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Sample records for high frequency plasma

  1. High-frequency plasma oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Akhiezer, A I; Fainberg, Y B; Sitenko, A G; Stepanov, K; Kurilko, V; Gorbatenko, M; Kirochkin, U [Academy of Sciences of the Ukrainian SSR (USSR)

    1958-07-01

    It is well known that the electrical conductivity of a plasma, the ion-electron equilibration time, and the time required to heat the electron component of the plasma all increase greatly with increasing temperature. Consequently, the usual method of Joule heating a plasma may be difficult to apply in the region of high temperatures (> 10{sup 6}K), especially if the plasma current alone, without any additional measures, is used to generate magnetic fields for the confinement of the plasma. Therefore, it is of interest to study methods of plasma heating that do not directly use Joule heat, especially methods by which energy is directly supplied to the ion component during the time between collisions. Some of these methods make use of ionic resonance as well as other resonance phenomena which can occur in plasma in an external magnetic field. This paper deals with certain aspects of the theory of high-frequency plasma oscillations.

  2. High-frequency conductivity of photoionized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Anakhov, M. V.; Uryupin, S. A., E-mail: uryupin@sci.lebedev.ru [National Research Nuclear University “MEPhI,” (Russian Federation)

    2016-08-15

    The tensor of the high-frequency conductivity of a plasma created via tunnel ionization of atoms in the field of linearly or circularly polarized radiation is derived. It is shown that the real part of the conductivity tensor is highly anisotropic. In the case of a toroidal velocity distribution of photoelectrons, the possibility of amplification of a weak high-frequency field polarized at a sufficiently large angle to the anisotropy axis of the initial nonequilibrium distribution is revealed.

  3. HIGH FREQUENCY ELECTROSTATIC INSTABILITIES IN A PLASMA

    Energy Technology Data Exchange (ETDEWEB)

    Klein, M W; Auer, P L

    1963-06-15

    The dispersion relation is examined for a collisionless infinite plasma in the presence of an anisotropic Maxwellian velocity distribution and a uniform external magnetic field. Unstable solutions exist below the muitiples of the electron cyclotron frequency provided the temperature anisotropy is sufficiently large. The dependence of the growth rate upon harmonic number, density, angle of propagation with respect to the magnetic field, and frequency is discussed for zero as well as non-zero parallel temperatures. In the latter case, the waves are strongly damped as their frequency approaches a multiple of the gyro- frequency. (auth)

  4. Sheath impedance effects in very high frequency plasma experiments

    International Nuclear Information System (INIS)

    Schwarzenbach, W.; Howling, A.A.; Fivaz, M.; Brunner, S.; Hollenstein, C.

    1995-05-01

    The frequency dependence (13.56 MHz to 70 MHz) of the ion energy distribution at the ground electrode was measured by mass spectrometry in a symmetrical capacitive argon discharge. Reduced sheath impedance at Very High Frequency allows high levels of plasma power and substrate ion flux whilst maintaining low levels of ion energy and electrode voltage. The lower limit of ion bombardment energy is fixed by the sheath floating potential at high frequency, in contrast to low frequencies where only the rf voltage amplitude is determinant. The capacitive sheaths are thinner at high frequencies which accentuates the high frequency reduction in sheath impedance. It is argued that the frequency dependence of sheath impedance is responsible for the principal characteristics of Very High Frequency plasmas. The measurements are summarised by simple physical descriptions and compared with a Particle-In-Cell simulation. (author) figs., tabs., refs

  5. Anomalous high-frequency resistivity of a plasma

    International Nuclear Information System (INIS)

    Kruer, W.L.; Dawson, J.M.

