que peu de recherches ont abordé cette région en tant qu’une unité (as integrated region fondée sur des caractéristiques sociales, culturelles et historiqu...

Sound attenuations of axial fan blade tones using flow-driven tunable resonator arrays

Science.gov (United States)

Gorny, Lee James

attained and BPF tones were reduced to less than 5 dB from the broadband noise floor for each case discussed above. In parallel with experimental work, analytical models were developed to effectively model and predict optimal resonator configurations for a given fan in operation. Interactions between resonators and the driving pressure field from the rotor blades are modeled using transmission line (TL) theory. Blade tone acoustic pressure is obtained using a finite element method (FEM) propagation code. By combining of these two methods, a resonator configuration that achieves optimal attenuation can be numerically obtained. The use of resonators has been shown to significantly attenuate fan noise in the conditions explored in the considered experiments. Numerical modeling has shown consistency in the response of flow driven resonators and their. These results indicate a strong potential for active control of fan noise using resonators and an approach to applying this control is presented.

Shape of the Hα emission line in non resonant charge exchange in hydrogen plasmas

International Nuclear Information System (INIS)

Susino Bueno, A.; Zurro Hernandez, B.

1977-01-01

The Hα line shape emitted from a maxwellian hydrogen plasma and produced by non resonant change exchange has been calculated. Its explicit shape depends on the ion temperature, on background neutral energy and on the relative shape of the collision cross section. A comparison between theoretical and experimental shapes of the Hα line is carried out to check the model and to deduce the ion plasma temperature. (author) [es

Critique of atomic physics instability mechanisms: Ionization-driven and radiative microinstabilities in the tokamak edge plasma

International Nuclear Information System (INIS)

Ross, D.W.

1994-01-01

The theory of atomic-process driven microinstabilities in the tokamak edge plasma is reexamined. It is found that these instabilities, as they are usually presented, do not exist. This assertion applies both to ionization-driven modes and to radiative condensation, or thermal-driven modes. The problem is that there exists no separation of time scales between the approach to equilibrium and the growth rate of the purported instabilities. Therefore, to describe the perturbation of an inhomogeneous plasma, it is essential either to establish an equilibrium that includes both perpendicular transport and the proposed source, or, alternatively, to follow the background evolution simultaneously with the growth of the modes. Neither has been done in theoretical or numerical studies of microinstabilities driven by atomic effects in tokamaks. Very near the density limit, macroscopic modes may be unstable, leading to marfes or disruptions, but perturbations of the equilibrium transport fluxes, when taken into account, are sufficient to stabilize the microscopic modes. If the equilibrium fluxes are not included a priori, the ordering breakdown persists into the nonlinear regime. Since the atomic driving terms are the same as in the linear limit, radial decorrelation lengths would have to approach background scale lengths to yield transport of significant magnitude. Under ordinary tokamak conditions, therefore, atomic processes are unlikely to provide an important driving mechanism for the microturbulence that is presumed to cause anomalous transport

Phase-matched third harmonic generation in a plasma

International Nuclear Information System (INIS)

Rax, J.M.; Fisch, N.J.

1993-01-01

Relativistic third harmonic generation in a plasma is investigated. The growth of a third harmonic wave is limited by the difference between the phase velocity of the pump and driven waves. This phase velocity mismatch results in a third harmonic amplitude saturation and oscillation. In order to overcome this saturation, the authors describe a phase-matching scheme based on a resonant density modulation. The limitations of this scheme are analyzed

Role of compressibility on driven magnetic reconnection

International Nuclear Information System (INIS)

Sato, T.; Hayashi, T.; Watanabe, K.; Horiuchi, R.; Tanaka, M.; Sawairi, N.; Kusano, K.

1991-08-01

Whether it is induced by an ideal (current driven) instability or by an external force, plasma flow causes a change in the magnetic field configuration and often gives rise to a current intensification locally, thereby a fast driven reconnection being driven there. Many dramatic phenomena in magnetically confined plasmas such as magnetospheric substorms, solar flares, MHD self-organization and tokamak sawtooth crash, may be attributed to this fast driven reconnection. Using a fourth order MHD simulation code it is confirmed that compressibility of the plasma plays a crucial role in leading to a fast (MHD time scale) driven reconnection. This indicates that the incompressible representation is not always applicable to the study of a global dynamical behavior of a magnetically confined plasma. (author)

Correlation of III/V semiconductor etch results with physical parameters of high-density reactive plasmas excited by electron cyclotron resonance

Science.gov (United States)

Gerhard, FRANZ; Ralf, MEYER; Markus-Christian, AMANN

2017-12-01

Reactive ion etching is the interaction of reactive plasmas with surfaces. To obtain a detailed understanding of this process, significant properties of reactive composite low-pressure plasmas driven by electron cyclotron resonance (ECR) were investigated and compared with the radial uniformity of the etch rate. The determination of the electronic properties of chlorine- and hydrogen-containing plasmas enabled the understanding of the pressure-dependent behavior of the plasma density and provided better insights into the electronic parameters of reactive etch gases. From the electrical evaluation of I(V) characteristics obtained using a Langmuir probe, plasmas of different compositions were investigated. The standard method of Druyvesteyn to derive the electron energy distribution functions by the second derivative of the I(V) characteristics was replaced by a mathematical model which has been evolved to be more robust against noise, mainly, because the first derivative of the I(V) characteristics is used. Special attention was given to the power of the energy dependence in the exponent. In particular, for plasmas that are generated by ECR with EM modes, the existence of Maxwellian distribution functions is not to be taken as a self-evident fact, but the bi-Maxwellian distribution was proven for Ar- and Kr-stabilized plasmas. In addition to the electron temperature, the global uniform discharge model has been shown to be useful for calculating the neutral gas temperature. To what extent the invasive method of using a Langmuir probe could be replaced with the non-invasive optical method of emission spectroscopy, particularly actinometry, was investigated, and the resulting data exhibited the same relative behavior as the Langmuir data. The correlation with etchrate data reveals the large chemical part of the removal process—most striking when the data is compared with etching in pure argon. Although the relative amount of the radial variation of plasma density and

Revisiting linear plasma waves for finite value of the plasma parameter

Science.gov (United States)

Grismayer, Thomas; Fahlen, Jay; Decyk, Viktor; Mori, Warren

2010-11-01

We investigate through theory and PIC simulations the Landau-damping of plasma waves with finite plasma parameter. We concentrate on the linear regime, γφB, where the waves are typically small and below the thermal noise. We simulate these condition using 1,2,3D electrostatic PIC codes (BEPS), noting that modern computers now allow us to simulate cases where (nλD^3 = [1e2;1e6]). We study these waves by using a subtraction technique in which two simulations are carried out. In the first, a small wave is initialized or driven, in the second no wave is excited. The results are subtracted to provide a clean signal that can be studied. As nλD^3 is decreased, the number of resonant electrons can be small for linear waves. We show how the damping changes as a result of having few resonant particles. We also find that for small nλD^3 fluctuations can cause the electrons to undergo collisions that eventually destroy the initial wave. A quantity of interest is the the life time of a particular mode which depends on the plasma parameter and the wave number. The life time is estimated and then compared with the numerical results. A surprising result is that even for large values of nλD^3 some non-Vlasov discreteness effects appear to be important.

Resonant photopumping of a neon lasant plasma by a sodium pump plasma

International Nuclear Information System (INIS)

Young, F.C.; Apruzese, J.P.; Burkhalter, P.G.; Cooperstein, G.; Davis, J.; Mosher, D.; Ottinger, P.F.; Scherrer, V.E.; Stephanakis, S.J.; Mehlman, C.; Welch, B.L.

1988-01-01

Resonant photopumping of heliumlike neon by helium like sodium is being investigated to extend this pumping technique to the soft x-ray region. In the Na-pump/Ne-lasant system, the 1s 2 -1s2p 1 P 1 line of Na X at 11.0027 A differs by 2 parts in 10 4 from the 1s 2 -1s 4 p 1 P 1 line of Ne 1X at 11.0003 A. This wavelength difference corresponds to about one Doppler width at the sodium plasma temperatures (200-500 eV) required for strong Na X pump radiation. Sodium line radiation of sufficient power irradiating a properly prepared neon plasma will cause overpopulation of the Ne 1X n = 4 singlet level leading to lasing in the 4-3, 4-2, and possibly 3-2 singlet transitions. Experimentally, the current pulse from the NRL Gamble-II generator is used to produce side-by-side z-pinch plasmas of sodium fluoride (NaF) and neon. The discharges are viewed radially with x-ray diagnostics including time-integrated pinhole cameras, time-resolved x-ray diodes, and a time-integrated curved-crystal spectrograph. Measurements of the neon plasma indicate that a discharge current of about 200 kA is required to produce a neon lasant with a dominant heliumlike ground-state population. For fluorescence experiments, appropriate neon lasant conditions (density of about 10 18 cm -3 and temperature of 50-100 eV) must be produced at the time of the intense sodium pump-line radiation. Fluorescence is demonstrated by observing enhancement of the 4-1 line (He-γ) from the neon plasma relative to the 3-1 line (He-γ) when the neon is pumped by sodium. An increase in this γ-to-β ratio of 25% has been observed when the sodium pump radiation is present. The results of recent experiments are reported, and their implications for future experiments are discussed

Studies of electron cyclotron resonance ion source plasma physics

International Nuclear Information System (INIS)

Tarvainen, O.

2005-01-01

This thesis consists of an introduction to the plasma physics of electron cyclotron resonance ion sources (ECRIS) and a review of the results obtained by the author and co-workers including discussion of related work by others. The thesis begins with a theoretical discussion dealing with plasma physics relevant for the production of highly charged ions in ECR ion source plasmas. This is followed by an overview of different techniques, such as gas mixing and double frequency heating, that can be used to improve the performance of this type of ion source. The experimental part of the work consists of studies related to ECRIS plasma physics. The effect of the gas mixing technique on the production efficiency of different ion beams was studied with both gaseous and solid materials. It was observed that gas mixing improves the confinement of the heavier element while the confinement of the lighter element is reduced. When the effect of gas mixing on MIVOC-plasmas was studied with several mixing gases it was observed that applying this technique can reduce the inevitable carbon contamination by a significant factor. In order to understand the different plasma processes taking place in ECRIS plasmas, a series of plasma potential and emittance measurements was carried out. An instrument, which can be used to measure the plasma potential in a single measurement without disturbing the plasma, was developed for this work. Studying the plasma potential of ECR ion sources is important not only because it helps to understand different plasma processes, but also because the information can be used as an input parameter for beam transport simulations and ion source extraction design. The experiments performed have revealed clear dependencies of the plasma potential on certain source parameters such as the amount of carbon contamination accumulated on the walls of the plasma chamber during a MIVOC-run. It was also observed that gas mixing affects not only the production efficiency

High energy radiation precursors to the collapse of black holes binaries based on resonating plasma modes

Science.gov (United States)

Coppi, B.

2018-05-01

The presence of well organized plasma structures around binary systems of collapsed objects [1,2] (black holes and neutron stars) is proposed in which processes can develop [3] leading to high energy electromagnetic radiation emission immediately before the binary collapse. The formulated theoretical model supporting this argument shows that resonating plasma collective modes can be excited in the relevant magnetized plasma structure. Accordingly, the collapse of the binary approaches, with the loss of angular momentum by emission of gravitational waves [2], the resonance conditions with vertically standing plasma density and magnetic field oscillations are met. Then, secondary plasma modes propagating along the magnetic field are envisioned to be sustained with mode-particle interactions producing the particle populations responsible for the observable electromagnetic radiation emission. Weak evidence for a precursor to the binary collapse reported in Ref. [2], has been offered by the Agile X-γ-ray observatory [4] while the August 17 (2017) event, identified first by the LIGO-Virgo detection of gravitational waves and featuring the inferred collapse of a neutron star binary, improves the evidence of such a precursor. A new set of experimental observations is needed to reassess the presented theory.

DC-driven plasma gun: self-oscillatory operation mode of atmospheric-pressure helium plasma jet comprised of repetitive streamer breakdowns

Science.gov (United States)

Wang, Xingxing; Shashurin, Alexey

2017-02-01

This paper presents and studies helium atmospheric pressure plasma jet comprised of a series of repetitive streamer breakdowns, which is driven by pure DC high voltage (self-oscillatory behavior). The repetition frequency of the breakdowns is governed by the geometry of discharge electrodes/surroundings and gas flow rate. Each next streamer is initiated when the electric field on the anode tip recovers after the previous breakdown and reaches the breakdown threshold value of about 2.5 kV cm-1. One type of the helium plasma gun designed using this operational principle is demonstrated. The gun operates on about 3 kV DC high voltage and is comprised of the series of the repetitive streamer breakdowns at a frequency of about 13 kHz.

Study of a continuous plasma generated by electron bombardment and its mixing with a laser induced plasma. Influence of collisions on resonance cone phenomenon

International Nuclear Information System (INIS)

Besuelle, E.

1997-01-01

This thesis deals with three different fields of plasma physics. In the first part, we studied free expansion of an ionised uranium vapour generated in an electron beam evaporator. The electron temperature and the electron density of the expanding plasma have been measured by a Langmuir probe. The experimental results have been compared with the ones obtained by numerical simulation using a fluid code. The calculated points are in the error bars. We observe that there are two electron populations with different temperatures, which undergo a mixing during the plasma expansion. The neutral density influence on the electron temperature by collisional relaxation is also studied. The second part deals with a plasma diagnostic which can replace Langmuir probe in the case of a cold magnetized plasma: the resonance cone phenomenon. After recalling the wave propagation theory in a cold plasma, we introduce a new calculation of the potential radiated by an antenna in a collisional magnetized plasma. The domain where the resonance cone exists in considerably reduced because of collisions. More of that, the cone angle is reduced by this phenomenon too. The experiments performed show that we must take into account a wave turbulence phenomenon to explain the High collision frequency that we observe. The third part is about the study of the expansion of a plasma into another one. We solve this problem with fluid codes and Particle-In-Cell (PIC) code. THe electron families have a counter stream motion locally. Then, we study the electrostatic extraction of two plasmas-one pulsed, one continuous-in which we observe electron unfurling. (author)

Quantitative detection of plasma-generated radicals in liquids by electron paramagnetic resonance spectroscopy

International Nuclear Information System (INIS)

Tresp, H; Hammer, M U; Winter, J; Reuter, S; Weltmann, K-D

2013-01-01

In this paper the qualitative and quantitative detection of oxygen radicals in liquids after plasma treatment with an atmospheric pressure argon plasma jet by electron paramagnetic resonance spectroscopy is investigated. Absolute values for · OH and O 2 ·- radical concentration and their net production rate in plasma-treated liquids are determined without the use of additional scavenging chemicals such as superoxide dismutase (SOD) or mannitol (D-MAN). The main oxygen-centred radical generation in PBS was found to originate from the superoxide radical. It is shown that hidden parameters such as the manufacturer of chemical components could have a big influence on the comparability and reproducibility of the results. Finally, the effect of a shielding gas device for the investigated plasma jet with a shielding gas composition of varying oxygen-to-nitrogen ratio on radical generation after plasma treatment of phosphate-buffered saline solution was investigated. (paper)

Time-resolved spectroscopy of plasma resonances in highly excited silicon and germanium

International Nuclear Information System (INIS)

Huang, C.Y.; Malvezzi, A.M.; Bloembergen, N.; Kurz, H.

1985-01-01

The dynamics of the electron-hole plasma in silicon and germanium samples irradiated by 20 ps. 532 nm laser pulses has been investigated in the near infrared by the time-resolved picosecond optical spectroscopy. The experimental reflectivities and transmission are compared with the predictions of the thermal model for degenerate carrier distributions through the Drude formalism. Above a certain fluence, a significant deviation between measured and calculated values indicates a strong increase of the recombination rate as soon as the plasma resonances become comparable with the band gaps. These new plasmon-aided recombination channels are particularly pronounced in germanium. 15 refs., 8 figs

Diagnostic studies of ac-driven plasmas in saline solutions: the effect of frequency on the plasma behavior

International Nuclear Information System (INIS)

Chang, Hung-wen; Hsu, Cheng-che

2011-01-01

The effect of frequency on the characteristics of plasmas in saline solution driven by 50-1000 Hz ac power is studied. Two distinct modes, namely bubble and jetting modes, are identified. The bubble mode occurs under low frequencies. In this mode, a millimeter-sized bubble is tightly attached to the electrode tip and oscillates with the applied voltage. With an increase in frequency, it shows the jetting mode, in which bubbles, hundreds of micometers in diameter, are continuously formed and jetted away from the electrode surface. Such a significant change in the bubble behavior influences the power input at a given applied voltage and significantly affects the plasma behavior. In spite of the fact that no significant difference is seen in the optical emission spectra, the broadening of the H β peak shows that the bubble mode has a lower electron density than that of the jetting mode. The temporally resolved optical emission intensities show light emission in the negative half of the power period regardless of the modes. This shows clearly that the driving frequency significantly influences the bubble dynamics, which in turn alters the plasma behavior.

First plasma of the A-PHOENIX electron cyclotron resonance ion source

International Nuclear Information System (INIS)

Thuillier, T.; Lamy, T.; Latrasse, L.; Angot, J.

2008-01-01

A-PHOENIX is a new compact hybrid electron cyclotron resonance ion source using a large permanent magnet hexapole (1.92 T at the magnet surface) and high temperature superconducting Solenoids (3 T) to make min-vertical bar B vertical bar structure suitable for 28 GHz cw operation. The final assembly of the source was achieved at the end of June 2007. The first plasma of A-PHOENIX at 18 GHz was done on the 16th of August, 2007. The technological specificities of A-PHOENIX are presented. The large hexapole built is presented and experimental magnetic measurements show that it is nominal with respect to simulation. A fake plasma chamber prototype including thin iron inserts showed that the predicted radial magnetic confinement can be fulfilled up to 2.15 T at the plasma chamber wall. Scheduled planning of experiments until the end of 2008 is presented

Quasi-monoenergetic ion beam acceleration by laser-driven shock and solitary waves in near-critical plasmas

International Nuclear Information System (INIS)

Zhang, W. L.; Qiao, B.; Huang, T. W.; Shen, X. F.; You, W. Y.; Yan, X. Q.; Wu, S. Z.; Zhou, C. T.; He, X. T.

2016-01-01

Ion acceleration in near-critical plasmas driven by intense laser pulses is investigated theoretically and numerically. A theoretical model has been given for clarification of the ion acceleration dynamics in relation to different laser and target parameters. Two distinct regimes have been identified, where ions are accelerated by, respectively, the laser-induced shock wave in the weakly driven regime (comparatively low laser intensity) and the nonlinear solitary wave in the strongly driven regime (comparatively high laser intensity). Two-dimensional particle-in-cell simulations show that quasi-monoenergetic proton beams with a peak energy of 94.6 MeV and an energy spread 15.8% are obtained by intense laser pulses at intensity I_0 = 3 × 10"2"0" W/cm"2 and pulse duration τ = 0.5 ps in the strongly driven regime, which is more advantageous than that got in the weakly driven regime. In addition, 233 MeV proton beams with narrow spread can be produced by extending τ to 1.0 ps in the strongly driven regime.

Quasi-monoenergetic ion beam acceleration by laser-driven shock and solitary waves in near-critical plasmas

Energy Technology Data Exchange (ETDEWEB)

Zhang, W. L.; Qiao, B., E-mail: bqiao@pku.edu.cn; Huang, T. W.; Shen, X. F.; You, W. Y. [Center for Applied Physics and Technology, HEDPS, and State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006 (China); Yan, X. Q. [Center for Applied Physics and Technology, HEDPS, and State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Wu, S. Z. [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Zhou, C. T.; He, X. T. [Center for Applied Physics and Technology, HEDPS, and State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China)

2016-07-15

Ion acceleration in near-critical plasmas driven by intense laser pulses is investigated theoretically and numerically. A theoretical model has been given for clarification of the ion acceleration dynamics in relation to different laser and target parameters. Two distinct regimes have been identified, where ions are accelerated by, respectively, the laser-induced shock wave in the weakly driven regime (comparatively low laser intensity) and the nonlinear solitary wave in the strongly driven regime (comparatively high laser intensity). Two-dimensional particle-in-cell simulations show that quasi-monoenergetic proton beams with a peak energy of 94.6 MeV and an energy spread 15.8% are obtained by intense laser pulses at intensity I{sub 0} = 3 × 10{sup 20 }W/cm{sup 2} and pulse duration τ = 0.5 ps in the strongly driven regime, which is more advantageous than that got in the weakly driven regime. In addition, 233 MeV proton beams with narrow spread can be produced by extending τ to 1.0 ps in the strongly driven regime.

Non-Inductively Driven Tokamak Plasmas at Near-Unity Toroidal Beta in the Pegasus Toroidal Experiment

Science.gov (United States)

Reusch, Joshua

2017-10-01

A major goal of the spherical tokamak research program is accessing a state of low internal inductance li, high elongation κ, high toroidal and normalized beta (βt and βN) , and low collisionality without solenoidal current drive. A new local helicity injection (LHI) system in the lower divertor region of the ultra-low aspect ratio Pegasus ST provides non-solenoidally driven plasmas that exhibit most of these characteristics. LHI utilizes compact, edge-localized current sources (Ainj 4 cm2, Iinj 8 kA, Vinj 1.5 kV) for plasma startup and sustainment, and can sustain more than 200 kA of plasma current. Plasma growth via LHI is enhanced by a transition from a regime of high kink-like MHD activity to one of reduced MHD activity at higher frequencies and presumably shorter wavelengths. The strong edge current drive provided by LHI results in a hollow current density profile with low li. The low aspect ratio (R0 / a 1.2) of Pegasus allows ready access to high κ and MHD stable operation at very high normalized plasma currents (IN =Ip /aBT> 15). Thomson scattering measurements indicate Te 100 eV and ne 1 ×19 m-3. The impurity Ti evolution is correlated in time with high frequency magnetic fluctuations, implying substantial reconnection ion heating is driven by the applied helicity injection. Doppler spectroscopy indicates Ti >=Te and that the anomalous ion heating scales consistently with two fluid reconnection theory. Taken together, these features provide access to very high βt plasmas. Equilibrium analyses indicate βt up to 100% and βN 6.5 is achieved. At increasingly low BT, the discharge disrupts at the no-wall ideal stability limit. In these high βt discharges, a minimum |B| well forms over 50% of the plasma volume. This unique magnetic configuration may be of interest for testing predictions of stabilizing drift wave turbulence and/or improving energetic particle confinement. This work supported by US DOE Grants DE-FG02-96ER54375 and DE-SC0006928.

Control of plasma density distribution via wireless power transfer in an inductively coupled plasma

International Nuclear Information System (INIS)

Lee, Hee-Jin; Lee, Hyo-Chang; Kim, Young-Cheol; Chung, Chin-Wook

2013-01-01

With an enlargement of the wafer size, development of large-area plasma sources and control of plasma density distribution are required. To control the spatial distribution of the plasma density, wireless power transfer is applied to an inductively coupled plasma for the first time. An inner powered antenna and an outer resonant coil connected to a variable capacitor are placed on the top of the chamber. As the self-resonance frequency ω r of the resonant coil is adjusted, the power transfer rate from the inner powered coil to the outer resonant coil is changed and the dramatic evolution of the plasma density profile is measured. As ω r of the outer resonant coil changes from the non-resonant condition (where ω r is not the driving angular frequency ω rf ) to the resonant condition (where ω r = ω rf ), the plasma density profile evolves from a convex shape with maximal plasma density at the radial center into a concave shape with maximal plasma density in the vicinity of the resonant antenna coil. This result shows that the plasma density distribution can be successfully controlled via wireless resonance power transfer. (fast track communication)

Theory and observation of compressional Alfven eigenmodes in low aspect ratio plasma

International Nuclear Information System (INIS)

Gorelenkov, N.N.

2002-01-01

A new theory of radially and poloidally localized Compressional Alfven Eigenmodes (CAE) in low aspect ratio plasma is reported. The theory is applied to identify recently observed instabilities in the MHz frequency range in National Spherical Torus experiments (NSTX). The frequency of observed CAEs is correlated with the characteristic Alfven velocity of the plasma. The observed high frequency modes are explained as CAEs driven by energetic beam ions. The CAE frequency is determined by the Alfven frequency at the mode location on the low field side of the plasma and is given approximately by ω CAE v A m=r, where m is the poloidal mode number, and r is the local minor radius. CAEs are destabilized by free energy in the energetic ion velocity space gradient via Doppler shifted cyclotron resonance with beam ions. Properties of the CAE instability driven by different NBI ion distributions are presented. (author)

Anisotropy effects on curvature-driven flute instabilities in a hot-electron plasma

International Nuclear Information System (INIS)

Spong, D.A.; Berk, H.L.; Van Dam, J.W.; Rosenbluth, M.N.

1982-08-01

The effects of finite parallel temperature are investigated for a hot electron plasma with sufficiently large beta that the magnetic field scale length (Δ/sub B/) is small compared with the vacuum field radius of curvature (R). Numerical and analytical estimates of stability boundaries are obtained for the four possible modes that can be treated in this limit: the conventional hot electron interchange, the high frequency hot electron interchange (ω > ω/sub ci/), the compressional Alfven mode, and the interacting pressure-driven interchange

Model of a source-driven plasma interacting with a wall in an oblique magnetic field

International Nuclear Information System (INIS)

Ahedo, E.; Carralero, D.

2009-01-01

A fluid model of a magnetized source-driven plasma is discussed for regimes with (Debye length)<<(ion Larmor radius)<<(plasma size and collisional mean-free path). Plasma collection by the wall is determined in terms of angle of incidence, magnetic strength, and plasma collisionality. For nonparallel incidence, a three-scale asymptotic analysis reveals a three-region matched structure consisting of a magnetically aligned bulk region, the Chodura layer, and the Debye sheath. Sonic Chodura and Bohm conditions define the singular region transitions. For near-parallel incidence, a separate analysis demonstrates the presence of a diffusive-collisional bulk region followed by a thin collisionless layer, which differs partially from the Chodura layer. A parametric analysis unveils the presence of four regimes depending on plasma collisionality: (1) a collisionless regime, with the magnetically channeled bulk region governed by plasma production; (2) a resistive semicollisional regime, where collisions retard the plasma transport in the bulk region; (3) a diffusive semicollisional regime, where the ExB drift dominates the ion flux in the bulk region; and (4) a collisional regime, where collisions cancel out magnetic effects. At grazing incidence, plasma collection is found to vary nonmonotonically with plasma collisionality. Nonzero Debye-length effects are discussed briefly.

Study of a continuous plasma generated by electron bombardment and its mixing with a laser induced plasma. Influence of collisions on resonance cone phenomenon; Contribution a l`etude d`un plasma cree de facon continue par bombardement electronique et de son melange avec un photo-plasma pulse. Influence des collisions sur les cones de resonance

Energy Technology Data Exchange (ETDEWEB)

Besuelle, E.

1997-02-25

This thesis deals with three different fields of plasma physics. In the first part, we studied free expansion of an ionised uranium vapour generated in an electron beam evaporator. The electron temperature and the electron density of the expanding plasma have been measured by a Langmuir probe. The experimental results have been compared with the ones obtained by numerical simulation using a fluid code. The calculated points are in the error bars. We observe that there are two electron populations with different temperatures, which undergo a mixing during the plasma expansion. The neutral density influence on the electron temperature by collisional relaxation is also studied. The second part deals with a plasma diagnostic which can replace Langmuir probe in the case of a cold magnetized plasma: the resonance cone phenomenon. After recalling the wave propagation theory in a cold plasma, we introduce a new calculation of the potential radiated by an antenna in a collisional magnetized plasma. The domain where the resonance cone exists in considerably reduced because of collisions. More of that, the cone angle is reduced by this phenomenon too. The experiments performed show that we must take into account a wave turbulence phenomenon to explain the High collision frequency that we observe. The third part is about the study of the expansion of a plasma into another one. We solve this problem with fluid codes and Particle-In-Cell (PIC) code. THe electron families have a counter stream motion locally. Then, we study the electrostatic extraction of two plasmas-one pulsed, one continuous-in which we observe electron unfurling. (author).

Resonant third-harmonic generation of a short-pulse laser from electron-hole plasmas

Energy Technology Data Exchange (ETDEWEB)

Kant, Niti [Department of Physics, Lovely Professional University, Phagwara, Punjab 144 402 (India); Nandan Gupta, Devki [Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India); Suk, Hyyong [Advanced Photonics Research Institute (APRI) and Graduate Program of Photonics and Applied Physics, Gwangju Institute of Science and Technology, Gwangju 500 712 (Korea, Republic of)

2012-01-15

In semiconductors, free carriers are created in pairs in inter-band transitions and consist of an electron and its corresponding hole. At very high carrier densities, carrier-carrier collisions dominate over carrier-lattice collisions and carriers begin to behave collectively to form plasma. Here, we apply a short-pulse laser to generate third-harmonic radiation from a semiconductor plasma (electron-hole plasma) in the presence of a transverse wiggler magnetic-field. The process of third-harmonic generation of an intense short-pulse laser is resonantly enhanced by the magnetic wiggler, i.e., wiggler magnetic field provides the necessary momentum to third-harmonic photons. In addition, a high-power laser radiation, propagating through a semiconductor imparts an oscillatory velocity to the electrons and exerts a ponderomotive force on electrons at the third-harmonic frequency of the laser. This oscillatory velocity produces a third-harmonic longitudinal current. And due to the beating of the longitudinal electron velocity and the wiggler magnetic field, a transverse third-harmonic current is produced that drives third-harmonic electromagnetic radiation. It is finally observed that for a specific wiggler wave number value, the phase-matching conditions for the process are satisfied, leading to resonant enhancement in the energy conversion efficiency.

Resonant third-harmonic generation of a short-pulse laser from electron-hole plasmas

International Nuclear Information System (INIS)

Kant, Niti; Nandan Gupta, Devki; Suk, Hyyong

2012-01-01

In semiconductors, free carriers are created in pairs in inter-band transitions and consist of an electron and its corresponding hole. At very high carrier densities, carrier-carrier collisions dominate over carrier-lattice collisions and carriers begin to behave collectively to form plasma. Here, we apply a short-pulse laser to generate third-harmonic radiation from a semiconductor plasma (electron-hole plasma) in the presence of a transverse wiggler magnetic-field. The process of third-harmonic generation of an intense short-pulse laser is resonantly enhanced by the magnetic wiggler, i.e., wiggler magnetic field provides the necessary momentum to third-harmonic photons. In addition, a high-power laser radiation, propagating through a semiconductor imparts an oscillatory velocity to the electrons and exerts a ponderomotive force on electrons at the third-harmonic frequency of the laser. This oscillatory velocity produces a third-harmonic longitudinal current. And due to the beating of the longitudinal electron velocity and the wiggler magnetic field, a transverse third-harmonic current is produced that drives third-harmonic electromagnetic radiation. It is finally observed that for a specific wiggler wave number value, the phase-matching conditions for the process are satisfied, leading to resonant enhancement in the energy conversion efficiency.

Design of a free-electron laser driven by the LBNL laser-plasma-accelerator

International Nuclear Information System (INIS)

Schroeder, C.B.; Fawley, W.M.; Montgomery, A.L.; Robinson, K.E.; Gruner, F.; Bakeman, M.; Leemans, W.P.

2007-01-01

We discuss the design and current status of a compact free-electron laser (FEL), generating ultra-fast, high-peak flux, VUV pulses driven by a high-current, GeV electron beam from the existing Lawrence Berkeley National Laboratory (LBNL) laser-plasma accelerator, whose active acceleration length is only a few cm. The proposed ultra-fast source would be intrinsically temporally synchronized to the drive laser pulse, enabling pump-probe studies in ultra-fast science with pulse lengths of tens of fs. Owing to the high current ( and 10 kA) of the laser-plasma-accelerated electron beams, saturated output fluxes are potentially greater than 1013 photons/pulse. Devices based both on SASE and high-harmonic generated input seeds, to reduce undulator length and fluctuations, are considered

Influence of the shear flow on electron cyclotron resonance plasma confinement in an axisymmetric magnetic mirror trap of the electron cyclotron resonance ion source.

Science.gov (United States)

Izotov, I V; Razin, S V; Sidorov, A V; Skalyga, V A; Zorin, V G; Bagryansky, P A; Beklemishev, A D; Prikhodko, V V

2012-02-01

Influence of shear flows of the dense plasma created under conditions of the electron cyclotron resonance (ECR) gas breakdown on the plasma confinement in the axisymmetric mirror trap ("vortex" confinement) was studied experimentally and theoretically. A limiter with bias potential was set inside the mirror trap for plasma rotation. The limiter construction and the optimal value of the potential were chosen according to the results of the preliminary theoretical analysis. This method of "vortex" confinement realization in an axisymmetric mirror trap for non-equilibrium heavy-ion plasmas seems to be promising for creation of ECR multicharged ion sources with high magnetic fields, more than 1 T.

Influence of the shear flow on electron cyclotron resonance plasma confinement in an axisymmetric magnetic mirror trap of the electron cyclotron resonance ion source

International Nuclear Information System (INIS)

Izotov, I. V.; Razin, S. V.; Sidorov, A. V.; Skalyga, V. A.; Zorin, V. G.; Bagryansky, P. A.; Beklemishev, A. D.; Prikhodko, V. V.

2012-01-01

Influence of shear flows of the dense plasma created under conditions of the electron cyclotron resonance (ECR) gas breakdown on the plasma confinement in the axisymmetric mirror trap (''vortex'' confinement) was studied experimentally and theoretically. A limiter with bias potential was set inside the mirror trap for plasma rotation. The limiter construction and the optimal value of the potential were chosen according to the results of the preliminary theoretical analysis. This method of ''vortex'' confinement realization in an axisymmetric mirror trap for non-equilibrium heavy-ion plasmas seems to be promising for creation of ECR multicharged ion sources with high magnetic fields, more than 1 T.

Broadband frequency ECR ion source concepts with large resonant plasma volumes

International Nuclear Information System (INIS)

Alton, G.D.

1995-01-01

New techniques are proposed for enhancing the performances of ECR ion sources. The techniques are based on the use of high-power, variable-frequency, multiple-discrete-frequency, or broadband microwave radiation, derived from standard TWT technology, to effect large resonant ''volume'' ECR sources. The creation of a large ECR plasma ''volume'' permits coupling of more power into the plasma, resulting in the heating of a much larger electron population to higher energies, the effect of which is to produce higher charge state distributions and much higher intensities within a particular charge state than possible in present forms of the ECR ion source. If successful, these developments could significantly impact future accelerator designs and accelerator-based, heavy-ion-research programs by providing multiply-charged ion beams with the energies and intensities required for nuclear physics research from existing ECR ion sources. The methods described in this article can be used to retrofit any ECR ion source predicated on B-minimum plasma confinement techniques

Propagation Dynamics Associated with Resonant Magnetic Perturbation Fields in High-Confinement Mode Plasmas inside the KSTAR Tokamak.

Science.gov (United States)

Xiao, W W; Evans, T E; Tynan, G R; Yoon, S W; Jeon, Y M; Ko, W H; Nam, Y U; Oh, Y K

2017-11-17

The propagation dynamics of resonant magnetic perturbation fields in KSTAR H-mode plasmas with injection of small edge perturbations produced by a supersonic molecular beam injection is reported for the first time. The results show that the perturbation field first excites a plasma response on the q=3 magnetic surface and then propagates inward to the q=2 surface with a radially averaged propagation velocity of resonant magnetic perturbations field equal to 32.5  m/ s. As a result, the perturbation field brakes the toroidal rotation on the q=3 surface first causing a momentum transport perturbation that propagates both inward and outward. A higher density fluctuation level is observed. The propagation velocity of the resonant magnetic perturbations field is larger than the radial propagation velocity of the perturbation in the toroidal rotation.

Experimental evidence of E × B plasma rotation in a 2.45 GHz hydrogen discharge

Energy Technology Data Exchange (ETDEWEB)

Cortázar, O. D., E-mail: daniel.cortazar@uclm.es [Institute for Energy Research-INEI, University of Castilla-La Mancha, C.J. Cela s/n, 13170 Ciudad Real (Spain); Megía-Macías, A. [CERN, BE-ABP-HSL Department, CH1211 Geneva (Switzerland); E.S.S. Bilbao, Polígono Ugaldeguren III, A-7B, 48170 Zamudio (Spain); Tarvainen, O.; Koivisto, H. [Department of Physics, Accelerator Laboratory, University of Jyväskylä, PO Box 35 (YFL), 40500 Jyväskylä (Finland)

2015-12-15

An experimental observation of a rotating plasma structure in a 2.45 GHz microwave-driven hydrogen discharge is reported. The rotation is presumably produced by E × B drift. The formation of the rotating plasma structure is sensitive to the strength of the off-resonance static magnetic field. The rotation frequency is on the order of 10 kHz and is affected by the neutral gas pressure and applied microwave power.

Experimental evidence of E × B plasma rotation in a 2.45 GHz hydrogen discharge

International Nuclear Information System (INIS)

Cortázar, O. D.; Megía-Macías, A.; Tarvainen, O.; Koivisto, H.

2015-01-01

An experimental observation of a rotating plasma structure in a 2.45 GHz microwave-driven hydrogen discharge is reported. The rotation is presumably produced by E × B drift. The formation of the rotating plasma structure is sensitive to the strength of the off-resonance static magnetic field. The rotation frequency is on the order of 10 kHz and is affected by the neutral gas pressure and applied microwave power

Nonlinear Electromagnetic Stabilization of Plasma Microturbulence

Science.gov (United States)

Whelan, G. G.; Pueschel, M. J.; Terry, P. W.

2018-04-01

The physical causes for the strong stabilizing effect of finite plasma β on ion-temperature-gradient-driven turbulence, which far exceeds quasilinear estimates, are identified from nonlinear gyrokinetic simulations. The primary contribution stems from a resonance of frequencies in the dominant nonlinear interaction between the unstable mode, the stable mode, and zonal flows, which maximizes the triplet correlation time and therefore the energy transfer efficiency. A modification to mixing-length transport estimates is constructed, which reproduces nonlinear heat fluxes throughout the examined β range.