    1971-06-01

    In one- and two-dimensional computer simulations we investigate anomalous high-frequency resistivity in a plasma driven by a large electric field oscillating near the electron plasma frequency. The large field excites the oscillating two-stream and the ion-acoustic decay instabilities in agreement with the linear theory. When the ion and electron fluctuations saturate, a strong anomalous heating of the plasma sets in. This strong heating is due to an efficient coupling of the externally imposed large electric field to the plasma by ion fluctuations. We determine the anomalous collision frequency and the saturation fluctuation amplitudes as a function of the external field amplitude and frequency, and the electron-ion mass ratio. A simple nonlinear theory gives results in reasonable agreement with simulations. 24 refs., 10 figs

  6. Propagation of high frequency electrostatic surface waves along the planar interface between plasma and dusty plasma

    Science.gov (United States)

    Mishra, Rinku; Dey, M.

    2018-04-01

    An analytical model is developed that explains the propagation of a high frequency electrostatic surface wave along the interface of a plasma system where semi-infinite electron-ion plasma is interfaced with semi-infinite dusty plasma. The model emphasizes that the source of such high frequency waves is inherent in the presence of ion acoustic and dust ion acoustic/dust acoustic volume waves in electron-ion plasma and dusty plasma region. Wave dispersion relation is obtained for two distinct cases and the role of plasma parameters on wave dispersion is analyzed in short and long wavelength limits. The normalized surface wave frequency is seen to grow linearly for lower wave number but becomes constant for higher wave numbers in both the cases. It is observed that the normalized frequency depends on ion plasma frequencies when dust oscillation frequency is neglected.

  7. High-frequency heating of plasma with two ion species

    International Nuclear Information System (INIS)

    Klima, R.; Longinov, A.V.; Stepanov, K.N.

    1975-01-01

    The authors consider the penetration of electromagnetic waves with a frequency of the order of the ion cyclotron frequencies and with a fixed longitudinal wave number ksub(long), so that Nsub(long)=ksub(long)c/ω>>1 deep into an inhomogeneous plasma with two ion species. The propagation of two kinds of waves (fast and slow) with widely differing polarization and transverse refraction index is possible. For both types of waves there is an evanescence region at the plasma periphery. The evanescence region is narrow for slow waves and they easily penetrate the plasma. In a dense plasma they become electrostatic and can reach the ion-ion hybrid resonance region. However, the damping of these waves due to Cherenkov interaction with electrons in a high-temperature plasma is strong and therefore they are not suitable for heating plasma of large dimensions, as they are absorbed at the plasma periphery. The fast waves have a wider evanescence region and can be excited effectively only if N 2 is not too high. These waves can be completely absorbed in the plasma (due to Cherenkov interaction with electrons) if xi approximately (v 2 sub(Ti)/v 2 sub(A))Zsub(e)(ωsub(pi)a/c)exp(-Zsub(e) 2 ) > 1, where a is the plasma radius and Zsub(e) = ω/(√2 ksub(long)vsub(Te)). Fast waves can also reach the region where they are transformed into slow waves. In this region their damping increases considerably. It is shown that the transformation region in an inhomogeneous plasma with two ion species in a non-uniform magnetic field may be at the centre of the plasma. Fast waves can be used effectively for heating plasma of large dimensions. (author)

  8. Thermal history of the plasma and high-frequency gravitons

    CERN Document Server

    Giovannini, Massimo

    2009-01-01

    Possible deviations from a radiation-dominated evolution, occurring prior the synthesis of light nuclei, impacted on the spectral energy density of high-frequency gravitons. For a systematic scrutiny of this situation, the $\\Lambda$CDM paradigm must be complemented by (at least two) physical parameters describing, respectively, a threshold frequency and a slope. The supplementary frequency scale sets the lower border of a high-frequency domain where the spectral energy grows with a slope which depends, predominantly, upon the total sound speed of the plasma right after inflation. While the infra-red region of the graviton energy spectrum is nearly scale-invariant, the expected signals for typical frequencies larger than 0.01 nHz are hereby analyzed in a model-independent framework by requiring that the total sound speed of the post-inflationary plasma is smaller than the speed of light. Current (e.g. low-frequency) upper limits on the tensor power spectra (determined from the combined analysis of the three la...