Electron plasma waves in CO/sub 2/ laser plasma interactions

International Nuclear Information System (INIS)

Baldis, H.A.; Villeneuve, D.M.; Walsh, C.J.

1984-01-01

During the past few years, the use of Thomson scattering in CO/sub 2/ laser produced plasmas has permitted the identification and study of electron plasma waves and ion waves, driven by various instabilities in the plasma corona, such as Stimulated Raman Scattering (SRS), two plasmon decay, and Stimulated Brillouin Scattering (SBS). Since these instabilities may coexist in the plasma, the density fluctuations associated with one wave may influence the behaviour of one or more of the other instabilities. The authors discuss the experimental evidence of such effects and, in particular, the consequences of a recent experiment in which the ion waves driven by SBS were observed to adversely affect the production of the electron plasma waves driven by SRS. In that experiment, a strong correlation was observed between the onset of SBS and the disappearance of the electron plasma waves driven by SRS at low densities (n/sub e/ n/sub e/ > 0.05 n/sub c/)

Proton radiography of petawatt-driven channel formation in a plasma gradient

Science.gov (United States)

Hill, Matthew; Sircombe, Nathan; Ramsay, Martin; Brown, Colin; Hobbs, Lauren; Allan, Peter; James, Steven; Norreys, Peter; Ratan, Naren; Ceurvorst, Luke

2015-11-01

Channel formation by ultra-intense laser pulses in underdense plasmas is a challenging simulation problem with direct relevance to many areas of current research. Recent experiments at the Orion laser facility have used high-energy proton radiography (>40 MeV) driven by a 1 ω petawatt beam to directly probe the interaction of another petawatt beam with a well-characterized plasma density gradient. The interaction plasma was generated using a 3 ω long-pulse beam and diagnosed using a 2 ω optical probe, simultaneously imaged onto four gated optical imagers and two streak cameras. The unique capabilities of the Orion facility allowed a comparison of the channels generated by intense 1 ω (1 μm, 100-500 J, 0.6 ps, 1021 W/cm2, f/3 parabola) and 2 ω (0.5 μm, 100 J, 0.6 ps, 1020 W/cm2, f/6 parabola) pulses. Proton radiographs of these channels are presented along with PIC simulations performed using the EPOCH code, supported by K- α measurements of hot electron beam divergence and magnetic spectrometer data. Together these provide a solid foundation for improvements to hydrodynamic and PIC simulations, further developing the predictive capabilities required to optimize future experiments.

Design optimization and fatigue testing of an electronically-driven mechanically-resonant cantilever spring mechanism

International Nuclear Information System (INIS)

Kheng, Lim Boon; Kean, Koay Loke; Gitano-Briggs, Horizon

2010-01-01

A light scanning device consisting of an electronically-driven mechanically-resonant cantilever spring-mirror system has been developed for innovative lighting applications. The repeated flexing of the cantilever spring during operation can lead to premature fatigue failure. A model was created to optimize the spring design. The optimized spring design can reduce stress by approximately one-third from the initial design. Fatigue testing showed that the optimized spring design can operate continuously for over 1 month without failure. Analysis of failures indicates surface cracks near the root of the spring are responsible for the failures.

Effect of Ambipolar Plasma Flow on the Penetration of Resonant Magnetic Perturbations in a Quasi-axisymmetric Stellarator

International Nuclear Information System (INIS)

Reiman, A.; Zarnstorff, M.; Mikkelsen, D.; Owen, L.; Mynick, H.; Hudson, S.; Monticello, D.

2005-01-01

A reference equilibrium for the U.S. National Compact Stellarator Experiment is predicted to be sufficiently close to quasi-symmetry to allow the plasma to flow in the toroidal direction with little viscous damping, yet to have sufficiently large deviations from quasi-symmetry that nonambipolarity significantly affects the physics of the shielding of resonant magnetic perturbations by plasma flow. The unperturbed velocity profile is modified by the presence of an ambipolar potential, which produces a broad velocity profile. In the presence of a resonant magnetic field perturbation, nonambipolar transport produces a radial current, and the resulting j x B force resists departures from the ambipolar velocity and enhances the shielding

Temperature anisotropy in a cyclotron resonance heated tokamak plasma and the generation of poloidal electric field

International Nuclear Information System (INIS)

Choe, W.; Ono, M.; Chang, C.S.

1994-11-01

The temperature anisotropy generated by cyclotron resonance heating of tokamak plasmas is calculated and the poloidal equilibrium electric field due to the anisotropy is studied. For the calculation of anisotropic temperatures, bounce-averaged Fokker-Planck equation with a bi-Maxwellian distribution function of heated particles is solved, assuming a moderate wave power and a constant quasilinear cyclotron resonance diffusion coefficient. The poloidal electrostatic potential variation is found to be proportional to the particle density and the degree of temperature anisotropy of warm species created by cyclotron resonance heating

Atmospheric pressure plasma jet's characterization and surface wettability driven by neon transformer

Science.gov (United States)

Elfa, R. R.; Nafarizal, N.; Ahmad, M. K.; Sahdan, M. Z.; Soon, C. F.

2017-03-01

Atmospheric pressure plasma driven by Neon transformer power supply argon is presented in this paper. Atmospheric pressure plasma system has attracted researcher interest over low pressure plasma as it provides a flexibility process, cost-efficient, portable device and vacuum-free device. Besides, another golden key of this system is the wide promising application in the field of work cover from industrial and engineering to medical. However, there are still numbers of fundamental investigation that are necessary such as device configuration, gas configuration and its effect. Dielectric barrier discharge which is also known as atmospheric pressure plasma discharge is created when there is gas ionization process occur which enhance the movement of atom and electron and provide energetic particles. These energetic particles can provide modification and cleaning property to the sample surface due to the bombardment of the high reactive ion and radicals to the sample surface. In order to develop atmospheric pressure plasma discharge, a high voltage and high frequency power supply is needed. In this work, we used a neon transformer power supply as the power supply. The flow of the Ar is feed into 10 mm cylinder quartz tube with different treatment time in order to investigate the effect of the plasma discharge. The analysis of each treatment time is presented by optical emission spectroscopy (OES) and water contact angle (WCA) measurement. The increase of gas treatment time shows increases intensity of reactive Ar and reduces the angle of water droplets in water contact angle. Treatment time of 20 s microslide glass surface shows that the plasma needle discharges have modified the sample surface from hydrophilic surface to superhydrophilic surface. Thus, this leads to another interesting application in reducing sample surface adhesion to optimize productivity in the industry of paintings, semiconductor and more.

Development and studies on a compact electron cyclotron resonance plasma source

Science.gov (United States)

Ganguli, A.; Tarey, R. D.; Arora, N.; Narayanan, R.

2016-04-01

It is well known that electron cyclotron resonance (ECR) produced plasmas are efficient, high-density plasma sources and have many industrial applications. The concept of a portable compact ECR plasma source (CEPS) would thus become important from an application point of view. This paper gives details of such a CEPS that is both portable and easily mountable on a chamber of any size. It uses a fully integrated microwave line operating at 2.45 GHz, up to 800 W, cw. The required magnetic field is produced by a set of suitably designed NdFeB ring magnets; the device has an overall length of  ≈60 cm and weighs  ≈14 kg including the permanent magnets. The CEPS was attached to a small experimental chamber to judge its efficacy for plasma production. In the pressure range of 0.5-10 mTorr and microwave power of  ≈400-500 W the experiments indicate that the CEPS is capable of producing high-density plasma (≈9  ×  1011-1012 cm-3) with bulk electron temperature in the range  ≈2-3 eV. In addition, a warm electron population with density and temperature in the range ≈7  ×  108-109 cm-3 and  ≈45-80 eV, respectively has been detected. This warm population plays an important role at high pressures in maintaining the high-density plasma, when plasma flow from the CEPS into the test chamber is strongly affected.

Self-organized Te Redistribution during Driven Reconnection Processes in High Temperature Plasmas

International Nuclear Information System (INIS)

Park, H.K.; Mazzucato, E.; Luhmann, N.C. Jr.; Domier, C.W.; Xia, Z.; Munsat, T.; Donne, A.J.H.; Classen, I.G.J.; van de Pol, M.J.

2005-01-01

Two-dimensional (2-D) images of electron temperature fluctuations with a high temporal and spatial resolution were employed to study the sawtooth oscillation in TEXTOR tokamak plasmas. The new findings are: (1) 2-D images revealed that the reconnection is localized and permitted the determination of the physical dimensions of the reconnection zone in the poloidal and toroidal planes. (2) The combination of a pressure driven mode and a kink instability leads to an 'X-point' reconnection process. (3) Reconnection can take place anywhere along the q∼1 rational magnetic surface (both high and low field sides). (4) Heat flow from the core to the outside of the inversion radius during the reconnection time is highly asymmetric and the behavior is collective. These new findings are compared with the characteristics of various theoretical models and experimental results for the study of the sawtooth oscillation in tokamak plasmas

Non-inductively driven tokamak plasmas at near-unity βt in the Pegasus toroidal experiment

Science.gov (United States)

Reusch, J. A.; Bodner, G. M.; Bongard, M. W.; Burke, M. G.; Fonck, R. J.; Pachicano, J. L.; Perry, J. M.; Pierren, C.; Rhodes, A. T.; Richner, N. J.; Rodriguez Sanchez, C.; Schlossberg, D. J.; Weberski, J. D.

2018-05-01

A major goal of the spherical tokamak (ST) research program is accessing a state of low internal inductance ℓi, high elongation κ, and high toroidal and normalized beta ( βt and βN) without solenoidal current drive. Local helicity injection (LHI) in the Pegasus ST [Garstka et al., Nucl. Fusion 46, S603 (2006)] provides non-solenoidally driven plasmas that exhibit these characteristics. LHI utilizes compact, edge-localized current sources for plasma startup and sustainment. It results in hollow current density profiles with low ℓi. The low aspect ratio ( R0/a ˜1.2 ) of Pegasus allows access to high κ and high normalized plasma currents ( IN=Ip/a BT>14 ). Magnetic reconnection during LHI provides auxiliary ion heating. Together, these features provide access to very high βt plasmas. Equilibrium analyses indicate that βt up to ˜100% is achieved. These high βt discharges disrupt at the ideal no-wall β limit at βN˜7.

Evidence for fast-electron-driven Alfvenic modes in the HSX stellarator

International Nuclear Information System (INIS)

Brower, D.L.; Deng, C.; Spong, D.A.; Abdou, A.; Almagri, A.F.; Anderson, D.T.; Anderson, F.S.B.; Guttenfelder, W.; Likin, K.; Oh, S.; Sakaguchi, V.; Talmadge, J.N.; Zhai, K.

2005-01-01

The helically-symmetric experiment (HSX) stellarator device is the first of a new generation of stellarators that exploit the concept of quasi-symmetric magnetic fields. In HSX, the plasma is both produced and heated by use of electron cyclotron resonance heating (ECRH) at the 2nd harmonic X-mode resonance. This heating configuration generates a nonthermal energetic electron population. Herein, we report on the first experimental evidence for fast-electron-driven Global Alfven Eigenmodes (GAE). This mode has previously been observed in both tokamaks and stellarators but it was always driven by energetic ions, not electrons. Evidence for this instability is obtained from quasi-helically symmetric HSX plasmas. Potential consequences of these measurements are twofold; (1) fast electrons can drive the GAE instability, and (2) quasi-symmetry makes a difference by better confining the particles that drive the instability as compared to the conventional stellarator configuration. We report on several features of this fluctuation. It is a coherent mode that is experimentally observed in the plasma core and edge by external magnetic coils, interferometry, ECE and Langmuir probes diagnostics. Fluctuations are observed in the frequency range of 20-120 kHz and scale with ion mass density according to expectations for Alfvenic modes. The mode is observed to be global with odd poloidal mode number (inferred from interferometry, possibly m=1) and is present in quasi-helically symmetric HSX plasmas. When quasi-helical symmetry is broken, the mode is no longer observed. Theory predicts a GAE mode in the gap below the Alfven continua can be excited in the frequency range of the measured fluctuations. By employing a biased electrode inserted deep into the plasma, flows can be generated. Under these conditions, the Alfvenic mode amplitude can increase and the fluctuation is even observed in the conventional stellarator configuration. Shifts in the measured frequency can be used to

Non-inductively driven currents in JET

International Nuclear Information System (INIS)

Challis, C.D.; Cordey, J.G.; Hamnen, H.; Stubberfield, P.M.; Christiansen, J.P.; Lazzaro, E.; Muir, D.G.; Stork, D.; Thompson, E.

1989-01-01

Neutral beam heating data from JET have been analysed in detail to determine what proportion of the current is driven non-inductively. It is found that in low density limiter discharges, currents of the order of 0.5 MA are driven, while in H-mode plasmas currents of the order of 0.7 MA are measured. These measured currents are found to be in reasonable agreement with theoretical predictions based on neoclassical models. In low density plasmas the beam driven current is large while the neoclassical bootstrap current dominates H-mode plasmas. (author). 19 refs, 11 figs

Plasma rotation effect on interaction of low frequency fields with plasmas at the rational surfaces in tokamaks

International Nuclear Information System (INIS)

Rondan, E.R.; Elfimov, A.G.; Galvao, R.M.O.; Pires, C.J.A.

2006-01-01

The effect of plasma rotation on low frequency (LF) field penetration, absorption and ponderomotive forces in TEXTOR and in Tokamak Chauffage Alfven Bresilien (TCABR) is investigated in the frequency band of 1-10 kHz. The LF fields are driven by the dynamic ergodic divertor in TEXTOR and the ergodic magnetic limiter in TCABR. Alfven wave mode conversion is responsible for the LF field absorption at the rational magnetic surface where q = -M/N is the integer. Analytical and numerical calculations show the maxima of the LF field absorption at the local Alfven wave resonance ω - k · U = k parallel c A , where ω and k are the frequency and the wave vector, respectively, and c A is the Alfven velocity at the rational magnetic surface q = 2, 3 in TEXTOR and TCABR. The rotation velocity U along the magnetic surfaces, taken into account in the dielectric tensor, can strongly modify the LF field and dissipated power profiles. The absorption in the local AW resonances begins to be non-symmetric in relation to the resonance surface. Calculations show that coil impedance has a maximum related to excitation of some stable (possibly Suydam) modes for waves travelling in the direction of plasma rotation

The non-resonant decay of the fast magnetosonic wave during ICRH of a tokamak plasma

International Nuclear Information System (INIS)

Avinash, K.; Core, W.G.; Hellsten, T.; Farrell, C.M.

1988-01-01

The non-resonant decay of the fast magnetosonic wave into an Ion Bernstein wave and a quasi-mode is investigated from the point of view of assessing the importance of this process for the observed direct heating of the edge plasma during ion-cyclotron resonance heating (ICRH). Starting from the Maxwell-Vlasov equations, expressions for the threshold electric field and the growth rates of the decay process are obtained. For JET like parameters, the thresholds for the decay are easily exceeded and the growth time for typical fast wave electric field strengths is of the order of a microsecond. The parametric dependence of the threshold on magnetic field, temperature, the density of the various ion species, and electron-ion collisions is studied. Finally the relevance of this process to the heating of plasma edge during ICRH is discussed. (author)

Two-fluid and nonlinear effects of tearing and pressure-driven resistive modes in reversed field pinches

International Nuclear Information System (INIS)

Mirnov, V.V.

2002-01-01

Large-scale tearing instabilities have long been considered to underlie transport and dynamo processes in the reversed field pinch (RFP). The vast majority of theoretical and computational RFP work has focused on pressureless, single-fluid MHD in cylindrical plasmas driven solely by a toroidal electric field. We report results of five investigations covering two-fluid dynamos, toroidal nonlinear MHD computation, nonlinear computation of Oscillating Field Current Drive (OFCD), the effect of shear flow on tearing instability, and the effect of pressure on resistive instability. The key findings are: (1) two-fluid dynamo arising from the Hall term is much larger than the standard MHD dynamo present in a single-fluid treatment, (2) geometric coupling from toroidicity precludes the occurrence of laminar single helicity states, except for nonreversed plasmas, (3) OFCD, a form of AC helicity injection, can sustain the RFP plasma current, although magnetic fluctuations are enhanced, (4) edge shear flow can destabilize the edge resonant m=0 modes, which occur as spikes in experiment, and (5) pressure driven modes are resistive at low beta, only becoming ideal at extremely high beta. (author)

Global Hybrid Simulations of Energetic Particle-driven Modes in Toroidal Plasmas

International Nuclear Information System (INIS)

Fu, G.Y.; Breslau, J.; Fredrickson, E.; Park, W.; Strauss, H.R.

2004-01-01

Global hybrid simulations of energetic particle-driven MHD modes have been carried out for tokamaks and spherical tokamaks using the hybrid code M3D. The numerical results for the National Spherical Tokamak Experiments (NSTX) show that Toroidal Alfven Eigenmodes are excited by beam ions with their frequencies consistent with the experimental observations. Nonlinear simulations indicate that the n=2 mode frequency chirps down as the mode moves out radially. For ITER, it is shown that the alpha-particle effects are strongly stabilizing for internal kink mode when central safety factor q(0) is sufficiently close to unity. However, the elongation of ITER plasma shape reduces the stabilization significantly

Numerical simulation of plasma response to externally applied resonant magnetic perturbation on the J-TEXT tokamak

Science.gov (United States)

Bicheng, LI; Zhonghe, JIANG; Jian, LV; Xiang, LI; Bo, RAO; Yonghua, DING

2018-05-01

Nonlinear magnetohydrodynamic (MHD) simulations of an equilibrium on the J-TEXT tokamak with applied resonant magnetic perturbations (RMPs) are performed with NIMROD (non-ideal MHD with rotation, open discussion). Numerical simulation of plasma response to RMPs has been developed to investigate magnetic topology, plasma density and rotation profile. The results indicate that the pure applied RMPs can stimulate 2/1 mode as well as 3/1 mode by the toroidal mode coupling, and finally change density profile by particle transport. At the same time, plasma rotation plays an important role during the entire evolution process.

Resonance self-shielding effect analysis of neutron data libraries applied for the dual-cooled waste transmutation blanket of the fusion-driven subcritical system

International Nuclear Information System (INIS)

Liu Haibo; Wu Yican; Zheng Shanliang; Zhang Chunzao

2004-01-01

Based on the Fusion-Driven Subcritical System (FDS-I), the 25 groups, 175 groups and 620 groups neutron nuclear data libraries with/without resonance self-shielding correction are made with the Njoy and Transx codes, and the K eff and reaction rates are calculated with the Anisn code. The conclusion indicates that the resonance self-shielding effect affects the reaction rates strongly. (authors)

Slit shaped microwave induced atmospheric pressure plasma based on a parallel plate transmission line resonator

Science.gov (United States)

Kang, S. K.; Seo, Y. S.; Lee, H. Wk; Aman-ur-Rehman; Kim, G. C.; Lee, J. K.

2011-11-01

A new type of microwave-excited atmospheric pressure plasma source, based on the principle of parallel plate transmission line resonator, is developed for the treatment of large areas in biomedical applications such as skin treatment and wound healing. A stable plasma of 20 mm width is sustained by a small microwave power source operated at a frequency of 700 MHz and a gas flow rate of 0.9 slm. Plasma impedance and plasma density of this plasma source are estimated by fitting the calculated reflection coefficient to the measured one. The estimated plasma impedance shows a decreasing trend while estimated plasma density shows an increasing trend with the increase in the input power. Plasma uniformity is confirmed by temperature and optical emission distribution measurements. Plasma temperature is sustained at less than 40 °C and abundant amounts of reactive species, which are important agents for bacteria inactivation, are detected over the entire plasma region. Large area treatment ability of this newly developed device is verified through bacteria inactivation experiment using E. coli. Sterilization experiment shows a large bacterial killing mark of 25 mm for a plasma treatment time of 10 s.

Current delivery and radiation yield in plasma flow switch-driven implosions

International Nuclear Information System (INIS)

Baker, W.L.; Degnan, J.H.; Beason, J.D.

1995-01-01

Vacuum inductive-store, plasma flow switch-driven implosion experiments have been performed using the Shiva Star capacitor bank (1300 μf, 3 nH, 120 kV, 9.4 MJ). A coaxial plasma gun arrangement is employed to store magnetic energy in the vacuum volume upstream of a dynamic discharge during the 3- to 4-μs rise of current from the capacitor bank. Motion of the discharge off the end of the inner conductor of the gun releases this energy to implode a coaxial cylindrical foil. The implosion loads are 5-cm-radius, 2-cm-long, 200 to 400 μg/cm 2 cylinders of aluminum or aluminized Formvar. With 5 MJ stored initially in the capacitor bank, more than 9 MA are delivered to the implosion load with a rise time of nearly 200 ns. The subsequent implosion results in a radiation output of 0.95 MJ at a power exceeding 5 TW (assuming isotropic emission). Experimental results and related two-dimensional magnetohydrodynamic simulations are discussed. 10 refs., 12 figs

Resonances in a periodically driven bosonic system

NARCIS (Netherlands)

Quelle, Anton; de Morais Smith, Cristiane

2017-01-01

Periodically driven systems are a common topic in modern physics. In optical lattices specifically, driving is at the origin of many interesting phenomena. However, energy is not conserved in driven systems, and under periodic driving, heating of a system is a real concern. In an effort to better

Global characteristics of zonal flows generated by ion temperature gradient driven turbulence in tokamak plasmas

International Nuclear Information System (INIS)

Miyato, Naoaki; Kishimoto, Yasuaki; Li, Jiquan

2004-08-01

Global structure of zonal flows driven by ion temperature gradient driven turbulence in tokamak plasmas is investigated using a global electromagnetic Landau fluid code. Characteristics of the coupled system of the zonal flows and the turbulence change with the safety factor q. In a low q region stationary zonal flows are excited and suppress the turbulence effectively. Coupling between zonal flows and poloidally asymmetric pressure perturbations via a geodesic curvature makes the zonal flows oscillatory in a high q region. Also we identify energy transfer from the zonal flows to the turbulence via the poloidally asymmetric pressure perturbations in the high q region. Therefore in the high q region the zonal flows cannot quench the turbulent transport completely. (author)

Plasma Turbulence Suppression and Transport Barrier Formation by Externally Driven RF Waves in Spherical Tokamaks

International Nuclear Information System (INIS)

Bruma, C.; Cuperman, S.C.; Komoshvili, K.

2002-01-01

Turbulent transport of heat and particles is the principle obstacle confronting controlled fusion today. Thus, we investigate quantitatively the suppression of turbulence and formation of transport barriers in spherical tokamaks by sheared electric fields generated by externally driven radio-frequency (RF) waves, in the frequency range o)A n o] < o)ci (e)A and o)ci are the Alfven and ion cyclotron frequencies). This investigation consists of the solution of the full-wave equation for a spherical tokamak in the presence of externally driven fast waves and the evaluation of the power dissipation by the mode-converted Alfven waves. This in turn, provides a radial flow shear responsible for the suppression of plasma turbulence. Thus, a strongly non-linear equation for the radial sheared electric field is solved, the turbulent transport suppression rate is evaluated and compared with the ion temperature gradient (ITG) instability increment. For illustration, the case of START-like device (Sykes 2000) is treated. Thus, (i) the exact D-shape cross-section is considered; (ii) additional kinetic (including Landau damping) and particle trapping effects are added to the resistive two-fluid dielectric tensor operator; (iii) a finite extension antenna located on the low-field-side of the plasma is considered; (iv) a rigorous 2.5 finite elements numerical code (Sewell 1993) is used; and (v) the turbulence and transport barrier generated as a result of wave-plasma interaction is evaluated

Measurement of Laser Plasma Instability (LPI) Driven Light Scattering from Plasmas Produced by Nike KrF Laser

Science.gov (United States)

Oh, Jaechul; Weaver, J. L.; Phillips, L.; Obenschain, S. P.; Schmitt, A. J.; Kehne, D. M.; Serlin, V.; Lehmberg, R. H.; McLean, E. A.; Manka, C. K.

2010-11-01

With short wavelength (248 nm), large bandwidth (1˜3 THz), and ISI beam smoothing, Nike KrF laser provides unique research opportunities and potential for direct-drive inertial confinement fusion. Previous Nike experiments observed two plasmon decay (TPD) driven signals from CH plasmas at the laser intensities above ˜2x10^15 W/cm^2 with total laser energies up to 1 kJ of ˜350 ps FWHM pulses. We have performed a further experiment with longer laser pulses (0.5˜4.0 ns FWHM) and will present combined results of the experiments focusing on light emission data in spectral ranges relevant to the Raman (SRS) and TPD instabilities. Time- or space-resolved spectral features of TPD were detected at different viewing angles and the absolute intensity calibrated spectra of thermal background were used to obtain blackbody temperatures in the plasma corona. The wave vector distribution in k-space of the participating TPD plasmons will be also discussed. These results show promise for the proposed direct-drive designs.

Laser-driven, magnetized quasi-perpendicular collisionless shocks on the Large Plasma Device

International Nuclear Information System (INIS)

Schaeffer, D. B.; Everson, E. T.; Bondarenko, A. S.; Clark, S. E.; Constantin, C. G.; Vincena, S.; Van Compernolle, B.; Tripathi, S. K. P.; Gekelman, W.; Niemann, C.; Winske, D.

2014-01-01

The interaction of a laser-driven super-Alfvénic magnetic piston with a large, preformed magnetized ambient plasma has been studied by utilizing a unique experimental platform that couples the Raptor kJ-class laser system [Niemann et al., J. Instrum. 7, P03010 (2012)] to the Large Plasma Device [Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] at the University of California, Los Angeles. This platform provides experimental conditions of relevance to space and astrophysical magnetic collisionless shocks and, in particular, allows a detailed study of the microphysics of shock formation, including piston-ambient ion collisionless coupling. An overview of the platform and its capabilities is given, and recent experimental results on the coupling of energy between piston and ambient ions and the formation of collisionless shocks are presented and compared to theoretical and computational work. In particular, a magnetosonic pulse consistent with a low-Mach number collisionless shock is observed in a quasi-perpendicular geometry in both experiments and simulations

Tailoring electron energy distribution functions through energy confinement in dual radio-frequency driven atmospheric pressure plasmas

Energy Technology Data Exchange (ETDEWEB)

O' Neill, C.; Waskoenig, J. [Centre for Plasma Physics, School of Maths and Physics, Queen' s University Belfast, Belfast BT7 1NN (United Kingdom); Gans, T. [Centre for Plasma Physics, School of Maths and Physics, Queen' s University Belfast, Belfast BT7 1NN (United Kingdom); York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom)

2012-10-08

A multi-scale numerical model based on hydrodynamic equations with semi-kinetic treatment of electrons is used to investigate the influence of dual frequency excitation on the effective electron energy distribution function (EEDF) in a radio-frequency driven atmospheric pressure plasma. It is found that variations of power density, voltage ratio, and phase relationship provide separate control over the electron density and the mean electron energy. This is exploited to directly influence both the phase dependent and time averaged effective EEDF. This enables tailoring the EEDF for enhanced control of non-equilibrium plasma chemical kinetics at ambient pressure and temperature.

Plasma heating by radiofrequency in the electron cyclotron resonance (ECR)

International Nuclear Information System (INIS)

Cunha Raposo, C. da; Aihara, S.; Universidade Estadual de Campinas

1982-01-01

The characteristics of the experimental set-up mounted in the Physical Institute of UFF (Brazil) to produce the gas ionization by radio-frequency are shown and its behaviour when confined by a mirror-geometry magnetic field is studied. The diagnostic is made by a langmuir probe and a prisme spectrogaph is used in order to verify the nature of the ionized helium gas and the degree of purity through its spectral lines. The argon ionization by R.f. is produced in the 'LISA' machine obtain a plasma column of approximatelly 60 cm length and with the Langmuir probe the study of the profile distribution of the plasma parameters such as: electron temperature and density and floating potencial in function of the magnetic field variation is made. The main focus is given to the fundamental electron cyclotron resonance (ECR). A new expression on the ion saturation current (I sub(is)) produced by radiofrequency is developed. (L.C.) [pt

Resonance probe; La sonde a resonance

Energy Technology Data Exchange (ETDEWEB)

Lepechinsky, D; Messiaen, A; Rolland, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1966-07-01

After a brief review of papers recently published on the resonance probe as a tool for plasma diagnostics, the main features of the theory proposed by one of us are recalled. In this theory the geometry of the resonator formed by the probe, the ion sheath and the plasma is explicitly taken into account with the quasi-static and cold plasma approximations. Some new results emerging from this theory are indicated and a comparison with experimental data obtained with a spherical probe placed in a quiescent mercury-vapour plasma is made. A good quantitative agreement has been observed, indicating that the theory is satisfactory and justifying the assumptions involved. Nevertheless it appears that in some cases experimental results can only be interpreted when non collisional damping phenomena are taken into consideration. (author) [French] Apres un apercu des etudes recemment publiees sur la sonde a resonance pour le diagnostic des plasmas, on rappelle l'essentiel de la theorie proposee par l'un de nous ou il est tenu compte explicitement de la geometrie du resonateur forme par le systeme sonde-gaine ionique-plasma dans l'approximation quasi-statique et du plasma froid. On indique quelques resultats nouveaux pouvant etre tires de cette theorie et on la confronte avec les donnees experimentales obtenues pour une sonde spherique placee dans un plasma de mercure en equilibre. Un tres bon accord quantitatif a ete constate, indiquant que la theorie est satisfaisante et justifiant les approximations faites dans celle-ci. Il apparait toutefois que certains resultats experimentaux ne peuvent etre interpretes qu'en tenant compte des phenomenes d'amortissement non collisionnels. (auteur)

Small scale structure of magnetospheric electron density through on-line tracking of plasma resonances

International Nuclear Information System (INIS)

Higel, B.

1978-01-01

The plasma resonance phenomena observed at fsub(pe), nfsub(ce), and fsub(qn) by the GEOS-1 S-301 relaxation sounder are identified through a pattern recognition software process implemented in a mini-computer which receives on-line the compressed data. First, this processing system distributes in real time fsub(pe) and fsub(ce) measurements to the ground media. Second, it drives and controls automatically the S-301 on-board experiment by sending appropriate telecommands: the tracking of resonances is performed by shortening the frequency sweeps to a narrow range centered on the resonance location. Examples of such tracking sequences are presented, exhibiting sampling rates of the electron density measurements from once every 22s (slowest rate) to once every 86 ms (highest rate available). The results give evidence of the existence of very small scale structures in the magnetospheric density, having characteristic sizes of the order of a few 10 2 m or/and a few 10 -1 s. The relative amplitude of these density fluctuations is typically 1%. Because of satellite spinning, fixed frequency sounding sequences allow to measure in a few seconds the directivity features of the plasma resonance signals. Examples of directional patterns in the plane perpendicular to the geomagnetic field are presented: the electrostatic nature of the waves received at fsub(pe), nfsub(ce), and fsub(qn) being consistent with these patterns, the corresponding k vector orientations become available. The Bernstein modes properties are used to interpret the nfsub(ce) and fsub(qn) results. (Auth.)

RF generated currents in a magnetized plasma using a slow wave structure

International Nuclear Information System (INIS)

Poole, B.R.; Cheo, B.R.; Kuo, S.P.; Tang, M.G.

1983-01-01

The generation of a dc current in a plasma by using RF waves is of importance for the operation of steadystate toroidal devices. An experimental investigation in the use of unidirectional, low frequency RF waves to drive currents has been made. Instead of using a natural plasma wave a slow wave guiding structure is used along the entire length of the plasma. When the RF wave is injected an increase in ionization and T/sub e/, and hence the background current is observed. However, the change depends on wave direction: The +k/sub z/ excitation yields a much larger electron current compared with the -k/sub z/ excitation indicating a net wave driven current. The measured modification in electron density and T/sub e/ is independent of wave direction. The current with a standing wave excitation generally falls at the average of the travelling wave (+ or - k/sub z/) driven currents. The net wave driven current is proportional to the feed power at approx. = 10 mA/kW. No saturation of the current is observed with feed powers up to 1 kW. Since the exciting structure is only 1 wavelength long, its k/sub z/ spectrum is relatively broad and hence no sharp resonances are observed as various plasma parameters and B/sub O/ are changed. There is no measurable difference between the power absorbed by the load resistors and the input power to the slow wave structure. Thus the current is driven by the wave field exclamation E exclamation 2 rather than the power absorbed in the plasma. The theoretical background and the physical mechanism is presented

MHD instabilities and their effects on plasma confinement in the large helical device plasmas

International Nuclear Information System (INIS)

Toi, K.

2002-01-01

MHD stability of NBI heated plasmas and impacts of MHD modes on plasma confinement are intensively studied in the Large Helical Device (LHD). Three characteristic MHD instabilities were observed, that is, (1) pressure driven modes excited in the plasma edge, (2) pressure driven mode in the plasma core, and (3) Alfven eigenmodes (AEs) driven by energetic ions. MHD mode excited in the edge region accompanies multiple satellites, and is called Edge Harmonic Modes (EHMs). EHM sometimes has a bursting character. The bursting EHM transiently decreases the stored energy by about 15 percent. In the plasma core region, m=2/n=1 pressure driven mode is typically destabilized. The mode often induces internal collapse in the higher beta regime more than 1 percent. The internal collapse appreciably affects the global confinement. Energetic ion driven AEs are often detected in NBI-heated LHD plasmas. Particular AE with the frequency 8-10 times larger than TAE-frequency was detected in high beta plasmas more than 2 percent. The AE may be related to helicity-induced AE. Excitation of these three types of MHD instabilities and their impacts on plasma confinement are discussed. (author)

Ballooning-mirror instability and internally driven Pc 4--5 wave events

International Nuclear Information System (INIS)

Cheng, C.Z.; Qian, Q.; Takahashi, K.; Lui, A.T.Y.

1994-03-01

A kinetic-MHD field-aligned eigenmode stability analysis of low frequency ballooning-mirror instabilities has been performed for anisotropic pressure plasma sin the magnetosphere. The ballooning mode is mainly a transverse wave driven unstable by pressure gradient in the bad curvature region. The mirror mode with a dominant compressional magnetic field perturbation is excited when the product of plasma beta and pressure anisotropy (P perpendicular /P parallel > 1) is large. From the AMPTE/CCE particle and magnetic field data observed during Pc 4--5 wave events the authors compute the ballooning-mirror instability parameters and perform a correlation study with the theoretical instability threshold. They find that compressional Pc 5 waves approximately satisfy the ballooning-mirror instability condition, and transverse Pc 4--5 waves are probably related to resonant ballooning instabilities with small pressure anisotropy

Electron injection and acceleration in the plasma bubble regime driven by an ultraintense laser pulse combined with using dense-plasma wall and block

Science.gov (United States)

Zhao, Xue-Yan; Xie, Bai-Song; Wu, Hai-Cheng; Zhang, Shan; Hong, Xue-Ren; Aimidula, Aimierding

2012-03-01

An optimizing and alternative scheme for electron injection and acceleration in the wake bubble driven by an ultraintense laser pulse is presented. In this scheme, the dense-plasma wall with an inner diameter matching the expected bubble size is placed along laser propagation direction. Meanwhile, a dense-plasma block dense-plasma is adhered inward transversely at some certain position of the wall. Particle-in-cell simulations are performed, which demonstrate that the block plays an important role in the first electron injection and acceleration. The result shows that a collimated electron bunch with a total number of about 4.04×108μm-1 can be generated and accelerated stably to 1.61 GeV peak energy with 2.6% energy spread. The block contributes about 50% to the accelerated electron injection bunch by tracing and sorting statistically the source.

Resonance-enhanced laser-induced plasma spectroscopy for sensitive elemental analysis: Elucidation of enhancement mechanisms

International Nuclear Information System (INIS)

Lui, S.L.; Cheung, N.H.

2002-01-01

When performing laser-induced plasma spectroscopy for elemental analysis, the analyte signal-to-noise ratio increased from four to over fifty if the plume was reheated by a dye laser pulse tuned to resonant absorption. Time-resolved studies showed that the enhancement was not due to resonance photoionization. Rather, efficient and controlled rekindling of a larger plume volume was the key mechanism. The signal-to-noise ratio further increased to over a hundred if the atmosphere was replaced by a low-pressure heavy inert gas. The ambient gas helped confine and thermally insulate the expanding vapor

RF plasma-driven hydrogen permeation through a biased iron membrane

International Nuclear Information System (INIS)

Banno, T.; Waelbroeck, F.; Winter, J.

1984-01-01

The steady-state RF plasma-driven hydrogen permeation through an electrically biased iron membrane has been investigated as a function of the bias potential Vsub(M) for membrane temperatures in the range of 150-400 0 C. Vsub(M) has been gradually increased positively from the floating potential of the membrane. The permeation flux decreases when Vsub(M) increases at low voltages: positive hydrogen ions are repelled. The membrane temperature does not influence this effect measurably. The permeation flux starts to increase when Vsub(M) is raised higher, i.e. when energetic electrons strike the surface. This phenomenon shows a pronounced temperature dependence - the enhancement is largest for the lowest temperatures. The effect is interpreted in terms of an electron-induced dissociation of hydrogen molecules on the membrane surface. (orig.)

Investigation of parameters of the working substance - low temperature plasma in the ionization resonator chamber of the RF reactive engine

International Nuclear Information System (INIS)

Vdovin, V.S.; Zajtzev, B.V.; Kobetz, A.F.; Bomko, V.A.; Rashkovan, V.M.; Bazyma, L.A.; Belokon, V.I.