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

    International Nuclear Information System (INIS)

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

    2017-01-01

    Plasma discharge is a novel disinfection and effectual inactivation approach to treat microorganisms in aqueous systems. Inactivation of Gram-negative Escherichia coli (E. coli) by generating high-frequency, high-voltage, oxygen (O_2) injected and hydrogen peroxide (H_2O_2) added discharge in water was achieved. The effect of H_2O_2 dose and oxygen injection rate on electrical characteristics of discharge and E. coli disinfection has been reported. Microbial log reduction dependent on H_2O_2 addition with O_2 injection was observed. The time variation of the inactivation efficiency quantified by the log reduction of the initial E. coli population on the basis of optical density measurement was reported. The analysis of emission spectrum recorded after discharge occurrence illustrated the formation of oxidant species (OH"•, H, and O). Interestingly, the results demonstrated that O_2 injected and H_2O_2 added, underwater plasma discharge had fabulous impact on the E. coli sterilization. The oxygen injection notably reduced the voltage needed for generating breakdown in flowing water and escalated the power of discharge pulses. No impact of hydrogen peroxide addition on breakdown voltage was observed. A significant role of oxidant species in bacterial inactivation also has been identified. Furthermore the E. coli survivability in plasma treated water with oxygen injection and hydrogen peroxide addition drastically reduced to zero. The time course study also showed that the retardant effect on E. coli colony multiplication in plasma treated water was favorable, observed after long time. High-frequency underwater plasma discharge based biological applications is technically relevant and would act as baseline data for the development of novel antibacterial processing strategies.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, M. W.; Choi, S.; Lyakhov, K.; Shaislamov, U. [Jeju National University, Department of Nuclear and Energy Engineering (Korea, Republic of); Mongre, R. K.; Jeong, D. K. [Jeju National University, Faculty of Biotechnology (Korea, Republic of); Suresh, R.; Lee, H. J., E-mail: hjlee@jejunu.ac.kr [Jeju National University, Department of Nuclear and Energy Engineering (Korea, Republic of)

    2017-03-15

    Plasma discharge is a novel disinfection and effectual inactivation approach to treat microorganisms in aqueous systems. Inactivation of Gram-negative Escherichia coli (E. coli) by generating high-frequency, high-voltage, oxygen (O{sub 2}) injected and hydrogen peroxide (H{sub 2}O{sub 2}) added discharge in water was achieved. The effect of H{sub 2}O{sub 2} dose and oxygen injection rate on electrical characteristics of discharge and E. coli disinfection has been reported. Microbial log reduction dependent on H{sub 2}O{sub 2} addition with O{sub 2} injection was observed. The time variation of the inactivation efficiency quantified by the log reduction of the initial E. coli population on the basis of optical density measurement was reported. The analysis of emission spectrum recorded after discharge occurrence illustrated the formation of oxidant species (OH{sup •}, H, and O). Interestingly, the results demonstrated that O{sub 2} injected and H{sub 2}O{sub 2} added, underwater plasma discharge had fabulous impact on the E. coli sterilization. The oxygen injection notably reduced the voltage needed for generating breakdown in flowing water and escalated the power of discharge pulses. No impact of hydrogen peroxide addition on breakdown voltage was observed. A significant role of oxidant species in bacterial inactivation also has been identified. Furthermore the E. coli survivability in plasma treated water with oxygen injection and hydrogen peroxide addition drastically reduced to zero. The time course study also showed that the retardant effect on E. coli colony multiplication in plasma treated water was favorable, observed after long time. High-frequency underwater plasma discharge based biological applications is technically relevant and would act as baseline data for the development of novel antibacterial processing strategies.

  11. Direct excitation of a high frequency wave by a low frequency wave in a plasma

    International Nuclear Information System (INIS)

    Tanaka, Takayasu

    1993-01-01

    A new mechanism is presented of an excitation of a high frequency wave by a low frequency wave in a plasma. This mechanism works when the low frequency wave varies in time in a manner deviated from a usual periodic motion with a constant amplitude. The conversion rate is usually not large but the conversion is done without time delay after the variation of the low frequency wave. The Manley Rowe relation in the usual sense does not hold in this mechanism. This mechanism can excite also waves with same or lower frequencies. (author)

  12. High-frequency microinstabilities in hot-electron plasmas

    International Nuclear Information System (INIS)

    Chen, Y.J.; Nevins, W.M.; Smith, G.R.