2003-01-01

This paper is the extension of investigations of the RF engine designed for orientation and stabilization of the spacecrafts orbit, and it is undertaken for measuring of plasma parameters of RF discharge in the ionization resonator chamber. The experiments were performed at the frequency of 80 MHz on the model engine, in which a length of coaxial line with shortening capacities at the ends was used as the ionization resonator chamber. As the result of the experiments, conditions of the RF discharge ignition in the resonator chamber are studied; dependencies of plasma density and temperature versus applied power and working body pressure are obtained for various gases. The measurements of the thrust were performed at the special-purpose test bench

Quasilinear theory of the ordinary-mode electron-cyclotron resonance in plasmas

International Nuclear Information System (INIS)

Arunasalam, V.; Efthimion, P.C.; Hosea, J.C.; Hsuan, H.; Taylor, G.

1983-11-01

A coupled set of equations, one describing the time evolution of the ordinary-mode wave energy and the other describing the time evolution of the electron distribution function is presented. The wave damping is mainly determined by T/sub parallel/ while the radiative equilibrium is mainly an equipartition with T/sub perpendicular/. The time rate of change of T/sub perpendicular/, T/sub parallel/, particle (N 0 ), and current (J/sub parellel/) densities are examined for finite k/sub parallel/ electron-cyclotron-resonance heating of plasmas

The Transition to Collisionless Ion-temperature-gradient-driven Plasma Turbulence: A Dynamical Systems Approach

International Nuclear Information System (INIS)

Kolesnikov, R.A.; Krommes, J.A.

2004-01-01

The transition to collisionless ion-temperature-gradient-driven plasma turbulence is considered by applying dynamical systems theory to a model with ten degrees of freedom. Study of a four-dimensional center manifold predicts a ''Dimits shift'' of the threshold for turbulence due to the excitation of zonal flows and establishes the exact value of that shift in terms of physical parameters. For insight into fundamental physical mechanisms, the method provides a viable alternative to large simulations

Three-dimensional modeling of plasma edge transport and divertor fluxes during application of resonant magnetic perturbations on ITER

Czech Academy of Sciences Publication Activity Database

Schmitz, O.; Becoulet, M.; Cahyna, Pavel; Evans, T.E.; Feng, Y.; Frerichs, H.; Loarte, A.; Pitts, R.A.; Reiser, D.; Fenstermacher, M.E.; Harting, D.; Kirschner, A.; Kukushkin, A.; Lunt, T.; Saibene, G.; Reiter, D.; Samm, U.; Wiesen, S.

2016-01-01

Roč. 56, č. 6 (2016), č. článku 066008. ISSN 0029-5515 Institutional support: RVO:61389021 Keywords : resonant magnetic perturbations * plasma edge physics * 3D modeling * neutral particle physics * ITER * divertor heat and particle loads * ELM control Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 3.307, year: 2016 http://iopscience.iop.org/article/10.1088/0029-5515/56/6/066008/meta

Dynamics of runaway tails with time-dependent sub-Dreicer dc fields in magnetized plasmas

International Nuclear Information System (INIS)

Moghaddam-Taaheri, E.; Vlahos, L.

1987-01-01

The evolution of runaway tails driven by sub-Dreicer time-dependent dc fields in a magnetized plasma are studied numerically using a quasilinear code based on the Ritz--Galerkin method and finite elements. It is found that the runaway tail maintained a negative slope during the dc field increase. Depending on the values of the dc electric field at t = 0 and the electron gyrofrequency to the plasma frequency ratio the runaway tail became unstable to the anomalous Doppler resonance or remained stable before the saturation of the dc field at some maximum value. The systems that remained stable during this stage became unstable to the anomalous Doppler or the Cerenkov resonances when the dc field was kept at the saturation level or decreased. Once the instability is triggered, the runaway tail is isotropized

Dynamics of runaway tails with time-dependent sub-Dreicer dc fields in magnetized plasmas

Science.gov (United States)

Moghaddam-Taaheri, E.; Vlahos, L.

1987-01-01

The evolution of runaway tails driven by sub-Dreicer time-dependent dc fields in a magnetized plasma are studied numerically using a quasi-linear code based on the Ritz-Galerkin method and finite elements. It is found that the runaway tail maintained a negative slope during the dc field increase. Depending on the values of the dc electric field at t = 0 and the electron gyrofrequency to the plasma frequency ratio the runaway tail became unstable to the anomalous Doppler resonance or remained stable before the saturation of the dc field at some maximum value. The systems that remained stable during this stage became unstable to the anomalous Doppler or the Cerenkov resonances when the dc field was kept at the saturation level or decreased. Once the instability is triggered, the runaway tail is isotropized.

Influence of the electron cyclotron resonance plasma confinement on reducing the bremsstrahlung production of an electron cyclotron resonance ion source with metal-dielectric structures

International Nuclear Information System (INIS)

Schachter, L.; Dobrescu, S.; Stiebing, K. E.

2009-01-01

The influence of metal-dielectric (MD) layers (MD structures) inserted into the plasma chamber of an electron cyclotron resonance ion source (ECRIS) onto the production of electron bremsstrahlung radiation has been studied in a series of dedicated experiments at the 14 GHz ECRIS of the Institut fuer Kernphysik der Universitaet Frankfurt. The IKF-ECRIS was equipped with a MD liner, covering the inner walls of the plasma chamber, and a MD electrode, covering the plasma-facing side of the extraction electrode. On the basis of similar extracted currents of highly charged ions, significantly reduced yields of bremsstrahlung radiation for the 'MD source' as compared to the standard (stainless steel) source have been measured and can be explained by the significantly better plasma confinement in a MD source as compared to an ''all stainless steel'' ECRIS.

Behavior of Excited Argon Atoms in Inductively Driven Plasmas

International Nuclear Information System (INIS)

HEBNER, GREGORY A.; MILLER, PAUL A.

1999-01-01

Laser induced fluorescence has been used to measure the spatial distribution of the two lowest energy argon excited states, 1s 5 and 1s 4 , in inductively driven plasmas containing argon, chlorine and boron trichloride. The behavior of the two energy levels with plasma conditions was significantly different, probably because the 1s 5 level is metastable and the 1s 4 level is radiatively coupled to the ground state but is radiation trapped. The argon data is compared with a global model to identify the relative importance of processes such as electron collisional mixing and radiation trapping. The trends in the data suggest that both processes play a major role in determining the excited state density. At lower rfpower and pressure, excited state spatial distributions in pure argon were peaked in the center of the discharge, with an approximately Gaussian profile. However, for the highest rfpowers and pressures investigated, the spatial distributions tended to flatten in the center of the discharge while the density at the edge of the discharge was unaffected. The spatially resolved excited state density measurements were combined with previous line integrated measurements in the same discharge geometry to derive spatially resolved, absolute densities of the 1s 5 and 1s 4 argon excited states and gas temperature spatial distributions. Fluorescence lifetime was a strong fi.mction of the rf power, pressure, argon fraction and spatial location. Increasing the power or pressure resulted in a factor of two decrease in the fluorescence lifetime while adding Cl 2 or BCl 3 increased the fluorescence lifetime. Excited state quenching rates are derived from the data. When Cl 2 or BCl 3 was added to the plasma, the maximum argon metastable density depended on the gas and ratio. When chlorine was added to the argon plasma, the spatial density profiles were independent of chlorine fraction. While it is energetically possible for argon excited states to dissociate some of the

A physical model of Mirnov oscillations and plasma disruptions

International Nuclear Information System (INIS)

Cross, R.C.

1983-07-01

A physical model is proposed which accounts for the general behaviour of Mirnov oscillations and plasma disruptions in tokamak devices. The model also accounts for the stability of those devices which operate with edge safety factors less than 1.5. The model is based on the propagation of localized torsional Alfven and ion acoustic wavepackets. These packets remain phase coherent for considerable distances and are guided along helical field lines in toroidal plasmas, leading to the formation of standing waves on those field lines which close on themselves after one or more toroidal revolutions. Standing waves are driven resonantly on the rational surfaces by fluctuations in the poloidal field, causing localized heating and hence filamentation of the plasma current. This model indicates that Mirnov oscillations are produced by standing acoustic waves, while plasma disruptions occur as a result of the formation of MHD unstable current filaments

Effect of self-focusing on resonant third harmonic generation of laser in a rippled density plasma

International Nuclear Information System (INIS)

Kaur, Sukhdeep; Sharma, A. K.; Yadav, Sushila

2010-01-01

Resonant third harmonic generation by a Gaussian laser beam in a rippled density plasma is studied. The laser ponderomotive force induces second harmonic longitudinal velocity on electrons that couples with the static density ripple to produce a density perturbation at 2ω,2k+q, where ω and k are the frequency and wave number of the laser and q is the ripple wave number of the laser. This density perturbation beats with electron oscillatory velocity at ω,k-vector to produce a nonlinear current driving the third harmonic generation. In the regime of quadratic nonlinearity, the self-focusing of the laser enhances the third harmonic power. However, at higher intensity, plasma density is significantly reduced on the axis, detuning the third harmonic resonance and weakening the harmonic yield. Self-focusing causes enhancement in the efficiency of harmonic generation.

Surface plasmon resonance investigation of optical detection in plasma-modified phospholipid layers

International Nuclear Information System (INIS)

Park, Byoungchoo; Cho, Chanyoun; Choi, Kyoungho; Jeon, Honggoo

2012-01-01

We herein report on a study of surface plasmon resonance (SPR) in thin gold (Au) films coated with thin layers of phospholipid material, which had been exposed to an atmospheric pressure (AP) plasma containing both pure Ar and Ar mixed with O 2 (Ar/O 2 , 0.8%). The phospholipid material that we used for the SPR experiments was lecithin, and the AP plasma system was applied in air by means of a radio-frequency (RF) plasma generator. A thin (∼60 nm) film of Au and a thin (∼15 nm) layer of lecithin were deposited and attached to the face of a prism, and surface plasmon modes were excited along the interfaces of the prism-Au-lecithin-air system by means of prism coupling using a He-Ne Laser (632.8 nm). The experimental SPR reflectance curves of the Au-lecithin-air modes were found to be shifted towards those of the Au-air mode with increasing applications of AP RF plasma treatment. From the shifts in the SPR curves, we found that the estimated thickness of the lecithin layer treated with a pure Ar plasma showed a linear decrease with etching rate of about 3 nm per treatment while the thickness of the lecithin layer treated with a mixed Ar/O 2 plasma showed a tendency to saturate following a large initial decrease (ca. 14 nm). All these results demonstrate that the use of SPR sensing could facilitate the detection of extremely small variations in plasma-treated films of biomaterials.

Pacemaker-driven stochastic resonance on diffusive and complex networks of bistable oscillators

Energy Technology Data Exchange (ETDEWEB)

Perc, Matjaz; Gosak, Marko [Department of Physics, Faculty of Natural Sciences and Mathematics, University of Maribor, Koroska cesta 160, SI-2000 Maribor (Slovenia)], E-mail: matjaz.perc@uni-mb.si

2008-05-15

We study the phenomenon of stochastic resonance on diffusive, small-world and scale-free networks consisting of bistable overdamped oscillators. Important thereby is the fact that the external subthreshold periodic forcing is introduced only to a single oscillator of the network. Hence, the forcing acts as a pacemaker trying to impose its rhythm on the whole network through the unit to which it is introduced. Without the addition of additive spatiotemporal noise, however, the whole network, including the unit that is directly exposed to the pacemaker, remains trapped forever in one of the two stable steady states of the local dynamics. We show that the correlation between the frequency of subthreshold pacemaker activity and the response of the network is resonantly dependent on the intensity of additive noise. The reported pacemaker-driven stochastic resonance depends most significantly on the coupling strength and the underlying network structure. Namely, the outreach of the pacemaker obeys the classic diffusion law in the case of nearest-neighbor interactions, thus being proportional to the square root of the coupling strength, whereas it becomes superdiffusive by an appropriate small-world or scale-free topology of the interaction network. In particular, the scale-free topology is identified as being optimal for the dissemination of localized rhythmic activity across the whole network. Also, we show that the ratio between the clustering coefficient and the characteristic path length is the crucial quantity defining the ability of a small-world network to facilitate the outreach of the pacemaker-emitted subthreshold rhythm. We additionally confirm these findings by using the FitzHugh-Nagumo excitable system as an alternative to the bistable overdamped oscillator.

Pacemaker-driven stochastic resonance on diffusive and complex networks of bistable oscillators

International Nuclear Information System (INIS)

Perc, Matjaz; Gosak, Marko

2008-01-01

We study the phenomenon of stochastic resonance on diffusive, small-world and scale-free networks consisting of bistable overdamped oscillators. Important thereby is the fact that the external subthreshold periodic forcing is introduced only to a single oscillator of the network. Hence, the forcing acts as a pacemaker trying to impose its rhythm on the whole network through the unit to which it is introduced. Without the addition of additive spatiotemporal noise, however, the whole network, including the unit that is directly exposed to the pacemaker, remains trapped forever in one of the two stable steady states of the local dynamics. We show that the correlation between the frequency of subthreshold pacemaker activity and the response of the network is resonantly dependent on the intensity of additive noise. The reported pacemaker-driven stochastic resonance depends most significantly on the coupling strength and the underlying network structure. Namely, the outreach of the pacemaker obeys the classic diffusion law in the case of nearest-neighbor interactions, thus being proportional to the square root of the coupling strength, whereas it becomes superdiffusive by an appropriate small-world or scale-free topology of the interaction network. In particular, the scale-free topology is identified as being optimal for the dissemination of localized rhythmic activity across the whole network. Also, we show that the ratio between the clustering coefficient and the characteristic path length is the crucial quantity defining the ability of a small-world network to facilitate the outreach of the pacemaker-emitted subthreshold rhythm. We additionally confirm these findings by using the FitzHugh-Nagumo excitable system as an alternative to the bistable overdamped oscillator

Radial thermal diffusivity of toroidal plasma affected by resonant magnetic perturbations

International Nuclear Information System (INIS)

Kanno, Ryutaro; Nunami, Masanori; Satake, Shinsuke; Takamaru, Hisanori; Okamoto, Masao

2012-04-01

We investigate how the radial thermal diffusivity of an axisymmetric toroidal plasma is modified by effect of resonant magnetic perturbations (RMPs), using a drift kinetic simulation code for calculating the thermal diffusivity in the perturbed region. The perturbed region is assumed to be generated on and around the resonance surfaces, and is wedged in between the regular closed magnetic surfaces. It has been found that the radial thermal diffusivity χ r in the perturbed region is represented as χ r = χ r (0) {1 + c r parallel 2 >}. Here r parallel 2 > 1/2 is the strength of the RMPs in the radial directions, means the flux surface average defined by the unperturbed (i.e., original) magnetic field, χ r (0) is the neoclassical thermal diffusivity, and c is a positive coefficient. In this paper, dependence of the coefficient c on parameters of the toroidal plasma is studied in results given by the δ f simulation code solving the drift kinetic equation under an assumption of zero electric field. We find that the dependence of c is given as c ∝ ω b /ν eff m in the low collisionality regime ν eff b , where ν eff is the effective collision frequency, ω b is the bounce frequency and m is the particle mass. In case of ν eff > ω b , the thermal diffusivity χ r evaluated by the simulations becomes close to the neoclassical thermal diffusivity χ r (0) . (author)

Study of driven magnetic reconnection in a laboratory plasma

International Nuclear Information System (INIS)

Yamada, Masaaki; Ji, H.; Hsu, S.; Carter, T.; Kulsrud, R.; Bretz, N.; Jobes, F.; Ono, Yasushi; Perkins, F.

1998-01-01

The Magnetic Reconnection Experiment (MRX) has been constructed to investigate the fundamental physics of magnetic reconnection in a well controlled laboratory setting. This device creates an environment satisfying the criteria for a magnetohydrodynamic (MHD) plasma (S much-gt 1, ρ i much-lt L). The boundary conditions can be controlled externally, and experiments with fully three-dimensional reconnection are now possible. In the initial experiments, the effects of the third vector component of reconnecting fields have been studied. Two distinctively different shapes of neutral sheet current layers, depending on the third component, are identified during driven magnetic reconnection. Without the third component (anti-parallel or null-helicity reconnection), a thin double-Y shaped diffusion region is identified. A neutral sheet current profile is measured accurately to be as narrow as order ion gyro-radius. In the presence of an appreciable third component (co-helicity reconnection), an O-shaped diffusion region appears and grows into a spheromak configuration

Axisymmetric Alfvén resonances in a multi-component plasma at finite ion gyrofrequency

Directory of Open Access Journals (Sweden)

D. Yu. Klimushkin

2006-05-01

Full Text Available This paper deals with the spatial structure of zero azimuthal wave number ULF oscillations in a 1-D inhomogeneous multi-component plasma when a finite ion gyrofrequency is taken into account. Such oscillations may occur in the terrestrial magnetosphere as Pc1-3 waves or in the magnetosphere of the planet Mercury. The wave field was found to have a sharp peak on some magnetic surfaces, an analogy of the Alfvén (field line resonance in one-fluid MHD theory. The resonance can only take place for waves with frequencies in the intervals ω<ωch or Ω0<ω< ωcp, where ωch and ωcp are heavy and light ions gyrofrequencies, and Ω0 is a kind of hybrid frequency. Contrary to ordinary Alfvén resonance, the wave resonance under consideration takes place even at the zero azimuthal wave number. The radial component of the wave electric field has a pole-type singularity, while the azimuthal component is finite but has a branching point singularity on the resonance surface. The later singularity can disappear at some frequencies. In the region adjacent to the resonant surface the mode is standing across the magnetic shells.

Jet outflow and open field line measurements on the C-2U advanced beam-driven field-reversed configuration plasma experiment.

Science.gov (United States)

Sheftman, D; Gupta, D; Roche, T; Thompson, M C; Giammanco, F; Conti, F; Marsili, P; Moreno, C D

2016-11-01

Knowledge and control of the axial outflow of plasma particles and energy along open-magnetic-field lines are of crucial importance to the stability and longevity of the advanced beam-driven field-reversed configuration plasma. An overview of the diagnostic methods used to perform measurements on the open field line plasma on C-2U is presented, including passive Doppler impurity spectroscopy, microwave interferometry, and triple Langmuir probe measurements. Results of these measurements provide the jet ion temperature and axial velocity, electron density, and high frequency density fluctuations.

Characteristics of the resonant instability of surface electrostatic-ion-cyclotron waves in a semi-bounded warm magnetized dusty plasma

Energy Technology Data Exchange (ETDEWEB)

Hong, Woo-Pyo [Department of Electronics Engineering, Catholic University of Daegu, Hayang, 38430 (Korea, Republic of); Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr [Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 15588 (Korea, Republic of); Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180-3590 (United States)

2016-03-11

The influence of magnetic field and dust rotation on the resonant instability of surface electrostatic-ion-cyclotron wave is kinetically investigated in a semi-bounded warm magnetized dusty plasma. The dispersion relation and the temporal growth rate of the surface electrostatic-ion-cyclotron wave are derived by the specular-reflection boundary condition including the magnetic field and dust rotation effects. It is found that the instability domain decreases with an increase of the rotation frequency of elongated dust grain. It is also found that the dependence of the propagation wave number on the temporal growth rate is more significant for small ion cyclotron frequencies. In addition, it is shown that the scaled growth rate increases with an increase of the strength of magnetic field. The variation of the domain and magnitude of temporal growth rate due to the change of plasma parameters is also discussed. - Highlights: • The resonant instability of surface electrostatic-ion-cyclotron wave is investigated in a semi-bounded magnetized dusty plasma. • The dispersion relation and the temporal growth rate are derived by the specular-reflection condition. • The influence of magnetic field and dust rotation on the resonant instability is discussed.

High-Speed imaging of the plasma response to resonant magnetic perturbations in HBT-EP

International Nuclear Information System (INIS)

Angelini, Sarah M; Levesque, Jeffrey P; Mauel, Michael E; Navratil, Gerald A

2015-01-01

A Phantom v7.3 fast digital camera was used to study visible light fluctuations in the High Beta Tokamak–Extended Pulse (HBT–EP). This video data is the first to be used to analyze and understand the behavior of long wavelength kink perturbations in a wall-stabilized tokamak. The light was mostly comprised of Dα 656 nm light. Profiles of the plasma light at the midplane were hollow with a radial scale length of approximately 4 cm at the plasma edge. The fast camera was also used to measure the plasma’s response to applied helical magnetic perturbations. The programmed toroidal phase angle of the resonant magnetic perturbation (RMP) was directly inferred from the resulting images of the plasma response. The plasma response and the intensity of the RMP were compared under different conditions. The resulting amplitude correlations are consistent with previous measurements of the static response using an array of magnetic sensors. (paper)

Three-dimensional analysis of nonlinear plasma oscillation

International Nuclear Information System (INIS)

Miano, G.

1990-01-01

In an underdense plasma a large-amplitude plasma oscillation may be produced by the beating of two external and colinear electromagnetic waves with a frequency difference approximately equal to the plasma frequency - plasma beat wave (PBW) resonant mechanism. The plasma oscillations are driven by the ponderomotive force arising from the beating of the two imposed electromagnetic waves. In this paper two pump electromagnetic waves with arbitrary transverse profiles have been considered. The plasma is described by using the three dimensinal weakly relativistic fluid equations. The nonlinear plasma oscillation dynamics is studied by using the eulerian description, the averaging and the multiple time scale methods. Unlike the linear theory a strong cross field coupling between longitudinal ans transverse electric field components of the plasma oscillation comes out, resulting in a nonlinear phase change and energy transfer between the two components. Unlike the one-dimensional nonlinear theory, the nonlinear frequency shift is caused by relativistic effects as well as by convective effects and electromagnetic field generated from the three dimensional plasma oscillation. The large amplitude plasma oscillation dynamics produced by a bunched relativistic electron beam with arbitrary transverse profile - plasma wave field (PWF) - or by a high power single frequency short electromagnetic pulse with arbitrary transverse profile - electromagnetic plasma wake field (EPWF) - may be described by means of the present theory. (orig.)

Influence of the electron cyclotron resonance plasma confinement on reducing the bremsstrahlung production of an electron cyclotron resonance ion source with metal-dielectric structures.

Science.gov (United States)

Schachter, L; Stiebing, K E; Dobrescu, S

2009-01-01

The influence of metal-dielectric (MD) layers (MD structures) inserted into the plasma chamber of an electron cyclotron resonance ion source (ECRIS) onto the production of electron bremsstrahlung radiation has been studied in a series of dedicated experiments at the 14 GHz ECRIS of the Institut für Kernphysik der Universität Frankfurt. The IKF-ECRIS was equipped with a MD liner, covering the inner walls of the plasma chamber, and a MD electrode, covering the plasma-facing side of the extraction electrode. On the basis of similar extracted currents of highly charged ions, significantly reduced yields of bremsstrahlung radiation for the "MD source" as compared to the standard (stainless steel) source have been measured and can be explained by the significantly better plasma confinement in a MD source as compared to an "all stainless steel" ECRIS.

Design of an induction linac driven CARM [Cyclotron Auto Resonance Maser] oscillator at 250 GHz

International Nuclear Information System (INIS)

Caplan, M.; Kulke, B.

1990-01-01

We present the design of a 250 GHz, 400 MW Cyclotron Auto Resonance Maser (CARM) oscillator driven by a 1 KA, 2 MeV electron beam produced by the induction linac at the ARC facility of LLNL. The oscillator circuit is designed as a feedback amplifier operating in the TE 11 mode at ten times cutoff terminated at each end with Bragg reflectors. Theory and cold test results are in good agreement for a manufactured Bragg reflector using 50 μm corrugations to ensure mode purity. The CARM is to be operational by February 1990. 3 figs., 2 tabs

Temperature dependence of the cosphi conductance in Josephson tunnel junctions determined from plasma resonance experiments

DEFF Research Database (Denmark)

Pedersen, Niels Falsig; Sørensen, O. H.; Mygind, Jesper

1978-01-01

The microwave response at 9 GHz of Sn-O-Sn tunnel-junction current biased at zero dc voltage has been measured just below the critical temperature Tc of the Sn films. The temperature dependence of the cosφ conductance is determined from the resonant response at the junction plasma frequency fp...

Effect of ECRH and resonant magnetic fields on formation of magnetic islands in the T-10 tokamak plasma

Science.gov (United States)

Shestakov, E. A.; Savrukhin, P. V.

2017-10-01

Experiments in the T-10 tokamak demonstrated possibility of controlling the plasma current during disruption instability using the electron cyclotron resonance heating (ECRH) and the controlled operation of the ohmic current-holding system. Quasistable plasma discharge with repeating sawtooth oscillations can be restored after energy quench using auxiliary ECRH power when PEC / POH > 2-5. The external magnetic field generation system consisted of eight saddle coils that were arranged symmetrically relative to the equatorial plane of the torus outside of the vacuum vessel of the T-10 tokamak to study the possible resonant magnetic field effects on the rotation frequency of magnetic islands. The saddle coils power supply system is based on four thyristor converters with a total power of 300 kW. The power supply control system is based on Siemens S7 controllers. As shown by preliminary experiments, the interaction efficiency of external magnetic fields with plasma depends on the plasma magnetic configuration. Optimal conditions for slowing the rotation of magnetic islands were determined. Additionally, the direction of the error magnetic field in the T-10 tokamak was determined, and the threshold value of the external magnetic field was determined.

Nonlinear Plasma Response to Resonant Magnetic Perturbation in Rutherford Regime

Science.gov (United States)

Zhu, Ping; Yan, Xingting; Huang, Wenlong

2017-10-01

Recently a common analytic relation for both the locked mode and the nonlinear plasma response in the Rutherford regime has been developed based on the steady-state solution to the coupled dynamic system of magnetic island evolution and torque balance equations. The analytic relation predicts the threshold and the island size for the full penetration of resonant magnetic perturbation (RMP). It also rigorously proves a screening effect of the equilibrium toroidal flow. In this work, we test the theory by solving for the nonlinear plasma response to a single-helicity RMP of a circular-shaped limiter tokamak equilibrium with a constant toroidal flow, using the initial-value, full MHD simulation code NIMROD. Time evolution of the parallel flow or ``slip frequency'' profile and its asymptotic approach to steady state obtained from the NIMROD simulations qualitatively agree with the theory predictions. Further comparisons are carried out for the saturated island size, the threshold for full mode penetration, as well as the screening effects of equilibrium toroidal flow in order to understand the physics of nonlinear plasma response in the Rutherford regime. Supported by National Magnetic Confinement Fusion Science Program of China Grants 2014GB124002 and 2015GB101004, the 100 Talent Program of the Chinese Academy of Sciences, and U.S. Department of Energy Grants DE-FG02-86ER53218 and DE-FC02-08ER54975.

A study of the effect on human mesenchymal stem cells of an atmospheric pressure plasma source driven by different voltage waveforms

Science.gov (United States)

Laurita, R.; Alviano, F.; Marchionni, C.; Abruzzo, P. M.; Bolotta, A.; Bonsi, L.; Colombo, V.; Gherardi, M.; Liguori, A.; Ricci, F.; Rossi, M.; Stancampiano, A.; Tazzari, P. L.; Marini, M.

2016-09-01

The effect of an atmospheric pressure non-equilibrium plasma on human mesenchymal stem cells was investigated. A dielectric barrier discharge non-equilibrium plasma source driven by two different high-voltage pulsed generators was used and cell survival, senescence, proliferation, and differentiation were evaluated. Cells deprived of the culture medium and treated with nanosecond pulsed plasma showed a higher mortality rate, while higher survival and retention of proliferation were observed in cells treated with microsecond pulsed plasma in the presence of the culture medium. While a few treated cells showed the hallmarks of senescence, unexpected delayed apoptosis ensued in cells exposed to plasma-treated medium. The plasma treatment did not change the expression of OCT4, a marker of mesenchymal stem cell differentiation.

Theoretical performance of plasma driven railguns

Science.gov (United States)

Thio, Y. C.; McNab, I. R.; Condit, W. C.

1983-07-01

The overall efficiency of a railgun launch system is the product of efficiencies of its subsystems: prime mover, energy storage, pulse forming network, and accelerator. In this paper, the efficiency of the accelerator is examined in terms of the processes occurring in the accelerator. The principal loss mechanisms include Joule heating in the plasma, in the rails, kinetic energy of the driving plasma and magnetic energy remaining in the accelerator after projectile exit. The mass of the plasma and the atomic weight of the ionic species are important parameters in determining the energy loss in the plasma. Techniques are developed for selecting these parameters of minimize this loss.

Resonant interaction of electromagnetic wave with plasma layer and overcoming the radiocommunication blackout problem

Science.gov (United States)

Bogatskaya, A. V.; Klenov, N. V.; Tereshonok, M. V.; Adjemov, S. S.; Popov, A. M.

2018-05-01

We present an analysis of the possibility of penetrating electromagnetic waves through opaque media using an optical-mechanical analogy. As an example, we consider the plasma sheath surrounding the vehicle as a potential barrier and analyze the overcoming of radiocommunication blackout problem. The idea is to embed a «resonator» between the surface on the vehicle and plasma sheath which is supposed to provide an effective tunneling of the signal to the receiving antenna. We discuss the peculiarities of optical mechanical analogy applicability and analyze the radio frequency wave tunneling regime in detail. The cases of normal and oblique incidence of radiofrequency waves on the vehicle surface are studied.

Role of impurity dynamics in resistivity-gradient-driven turbulence and tokamak edge plasma phenomena

International Nuclear Information System (INIS)

Hahm, T.S.; Diamond, P.H.; Terry, P.W.; Garcia, L.; Carreras, B.A.

1986-03-01

The role of impurity dynamics in resistivity gradient driven turbulence is investigated in the context of modeling tokamak edge plasma phenomena. The effects of impurity concentration fluctuations and gradients on the linear behavior of rippling instabilities and on the nonlinear evolution and saturation of resistivity gradient driven turbulence are studied both analytically and computationally. At saturation, fluctuation levels and particle and thermal diffusivities are calculated. In particular, the mean-square turbulent radial velocity is given by 2 > = (E 0 L/sub s/B/sub z/) 2 (L/sub/eta/ -1 + L/sub z -1 ) 2 . Thus, edged peaked impurity concentrations tend to enhance the turbulence, while axially peaked concentrations tend to quench it. The theoretical predictions are in semi-quantitative agreement with experimental results from the TEXT, Caltech, and Tosca tokamaks. Finally, a theory of the density clamp observed during CO-NBI on the ISX-B tokamak is proposed

Self-excited nonlinear plasma series resonance oscillations in geometrically symmetric capacitively coupled radio frequency discharges

International Nuclear Information System (INIS)

Donko, Z.; Schulze, J.; Czarnetzki, U.; Luggenhoelscher, D.

2009-01-01

At low pressures, nonlinear self-excited plasma series resonance (PSR) oscillations are known to drastically enhance electron heating in geometrically asymmetric capacitively coupled radio frequency discharges by nonlinear electron resonance heating (NERH). Here we demonstrate via particle-in-cell simulations that high-frequency PSR oscillations can also be excited in geometrically symmetric discharges if the driving voltage waveform makes the discharge electrically asymmetric. This can be achieved by a dual-frequency (f+2f) excitation, when PSR oscillations and NERH are turned on and off depending on the electrical discharge asymmetry, controlled by the phase difference of the driving frequencies

First observations of acceleration of injected electrons in a laser plasma beatwave experiment

International Nuclear Information System (INIS)

Ebrahim, N.A.; Martin, F.; Bordeur, P.; Heighway, E.A.; Matte, J.P.; Pepin, H.; Lavigne, P.

1986-01-01

The first experimental observations of acceleration of injected electrons in a laser driven plasma beatwave are presented. The plasma waves were excited in an ionized gas jet, using a short pulse high intensity CO 2 laser with two collinearly propagating beams (at λ = 9.6 μm and 10.6 μm) to excite a fast wave (v/sub p/ = c). The source of electrons was a laser plasma produced on an aluminum slab target by a third, synchronized CO 2 laser beam. A double-focusing dipole magnet was used to energy select and inject electrons into the beatwave, and a second magnetic spectrograph was used to analyze the accelerated electrons. Electron acceleration was only observed when the appropriate resonant plasma density was produced (∼ 10 17 cm -3 ), the two laser lines were incident on the plasma, and electrons were injected into this plasma from an external source

Drift resonance and stability of the Io plasma torus

Science.gov (United States)

Zhan, Jie; Hill, T. W.

2000-03-01

The observed local time asymmetry of the Io plasma torus is generally attributed to the presence of a persistent dawn-to-dusk electric field in the Jovian magnetosphere. The local time asymmetry is modulated at the System 3 rotation period of Jupiter's magnetic field, suggesting that the dawn-to-dusk electric field may be similarly modulated. We argue that such a System 3 modulation would have a profound disruptive effect on the observed torus structure if the torus were to corotate at exactly the System 3 rate: the torus would be a resonantly forced harmonic oscillator, and would disintegrate in a few rotation periods, contrary to observations. This destabilizing effect is independent of, and in addition to, the more familiar effect of the centrifugal interchange instability, which is also capable of disrupting the torus in a few rotation periods in the absence of other effects. We conclude that the observed (few percent) corotation lag of the torus is essential to preserving the observed long-lived torus structure by detuning the resonant frequency (the torus drift frequency) relative to the forcing frequency (System 3). A possible outcome of this confinement mechanism is a residual radial oscillation of the torus at the beat period (~10 days) between System 3 and the torus drift period.

Dynamically balanced, hydraulically driven compressor/pump apparatus for resonant free piston Stirling engines

Science.gov (United States)

Corey, John A.

1984-05-29

A compressor, pump, or alternator apparatus is designed for use with a resonant free piston Stirling engine so as to isolate apparatus fluid from the periodically pressurized working fluid of the Stirling engine. The apparatus housing has a first side closed by a power coupling flexible diaphragm (the engine working member) and a second side closed by a flexible diaphragm gas spring. A reciprocally movable piston is disposed in a transverse cylinder in the housing and moves substantially at right angles relative to the flexible diaphragms. An incompressible fluid fills the housing which is divided into two separate chambers by suitable ports. One chamber provides fluid coupling between the power diaphragm of the RFPSE and the piston and the second chamber provides fluid coupling between the gas spring diaphragm and the opposite side of the piston. The working members of a gas compressor, pump, or alternator are driven by the piston. Sealing and wearing parts of the apparatus are mounted at the external ends of the transverse cylinder in a double acting arrangement for accessibility. An annular counterweight is mounted externally of the reciprocally movable piston and is driven by incompressible fluid coupling in a direction opposite to the piston so as to damp out transverse vibrations.

Supersonic Ionization Wave Driven by Radiation Transport in a Short-Pulse Laser-Produced Plasma

International Nuclear Information System (INIS)

Ditmire, T.; Gumbrell, E.T.; Smith, R.A.; Mountford, L.; Hutchinson, M.H.

1996-01-01

Through the use of an ultrashort (2ps) optical probe, we have time resolved the propagation of an ionization wave into solid fused silica. This ionization wave results when a plasma is created by the intense irradiation of a solid target with a 2ps laser pulse. We find that the velocity of the ionization wave is consistent with radiation driven thermal transport, exceeding the velocity expected from simple electron thermal conduction by nearly an order of magnitude. copyright 1996 The American Physical Society

Resonant mode for a dc plasma spray torch by means of pressure–voltage coupling: application to synchronized liquid injection

International Nuclear Information System (INIS)

Krowka, J; Rat, V; Coudert, J F

2013-01-01

Electric arc instabilities in dc plasma torches result in non-homogeneous treatment of nanosized solid particles injected into the plasma jets. In the particular case of suspension plasma spraying, large discrepancies in the particles trajectories and thermal histories make the control of coating properties more difficult to achieve. In this paper, a new approach of arc dynamics highlights the existence of different resonant modes and the possibility of their coupling. This study leads us to design a special plasma torch working in a very regular pulsed regime. Then, an innovative injection system based on the drop-on-demand method synchronized with the plasma oscillations is presented as an efficient method to control the dynamics of plasma/particles interactions. (paper)

Axisymmetric Alfvén resonances in a multi-component plasma at finite ion gyrofrequency

Directory of Open Access Journals (Sweden)

D. Yu. Klimushkin

2006-05-01

Full Text Available This paper deals with the spatial structure of zero azimuthal wave number ULF oscillations in a 1-D inhomogeneous multi-component plasma when a finite ion gyrofrequency is taken into account. Such oscillations may occur in the terrestrial magnetosphere as Pc1-3 waves or in the magnetosphere of the planet Mercury. The wave field was found to have a sharp peak on some magnetic surfaces, an analogy of the Alfvén (field line resonance in one-fluid MHD theory. The resonance can only take place for waves with frequencies in the intervals ω<ω_ch or Ω₀<ω< ω_cp, where ω_ch and ω_cp are heavy and light ions gyrofrequencies, and Ω₀ is a kind of hybrid frequency. Contrary to ordinary Alfvén resonance, the wave resonance under consideration takes place even at the zero azimuthal wave number. The radial component of the wave electric field has a pole-type singularity, while the azimuthal component is finite but has a branching point singularity on the resonance surface. The later singularity can disappear at some frequencies. In the region adjacent to the resonant surface the mode is standing across the magnetic shells.

A quasilinear formulation of turbulence driven current

Energy Technology Data Exchange (ETDEWEB)

McDevitt, C. J.; Tang, Xian-Zhu; Guo, Zehua [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2014-02-15

Non-inductive current drive mechanisms, such as the familiar neoclassical bootstrap current correspond to an essential component to the realization of steady state tokamak operation. In this work, we discuss a novel collisionless mechanism through which a mean plasma current may be driven in the presence of microturbulence. In analogy with the traditional neoclassical bootstrap current drive mechanism, in which the collisional equilibrium established between trapped and passing electrons results in the formation of a steady state plasma current, here we show that resonant scattering of electrons by drift wave microturbulence provides an additional means of determining the equilibrium between trapped and passing electrons. The resulting collisionless equilibrium is shown to result in the formation of an equilibrium current whose magnitude is a function of the thermodynamic forces. A mean field formulation is utilized to incorporate the above components into a unified framework through which both collisional as well as collisionless current drive mechanisms may be self-consistently treated. Utilizing a linearized Fokker-Planck collision operator, the plasma current in the presence of both collisions as well as turbulent stresses is computed, allowing for the relative strength of these two mechanisms to be quantified as a function of collisionality and fluctuation amplitude.

A quasilinear formulation of turbulence driven current

International Nuclear Information System (INIS)

McDevitt, C. J.; Tang, Xian-Zhu; Guo, Zehua

2014-01-01

Non-inductive current drive mechanisms, such as the familiar neoclassical bootstrap current correspond to an essential component to the realization of steady state tokamak operation. In this work, we discuss a novel collisionless mechanism through which a mean plasma current may be driven in the presence of microturbulence. In analogy with the traditional neoclassical bootstrap current drive mechanism, in which the collisional equilibrium established between trapped and passing electrons results in the formation of a steady state plasma current, here we show that resonant scattering of electrons by drift wave microturbulence provides an additional means of determining the equilibrium between trapped and passing electrons. The resulting collisionless equilibrium is shown to result in the formation of an equilibrium current whose magnitude is a function of the thermodynamic forces. A mean field formulation is utilized to incorporate the above components into a unified framework through which both collisional as well as collisionless current drive mechanisms may be self-consistently treated. Utilizing a linearized Fokker-Planck collision operator, the plasma current in the presence of both collisions as well as turbulent stresses is computed, allowing for the relative strength of these two mechanisms to be quantified as a function of collisionality and fluctuation amplitude

Fluid simulations of ∇Te-driven turbulence and transport in boundary plasmas

International Nuclear Information System (INIS)

Xu, X.Q.; Cohen, R.H.

1993-01-01

This paper is a report on simulations of a new drift wave type instability driven by the electron temperature gradient in tokamak scrapeoff-layers (SOL). A 2D(x,y) fluid code has been developed in order to explore the anomalous transport in the boundary plasmas. The simulation consists of a set of fluid equations (in the electrostatic limit) for the vorticity ∇ perpendicular 2 φ, the electron density n e and the temperature T e in a shearless plasma slab confined by a uniform, straight magnetic field B z with two diverter (or limiter) plates intercepting the magnetic field. The model has two regions separated by a magnetic separatrix: in the edge region inside the separatrix, the model is periodic along the magnetic field while in the SOL region outside the separatrix, the magnetic field is taken to be of finite length with model (logical sheath) boundary conditions at diverter (or limiter) plates. The simulation results show that the observed linear instability agrees well with theory, and that a saturated state of turbulence is reached. In saturated turbulence, clear evidence of the expected long-wavelength mode penetration into the edge is seen, an inverse cascade of wave energy (toward both long wavelengths and low frequencies) is observed. The simulation results also show that amplitudes of potential and the electron temperature fluctuations are somewhat above and the heat flux are somewhat below those of the simplest mixing-length estimates. The results from the self-consistent simulations to determine the microturbulent SOL electron temperature profile agree reasonably with the experimental measurements. The effects on the mode of neutral gas collisions at the divertor sheath and comparisons with the ionization driven turbulence are discussed

Enhanced laser-energy coupling to dense plasmas driven by recirculating electron currents

Science.gov (United States)

Gray, R. J.; Wilson, R.; King, M.; Williamson, S. D. R.; Dance, R. J.; Armstrong, C.; Brabetz, C.; Wagner, F.; Zielbauer, B.; Bagnoud, V.; Neely, D.; McKenna, P.

2018-03-01

The absorption of laser energy and dynamics of energetic electrons in dense plasma is fundamental to a range of intense laser-driven particle and radiation generation mechanisms. We measure the total reflected and scattered laser energy as a function of intensity, distinguishing between the influence of pulse energy and focal spot size on total energy absorption, in the interaction with thin foils. We confirm a previously published scaling of absorption with intensity by variation of laser pulse energy, but find a slower scaling when changing the focal spot size. 2D particle-in-cell simulations show that the measured differences arise due to energetic electrons recirculating within the target and undergoing multiple interactions with the laser pulse, which enhances absorption in the case of large focal spots. This effect is also shown to be dependent on the laser pulse duration, the target thickness and the electron beam divergence. The parameter space over which this absorption enhancement occurs is explored via an analytical model. The results impact our understanding of the fundamental physics of laser energy absorption in solids and thus the development of particle and radiation sources driven by intense laser–solid interactions.

Spatial profiling of ion and neutral excitation in noble gas electron cyclotron resonance plasmas

International Nuclear Information System (INIS)

Rhoades, R.L.; Gorbatkin, S.M.

1994-01-01

Optical emission from neutrals and ions of several noble gases has been profiled in an electron cyclotron resonance plasma system. In argon plasmas with a net microwave power of 750 W, the neutral (696.5-nm) and ion (488-nm) emission profiles are slightly center peaked at 0.32 mTorr and gradually shift to a hollow appearance at 2.5 mTorr. Neon profiles show a similar trend from 2.5 to 10.0 mTorr. For the noble gases, transition pressure scales with the ionization potential of the gas, which is consistent with neutral depletion. Studies of noble gas mixtures, however, indicate that neutral depletion is not always dominant in the formation of hollow profiles. For Kr/Ar, Ar/Ne, and Ne/He plasmas, the majority gas tends to set the overall shape of the profile at any given pressure. For the conditions of the current system, plasma density appears to be more dominant than electron temperature in the formation of hollow profiles. The general method described is also a straightforward, inexpensive technique for measuring the spatial distribution of power deposited in plasmas, particularly where absolute scale can be calibrated by some other means

Observation of inward and outward particle convection in the core of electron cyclotron heated and current driven plasmas in the Tokamak a Configuration Variable

International Nuclear Information System (INIS)

Furno, I.; Weisen, H.

2003-01-01

In the Tokamak a Configuration Variable [F. Hofmann, J.B. Lister, M. Anton et al., Plasma Phys. Controlled Fusion 36, B277 (1994)], inward or outward convection in the core of electron cyclotron heated and current driven plasmas is observed, depending on discharge conditions. In sawtoothing discharges with central electron cyclotron heating, outward convection is observed when a quasicontinuous m=1 kink mode is present, resulting in inverted sawteeth on the central electron density, while in the absence thereof, inward convection between successive sawtooth crashes leads to 'normal' sawteeth. The occurrence of a kink mode depends sensitively on plasma triangularity. When sawteeth are stabilized with central co- or counterelectron cyclotron current drive, stationary hollow electron density profiles are observed in the presence of m=1 modes, while peaked or flat profiles are observed in magnetohydrodynamic quiescent discharges. The observation of peaked density profiles in fully electron cyclotron driven plasmas demonstrates that pinch processes other than the Ware pinch must be responsible for these phenomena

Review on resonance cone fields

International Nuclear Information System (INIS)

Ohnuma, Toshiro.

1980-02-01

Resonance cone fields and lower hybrid heating are reviewed in this report. The resonance cone fields were reported by Fisher and Gould, and they proposed the use of the measurement of resonance cones and structure as a diagnostic tool to determine the plasma density and electron temperature in magnetoplasma. After the resonance cone, a wave-like disturbance persists. Ohnuma et al. have measured bending, reflection and ducting of resonance cones in detail. The thermal modes in inhomogeneous magnetoplasma were seen. The reflection of thermal mode near an electron plasma frequency layer and an insulating plate has been observed. The non-linear effects of resonance cones is reported. Monochromatic electron beam produces the noise of broad band whistler mode. Lower hybrid waves have been the subject of propagation from the edge of plasma to the lower hybrid layer. Linear lower hybrid waves were studied. The lower hybrid and ion acoustic waves radiated from a point source were observed. The parametric decay of finite-extent, cold electron plasma waves was studied. The lower hybrid cone radiated from a point source going along magnetic field lines was observed. Several experimental data on the lower hybrid heating in tokamak devices have been reported. The theories on resonance cones and lower hybrid waves are introduced in this report. (Kato, T.)

Calculation of self-absorption coefficients of calcium resonance lines in the case of a CaCl2-water plasma

International Nuclear Information System (INIS)

Hannachi, R.; Cressault, Y.; Teulet, Ph.; Gleizes, A.; Lakhdar, Z. Ben

2008-01-01

The resonance escape factors for the lines emitted by a neutral calcium atom Ca I at 4226.73 A and of ionic calcium Ca II at 3933.66 A and at 3968.47 A are calculated assuming a Voigt profile and in the case of CaCl 2 -water plasma. The dependence of the escape factor on the optical thickness f 0 from the line center which itself depends on the two main spectral line shape broadening mechanisms (pressure and Doppler effects) are considered. The variation of the resonance escape factors with the temperature, the CaCl 2 molar proportion and the size of the plasma are also investigated. This calculation is useful for the application of Laser-Induced Breakdown Spectroscopy in the quantitative analysis of elemental composition. Its application allows us to reduce the non-linearities in the relation between resonance lines intensities of calcium in our case and its concentration

First Observation of the High Field Side Sawtooth Crash and Heat Transfer during Driven Reconnection Processes in Magnetically Confined Plasmas

International Nuclear Information System (INIS)

Park, HK; Luhmann, NC; Donne, AJH; Classen, IGJ; Domier, CW; Mazzucato, E; Munsat, T; van de Pol, MJ; Xia, Z

2005-01-01

High resolution (temporal and spatial), two-dimensional images of electron temperature fluctuations during sawtooth oscillations were employed to study driven reconnection processes in magnetically confined toroidal plasmas. The combination of kink and local pressure driven instabilities leads to an 'X-point' reconnection process that is localized in the toroidal and poloidal planes. The reconnection is not always confined to the magnetic surfaces with minimum energy. The heat transport process from the core is demonstrated to be highly collective rather than stochastic

The influence of ambipolarity on plasma confinement and on the performance of electron cyclotron resonance ion sources.

Science.gov (United States)

Schachter, L; Dobrescu, S; Stiebing, K E; Thuillier, T; Lamy, T

2008-02-01

Charge diffusion in an electron cyclotron resonance ion source (ECRIS) discharge is usually characterized by nonambipolar behavior. While the ions are transported to the radial walls, electrons are lost axially from the magnetic trap. Global neutrality is maintained via compensating currents in the conducting walls of the vacuum chamber. It is assumed that this behavior reduces the ion breeding times compared to a truly ambipolar plasma. We have carried out a series of dedicated experiments in which the ambipolarity of the ECRIS plasma was influenced by inserting special metal-dielectric structures (MD layers) into the plasma chamber of the Frankfurt 14 GHz ECRIS. The measurements demonstrate the positive influence on the source performance when the ECR plasma is changed toward more ambipolar behavior.

Studies of energetic-ion-driven MHD instabilities in helical plasmas with low magnetic shear

International Nuclear Information System (INIS)

Yamamoto, S.; Ascasibar, E.; Jimenez-Gomez, R.

2012-11-01

We discuss the features of energetic-ion-driven MHD instabilities such as Alfvén eigenmodes (AEs) in three-dimensional magnetic configuration with low magnetic shear and low toroidal field period number (N p ) that are characteristic of advanced helical plasmas. Comparison of experimental and numerical studies in Heliotron J with those in TJ-II indicates that the most unstable AE is global AE (GAE) in low magnetic shear configuration in spite of the iota and the helicity-induced AE (HAE) is also the most unstable AE in the high iota configuration. (author)

Mode Coupling and Nonlinear Resonances of MEMS Arch Resonators for Bandpass Filters

KAUST Repository

Hajjaj, Amal Z.; Hafiz, Md Abdullah Al; Younis, Mohammad I.

2017-01-01

the passband to the stopband. The concept is demonstrated based on an electrothermally tuned and electrostatically driven MEMS arch resonator operated in air. The in-plane resonator is fabricated from a silicon-on-insulator wafer with a deliberate curvature

Fermi-edge transmission resonance in graphene driven by a single Coulomb impurity.

Science.gov (United States)

Karnatak, Paritosh; Goswami, Srijit; Kochat, Vidya; Pal, Atindra Nath; Ghosh, Arindam

2014-07-11

The interaction between the Fermi sea of conduction electrons and a nonadiabatic attractive impurity potential can lead to a power-law divergence in the tunneling probability of charge through the impurity. The resulting effect, known as the Fermi edge singularity (FES), constitutes one of the most fundamental many-body phenomena in quantum solid state physics. Here we report the first observation of FES for Dirac fermions in graphene driven by isolated Coulomb impurities in the conduction channel. In high-mobility graphene devices on hexagonal boron nitride substrates, the FES manifests in abrupt changes in conductance with a large magnitude ≈e(2)/h at resonance, indicating total many-body screening of a local Coulomb impurity with fluctuating charge occupancy. Furthermore, we exploit the extreme sensitivity of graphene to individual Coulomb impurities and demonstrate a new defect-spectroscopy tool to investigate strongly correlated phases in graphene in the quantum Hall regime.

Plasma instability issues for ITER and their possible impact on plasma performance

International Nuclear Information System (INIS)

Houlberg, W.A.; Campbell, D.

2009-01-01

Full text: There are many types of plasma instabilities that may affect ITER performance. Prediction of their impact, however, is complicated by scaling relative to present plasmas. Here we summarize some of the potential impacts of a variety of instabilities on ITER performance and the uncertainties in evaluating those impacts. ELMs are one of the most significant issues because of the high localized heat loads on the plasma facing components walls caused by the filamentary structures. ITER presently plans to employ two methods to attempt to amelioriate the localized damage from large ELMS: resonant magnetic perturbations and pellet pacing. In either case, the net effect on confinement must be minimized relative to the expected confinement under natural ELMy conditions. Pacing ELMs with high frequency pellet injection raises at least two fundamental physics questions: i) how effective are very localized perturbations from the pellet cloud at triggering ELMs?, and ii) can we assure that the local perturbation does not lock the ELMs into a pattern of localized deposition? It is expected that answering these questions would require 3-D models, while present models are based on peeling-ballooning stability with 1-D models for plasma profiles. A similar set of complicating factors can be identified for other instabilities. Alfven eigenmodes in ITER are expected to be driven primarily by the energetic alphas, but MeV neutral beam injection of up to 33 MW raises the issue of synergistic effects (e.g., loss of NB fast ions from AEs driven by fast alphas), and non-linear interaction among a 'sea' of many high-n potentially unstable modes expected from ITER's large size. Instabilities that are weakened by the strong toroidal rotation (e.g. turbulence or resistive wall modes) in present NB-heated machines may be more robust under the much weaker external torque provided by ITER's high energy beams. A better understanding of extrinsic rotation driven largely by conditions at

Analysis and Design of Symmetrical Capacitor Diode Voltage Multiplier Driven by LCL-T Resonant Converter

Science.gov (United States)

Malviya, Devesh; Borage, Mangesh Balkrishna; Tiwari, Sunil

2017-12-01

This paper investigates the possibility of application of Resonant Immittance Converters (RICs) as a current source for the current-fed symmetrical Capacitor-Diode Voltage Multiplier (CDVM) with LCL-T Resonant Converter (RC) as an example. Firstly, detailed characterization of the current-fed symmetrical CDVM is carried out using repeated simulations followed by the normalization of the simulation results in order to derive the closed-form curve fit equations to predict the operating modes, output voltage and ripple in terms of operating parameters. RICs, due to their ability to convert voltage source into a current source, become a possible candidate for the realization of current source for the current-fed symmetrical CDVM. Detailed analysis, optimization and design of LCL-T RC with CDVM is performed in this paper. A step by step design procedure for the design of CDVM and the converter is proposed. A 5-stage prototype symmetrical CDVM driven by LCL-T RC to produce 2.5 kV, 50 mA dc output voltage is designed, built and tested to validate the findings of the analysis and simulation.

Plasma based accelerators

Energy Technology Data Exchange (ETDEWEB)

Caldwell, Allen [Max-Planck-Institut fuer Physik, Muenchen (Germany)

2015-05-01

The concept of laser-induced plasma wakefields as a technique to accelerate charged particles was introduced 35 years ago as a means to go beyond the accelerating gradients possible with metallic cavities supporting radio frequency electromagnetic fields. Significant developments in laser technology have made possible the pulse intensity needed to realize this concept, and rapid progress is now underway in the realization of laser-driven plasma wakefield acceleration. It has also been realized that similar accelerating gradients can be produced by particle beams propagating in plasmas, and experimental programs have also been undertaken to study this possibility. Positive results have been achieved with electron-driven plasma wakefields, and a demonstration experiment with proton-driven wakefields is under construction at CERN. The concepts behind these different schemes and their pros and cons are described, as well as the experimental results achieved. An outlook for future practical uses of plasma based accelerators will also be given.

A Burke-Schumann Analysis of Dual-Flame Structure Supported by a Burning Droplet

Science.gov (United States)

Nayagam, V.; Dietrich, D.; Williams, F. A.

2016-01-01

Droplet combustion experiments carried out onboard the International Space Station (ISS), using pure fuels and fuel mixtures, have shown that quasi-steady burning can be sustained by a non-traditional flame configuration, namely a "cool flame" burning in the "partial-burning" regime where both fuel and oxygen leak through the low-temperature controlled flame-sheet. Recent experiments involving large, bi-component fuel (n-decane and hexanol, 50/50 by volume) droplets at elevated pressures show that the visible, hot flame becomes extremely weak while the burning rate remains relatively high, suggesting the possibility of simultaneous presence of "cool" and "hot" flames of roughly equal importance. The radiant output from these bi-component droplets is relatively high and cannot be accounted for only by the presence of a visible hot-flame. In this analysis we explore the theoretical possibility of a dual-flame structure, where one flame lies close to the droplet surface called the "cool-flame," and other farther away from the droplet surface, termed the "hot-flame." A Burke-Schumann analysis of this dual-structure seems to indicate such flame structures are possible over a narrow range of initial conditions. Theoretical results can be compared against available experimental data for pure and bi-component fuel droplet combustion to test how realistic the model may be.

Diagnostics of microwave assisted electron cyclotron resonance plasma source for surface modification of nylon 6

Science.gov (United States)

More, Supriya E.; Das, Partha Sarathi; Bansode, Avinash; Dhamale, Gayatri; Ghorui, S.; Bhoraskar, S. V.; Sahasrabudhe, S. N.; Mathe, Vikas L.

2018-01-01

Looking at the increasing scope of plasma processing of materials surface, here we present the development and diagnostics of a microwave assisted Electron Cyclotron Resonance (ECR) plasma system suitable for surface modification of polymers. Prior to the surface-treatment, a detailed diagnostic mapping of the plasma parameters throughout the reactor chamber was carried out by using single and double Langmuir probe measurements in Ar plasma. Conventional analysis of I-V curves as well as the elucidation form of the Electron Energy Distribution Function (EEDF) has become the source of calibration of plasma parameters in the reaction chamber. The high energy tail in the EEDF of electron temperature is seen to extend beyond 60 eV, at much larger distances from the ECR zone. This proves the suitability of the rector for plasma processing, since the electron energy is much beyond the threshold energy of bond breaking in most of the polymers. Nylon 6 is used as a representative candidate for surface processing in the presence of Ar, H2 + N2, and O2 plasma, treated at different locations inside the plasma chamber. In a typical case, the work of adhesion is seen to almost get doubled when treated with oxygen plasma. Morphology of the plasma treated surface and its hydrophilicity are discussed in view of the variation in electron density and electron temperature at these locations. Nano-protrusions arising from plasma treatment are set to be responsible for the hydrophobicity. Chemical sputtering and physical sputtering are seen to influence the surface morphology on account of sufficient electron energies and increased plasma potential.

A high-voltage equipment (high voltage supply, high voltage pulse generators, resonant charging inductance, synchro-instruments for gyrotron frequency measurements) for plasma applications

International Nuclear Information System (INIS)

Spassov, Velin

1996-01-01

This document reports my activities as visitor-professor at the Gyrotron Project - INPE Plasma Laboratory. The main objective of my activities was designing, construction and testing a suitable high-voltage pulse generator for plasma applications, and efforts were concentrated on the following points: Design of high-voltage resonant power supply with tunable output (0 - 50 kV) for line-type high voltage pulse generator; design of line-type pulse generator (4 microseconds pulse duration, 0 - 25 kV tunable voltage) for non linear loads such as a gyrotron and P III reactor; design of resonant charging inductance for resonant line-type pulse generator, and design of high resolution synchro instrument for gyrotron frequency measurement. (author)

Radiation yield from SHIVA Star plasma flow switch driven fast liner implosions

International Nuclear Information System (INIS)

Degnan, J.H.; Baker, W.L.; Beason, J.D.

1987-01-01

A 2.5 Terawatt 0.5 MJ isotropic equivalent radiation yield was obtained in a SHIVA Star plasma flow switch driven fast liner implosion. The 1313 μF 80 kV discharge delivered 13 MA to a coaxial vacuum inductive store with a plasma armature. Over 9.4 MA current was plasma flow switched to the implosion load (>90% of the gun muzzle current at that time). The load wa a 5 cm radius, 2 cm tall, 200 μg/cm/sup 2/ aluminum plated Formvar cylindrical foil. The radiation pulse was measured with an array of seven X-ray diodes (XRDs). The XRDs all had aluminum photocathodes, a variety of filters and nickel mesh to reduce the incident X-ray photon flux to avoid Child-Langmuir saturation. The filters were chosen so that the authors had seven different diode response functions covering the energy range from 15 eV to about 3 keV. The filters were mounted remote (about 30 cm) from the XRDs. The anode mesh served as part of the mesh array. The distance between meshes was greater than 10 cm. Each XRD had a 5 cm diameter cathode with an aperture limited to a 2 cm diameter. The XRD anode-cathode gap was 1 cm and the bias was 5 kV. The theoretical Child-Langmuir saturation signal was 125 V with 50 Ω termination. The maximum observed signal was 75 V

Characterization of aluminum x-pinch plasmas driven by the 0.5 TW Lion accelerator

International Nuclear Information System (INIS)

Qi, N.; Hammer, D.A.; Kalantantar, D.H.; Noonan, W.A.; Rondeau, G.; Workman, J.B.; Richardson, M.C.

1989-01-01

The x-pinch, obtained by crossing two fine wires at one or more points as the load for the 0.5 TW Lion accelerator, has been used as a bright x-ray source. High density and temperature hot spots are observed at the crossing point(s). From these hot spots, an intense, spatially confined burst of x-rays is emitted which can serve as a pump for resonant photo-pumping lasers. The authors present experimental results concerning the radiation emission using Al x-pinches. The optimum mass loading for different ionization stages of Al ions and the total x-ray energy yields are examined. The density and temperature of the plasma and the size of the hot spots are measures. Based upon the results of these experiments, the authors evaluate resonant photopumping schemes such as those involving Be-like ions, using the Al x-pinch emission as the pump source

Parametric instabilities in large plasmas

International Nuclear Information System (INIS)

Brambilla, Marco; Liberman, Bernardo.

1979-01-01

Parametric decay processes in large plasmas are considered as the linear stage of a three wave interaction (pump, sideband and beat wave) in which the amplitude of the externally excited pump is sufficiently large to neglect pump depletion to first order, yet sufficiently small to allow a linearized treatment of the pump propagation to zeroth order. The coupling coefficients are then obtained from an iterative solution of Vlasov equation, and a compact expression is derived, in which the multiple series over Bessel functions is explicitly summed. Even in the limit of a very long wavelength pump, the dispersion relation obtained in this way does not coincide with the one obtained using the well-known ''dipole'' approximation, unless both the sideband and beat wave are resonant modes of the plasma. An analysis of the origin of this discrepancy allows us to conclude that ''quasimodes'' (evanescent waves driven absolutely unstable by the pump) are more correctly described by the iterative approach

Acceleration of laser-injected electron beams in an electron-beam driven plasma wakefield accelerator

International Nuclear Information System (INIS)

Knetsch, Alexander

2018-03-01

Plasma wakefields deliver accelerating fields that are approximately a 100 times higher than those in conventional radiofrequency or even superconducting radiofrequency cavities. This opens a transformative path towards novel, compact and potentially ubiquitous accelerators. These prospects, and the increasing demand for electron accelerator beamtime for various applications in natural, material and life sciences, motivate the research and development on novel plasma-based accelerator concepts. However, these electron beam sources need to be understood and controlled. The focus of this thesis is on electron beam-driven plasma wakefield acceleration (PWFA) and the controlled injection and acceleration of secondary electron bunches in the accelerating wake fields by means of a short-pulse near-infrared laser. Two laser-triggered injection methods are explored. The first one is the Trojan Horse Injection, which relies on very good alignment and timing control between electron beam and laser pulse and then promises electron bunches with hitherto unprecedented quality as regards emittance and brightness. The physics of electron injection in the Trojan Horse case is explored with a focus on the final longitudinal bunch length. Then a theoretical and numerical study is presented that examines the physics of Trojan Horse injection when performed in an expanding wake generated by a smooth density down-ramp. The benefits are radically decreased drive-electron bunch requirements and a unique bunch-length control that enables longitudinal electron-bunch shaping. The second laser-triggered injection method is the Plasma Torch Injection, which is a versatile, all-optical laser-plasma-based method capable to realize tunable density downramp injection. At the SLAC National Laboratory, the first proof-of-principle was achieved both for Trojan Horse and Plasma Torch injection. Setup details and results are reported in the experimental part of the thesis along with the commissioning

Micromechanical Resonator Driven by Radiation Pressure Force.

Science.gov (United States)

Boales, Joseph A; Mateen, Farrukh; Mohanty, Pritiraj

2017-11-22

Radiation pressure exerted by light on any surface is the pressure generated by the momentum of impinging photons. The associated force - fundamentally, a quantum mechanical aspect of light - is usually too small to be useful, except in large-scale problems in astronomy and astrodynamics. In atomic and molecular optics, radiation pressure can be used to trap or cool atoms and ions. Use of radiation pressure on larger objects such as micromechanical resonators has been so far limited to its coupling to an acoustic mode, sideband cooling, or levitation of microscopic objects. In this Letter, we demonstrate direct actuation of a radio-frequency micromechanical plate-type resonator by the radiation pressure force generated by a standard laser diode at room temperature. Using two independent methods, the magnitude of the resonator's response to forcing by radiation pressure is found to be proportional to the intensity of the incident light.

An Experimental Study of Continuous Plasma Flows Driven by a Confined Arc in a Transverse Magnetic Field

Science.gov (United States)

Barger, R. L.; Brooks, J. D.; Beasley, W. D.

1961-01-01

A crossed-field, continuous-flow plasma accelerator has been built and operated. The highest measured velocity of the flow, which was driven by the interaction of the electric and magnetic fields, was about 500 meters per second. Some of the problems discussed are ion slip, stability and uniformity of the discharge, effect of the magnetic field on electron emission, use of preionization, and electrode contamination.

CENTER FOR PULSED POWER DRIVEN HIGH ENERGY DENSITY PLASMA STUDIES

Energy Technology Data Exchange (ETDEWEB)

Professor Bruce R. Kusse; Professor David A. Hammer

2007-04-18

This annual report summarizes the activities of the Cornell Center for Pulsed-Power-Driven High-Energy-Density Plasma Studies, for the 12-month period October 1, 2005-September 30, 2006. This period corresponds to the first year of the two-year extension (awarded in October, 2005) to the original 3-year NNSA/DOE Cooperative Agreement with Cornell, DE-FC03-02NA00057. As such, the period covered in this report also corresponds to the fourth year of the (now) 5-year term of the Cooperative Agreement. The participants, in addition to Cornell University, include Imperial College, London (IC), the University of Nevada, Reno (UNR), the University of Rochester (UR), the Weizmann Institute of Science (WSI), and the P.N. Lebedev Physical Institute (LPI), Moscow. A listing of all faculty, technical staff and students, both graduate and undergraduate, who participated in Center research activities during the year in question is given in Appendix A.

Stochastic resonance is applied to quantitative analysis for weak chromatographic signal of glyburide in plasma

International Nuclear Information System (INIS)

Zhang Wei; Xiang Bingren; Wu Yanwei; Shang Erxin

2005-01-01

Based on the theory of stochastic resonance, a new method carried on the quantitive analysis to weak chromatographic signal of glyburide in plasma, which was embedded in the noise background and the signal-to-noise ratio (SNR) of HPLC-UV is enhanced remarkably. This method enhances the quantification limit to 1 ng ml -1 , which is the same as HPLC-MS, and makes it possible to detect the weak signal accurately by HPLC-UV, which was not suitable before. The results showed good recovery and linear range from 1 to 50 ng ml -1 of glyburide in plasma and the method can be used for quantitative analysis of glyburide

Half bridge resonant converter for ignition of thermal plasmas; Convertidor resonante de medio puente para la ignicion de plasmas termicos

Energy Technology Data Exchange (ETDEWEB)

Pena E, L

1998-12-31

In this work the background, design, implementation and performance of a half bridge resonant converter (HBRC) used as an electronic ignition system for arc plasma torch generation is presented. The significance of the design lies in its simplicity, versatility and low cost. The system operates like a high voltage supply attached to electrodes before gaseous breakdown and like open circuit when electric arc is established. Resonant converter is implemented with a high voltage and high speed power driver intended for control the power MOSFET transistors connected in half bridge topology with L C load. The HBRC operates besides interference into domestic electric supply line (120 V, 60 Hz) as well electric measurement devices. Advantages and limitations of the converter are reviewed. Experimental impedance variation in the medium as a function of frequency operation and some experiences in striking arcs are also presented. (Author).

One-dimensional full wave treatment of mode conversion process at the ion-ion hybrid resonance in a bounded tokamak plasma

International Nuclear Information System (INIS)

Monakhov, I.; Becoulet, A.; Fraboulet, D.; NGuyen, F.

1998-09-01

A consistent picture of the mode conversion (MC) process at the ion-ion hybrid resonance in a bounded plasma of a tokamak is discussed, which clarifies the role of the global fast wave interference and cavity effects in the determination of the MC efficiency. This picture is supported by simulations with one-dimensional full wave kinetic code 'VICE'. The concept of the 'global resonator', formed by the R = n 2 || boundary cutoffs [B. Saoutic et al., Phys. Rev. Lett. 76, 1647 (1996)], is justified, as well as the importance of a proper tunneling factor choice η cr = 0.22 [A. K. Ram et al., Phys. Plasmas 3, 1976 (1996)]. The MC scheme behavior appears to be very sensitive to the MC layer position relative to the global wave field pattern, i.e. to the local value of 'poloidal' electric field at the resonance. Optimal MC regimes are found to be attainable without requirement of a particular parallel wavenumber choice. (author)

Curvature driven instabilities in toroidal plasmas

International Nuclear Information System (INIS)

Andersson, P.

1986-11-01

The electromagnetic ballooning mode, the curvature driven trapped electron mode and the toroidally induced ion temperature gradient mode have been studies. Eigenvalue equations have been derived and solved both numerically and analytically. For electromagnetic ballooning modes the effects of convective damping, finite Larmor radius, higher order curvature terms, and temperature gradients have been investigated. A fully toroidal fluid ion model has been developed. It is shown that a necessary and sufficient condition for an instability below the MHD limit is the presence of an ion temperature gradient. Analytical dispersion relations giving results in good agreement with numerical solutions are also presented. The curvature driven trapped electron modes are found to be unstable for virtually all parameters with growth rates of the order of the diamagnetic drift frequency. Studies have been made, using both a gyrokinetic ion description and the fully toroidal ion model. Both analytical and numerical results are presented and are found to be in good agreement. The toroidally induced ion temperature gradients modes are found to have a behavior similar to that of the curvature driven trapped electron modes and can in the electrostatic limit be described by a simple quadratic dispersion equation. (author)

Stabilization of sawteeth with third harmonic deuterium ICRF-accelerated beam in JET plasmas

Energy Technology Data Exchange (ETDEWEB)

Girardo, Jean-Baptiste [EUROfusion Consortium, JET, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France); Sharapov, Sergei; Fitzgerald, Michael; Hawkes, Nick; Kiptily, Vasily; Lupelli, Ivan [CCFE, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Boom, Jurrian [Max-Planck-Institut für Plasmaphysik, 85748 Garching (Germany); Dumont, Rémi; Garbet, Xavier; Sarazin, Yanick; Schneider, Mireille [CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France); Eriksson, Jacob [Department of Physics and Astronomy, Uppsala University, 751 20 Uppsala (Sweden); Mantsinen, Mervi [Catalan Institution for Research and Advanced Studies, 08010 Barcelona (Spain); Barcelona Supercomputing Center, 08034 Barcelona (Spain)

2016-01-15

Sawtooth stabilisation by fast ions is investigated in deuterium (D) and D-helium 3 (He3) plasmas of JET heated by deuterium Neutral Beam Injection combined in synergy with Ion Cyclotron Resonance Heating (ICRH) applied on-axis at 3rd beam cyclotron harmonic. A very significant increase in the sawtooth period is observed, caused by the ICRH-acceleration of the beam ions born at 100 keV to the MeV energy range. Four representative sawteeth from four different discharges are compared with Porcelli's model. In two discharges, the sawtooth crash appears to be triggered by core-localized Toroidal Alfvén Eigenmodes inside the q = 1 surface (also called “tornado” modes) which expel the fast ions from within the q = 1 surface, over time scales comparable with the sawtooth period. Two other discharges did not exhibit fast ion-driven instabilities in the plasma core, and no degradation of fast ion confinement was found in both modelling and direct measurements of fast ion profile with the neutron camera. The developed sawtooth scenario without fast ion-driven instabilities in the plasma core is of high interest for the burning plasmas. Possible causes of the sawtooth crashes on JET are discussed.

Hybrid simulations of radial transport driven by the Rayleigh-Taylor instability

Science.gov (United States)

Delamere, P. A.; Stauffer, B. H.; Ma, X.

2017-12-01

Plasma transport in the rapidly rotating giant magnetospheres is thought to involve a centrifugally-driven flux tube interchange instability, similar to the Rayleigh-Taylor (RT) instability. In three dimensions, the convective flow patterns associated with the RT instability can produce strong guide field reconnection, allowing plasma mass to move radially outward while conserving magnetic flux (Ma et al., 2016). We present a set of hybrid (kinetic ion / fluid electron) plasma simulations of the RT instability using high plasma beta conditions appropriate for Jupiter's inner and middle magnetosphere. A density gradient, combined with a centrifugal force, provide appropriate RT onset conditions. Pressure balance is achieved by initializing two ion populations: one with fixed temperature, but varying density, and the other with fixed density, but a temperature gradient that offsets the density gradient from the first population and the centrifugal force (effective gravity). We first analyze two-dimensional results for the plane perpendicular to the magnetic field by comparing growth rates as a function of wave vector following Huba et al. (1998). Prescribed perpendicular wave modes are seeded with an initial velocity perturbation. We then extend the model to three dimensions, introducing a stabilizing parallel wave vector. Boundary conditions in the parallel direction prohibit motion of the magnetic field line footprints to model the eigenmodes of the magnetodisc's resonant cavity. We again compare growth rates based on perpendicular wave number, but also on the parallel extent of the resonant cavity, which fixes the size of the largest parallel wavelength. Finally, we search for evidence of strong guide field magnetic reconnection within the domain by identifying areas with large parallel electric fields or changes in magnetic field topology.

Plasma control and utilization

International Nuclear Information System (INIS)

Ensley, D.L.

1976-01-01

A plasma is confined and heated by a microwave field resonant in a cavity excited in a combination of the TE and TM modes while responding to the resonant frequency of the cavity as the plasma dimensions change to maintain operation at resonance. The microwave field is elliptically or circularly polarized as to prevent the electromagnetic confining field from going to zero. A high Q chamber having superconductive walls is employed to minimize wall losses while providing for extraction of thermonuclear energy produced by fusion of nuclei in the plasma. 24 claims, 15 figures

Propagation of electromagnetic waves in the plasma near electron cyclotron resonance: Undulator-induced transparency

International Nuclear Information System (INIS)

Shvets, G.; Tushentsov, M.; Tokman, M.D.; Kryachko, A.

2005-01-01

Propagation of electromagnetic waves in magnetized plasma near the electron cyclotron frequency can be strongly modified by adding a weak magnetic undulator. For example, both right- and left-hand circularly polarized waves can propagate along the magnetic field without experiencing resonant absorption. This effect of entirely eliminating electron cyclotron heating is referred to as the undulator-induced transparency (UIT) of the plasma, and is the classical equivalent of the well-known quantum mechanical effect of electromagnetically induced transparency. The basics of UIT are reviewed, and various ways in which UIT can be utilized to achieve exotic propagation properties of electromagnetic waves in plasmas are discussed. For example, UIT can dramatically slow down the waves' group velocity, resulting in the extreme compression of the wave energy in the plasma. Compressed waves are polarized along the propagation direction, and can be used for synchronous electron or ion acceleration. Strong coupling between the two wave helicities are explored to impart the waves with high group velocities ∂ω/∂k for vanishing wave numbers k. Cross-helicity coupling for realistic density and magnetic field profiles are examined using a linearized fluid code, particle-in-cell simulations, and ray-tracing WKB calculations

Energy and momentum balance in nonlinear interactions of resonant and nonresonant waves in turbulent plasmas

International Nuclear Information System (INIS)

Vladimirov, S.V.; Nambu, Mitsuhiro

1995-01-01

From investigations of resonant interactions of particles and waves in turbulent plasmas it is well known that not only resonant particles contribute to expressions for the wave energy and momentum providing conservation of these quantities for closed systems. In particular, it was demonstrated that contribution of the nonresonant particles is very important for the energy conservation in the quasilinear theory: although the nonresonant terms do not appear in the diffusion equation, they contribute to the wave energy (and, in general, wave momentum) ensuring the conservation of total energy (and momentum) in the system. We note that the real part of the dielectric permittivity ε ωk as well as the wave frequency ω k of the resonant waves do not depend on time in the quasilinear approximation since only nonresonant particles (which distribution is constant) contribute to them. The resonant wave amplitude, however, is the function on time, and changing of the wave energy is completely balanced by the corresponding change of the resonant particle energy. If in the system there are only nonresonant waves, and it is closed (i.e., there is no energy exchange with some external sources or sinks), the system is stationary and the nonresonant wave as well as particle energy are not changing

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