    1981-01-01

    Instabilities with frequencies in the neighborhood of the electron cyclotron frequency are of interest in determining stable operating regimes of hot-electron plasmas in EBT devices and in tandem mirrors. Previous work used model distributions significantly different than those suggested by recent Fokker-Planck studies. We use much more realistic model distributions in a computer code that solves the full electromagnetic dispersion relation governing longitudinal and transverse waves in a uniform plasma. We allow for an arbitrary direction of wave propagation. Results for the whistler and upper-hybrid loss-cone instabilities are presented

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

    Science.gov (United States)

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

    2011-01-01

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

  14. High frequency electric field spikes formed by electron beam-plasma interaction in plasma density gradients

    International Nuclear Information System (INIS)

    Gunell, H.; Loefgren, T.

    1997-02-01

    In the electron beam-plasma interaction at an electric double layer the beam density is much higher than in the classical beam-plasma experiments. The wave propagation takes place along the density gradient, that is present at the high potential side of the double layer. Such a case is studied experimentally by injecting the electron beam from a plane cathode, without any grids suppressing the gradient, and by particle simulations. The high frequency field concentrates in a sharp 'spike' with a half width of the order of one wavelength. The spike is found to be a standing wave surrounded by regions dominated by propagating waves. It forms at a position where its frequency is close to the local plasma frequency. The spike forms also when the electric field is well below the threshold for modulational instability, and long before a density cavity is formed in the simulations. Particle simulations reveal that, at the spike, there is a backward travelling wave that, when it is strongly damped, accelerates electrons back towards the cathode. In a simulation of a homogeneous plasma without the density gradient no spike is seen, and the wave is purely travelling instead of standing. 9 refs

  15. High frequency parametric wave phenomena and plasma heating: a review

    International Nuclear Information System (INIS)

    Porkolab, M.

    1975-11-01

    A survey of parametric instabilities in plasma, and associated particle heating, is presented. A brief summary of linear theory is given. The physical mechanism of decay instability, the purely growing mode (oscillating two-stream instability) and soliton and density cavity formation is presented. Effects of density gradients are discussed. Possible nonlinear saturation mechanisms are pointed out. Experimental evidence for the existence of parametric instabilities in both unmagnetized and magnetized plasmas is reviewed in some detail. Experimental observation of plasma heating associated with the presence of parametric instabilities is demonstrated by a number of examples. Possible application of these phenomena to heating of pellets by lasers and heating of magnetically confined fusion plasmas by high power microwave sources is discussed

  16. Excitation of plasma waves by nonlinear currents induced by a high-frequency electromagnetic pulse

    Energy Technology Data Exchange (ETDEWEB)

    Grishkov, V. E.; Uryupin, S. A., E-mail: uryupin@sci.lebedev.ru [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2017-03-15

    Excitation of plasma waves by nonlinear currents induced by a high-frequency electromagnetic pulse is analyzed within the kinetic approach. It is shown that the most efficient source of plasma waves is the nonlinear current arising due to the gradient of the energy density of the high-frequency field. Generation of plasma waves by the drag current is usually less efficient but not negligibly small at relatively high frequencies of electron–ion collisions. The influence of electron collisions on the excitation of plasma waves by pulses of different duration is described quantitatively.

  17. Physics of Collisional Plasmas Introduction to High-Frequency Discharges

    CERN Document Server

    Moisan, Michel

    2012-01-01

    The Physics of Collisional Plasmas deals with the plasma physics of interest to laboratory research and industrial applications, such as lighting, fabrication of microelectronics, destruction of greenhouse gases. Its emphasis is on explaining the physical mechanisms, rather than the detailed mathematical description and theoretical analysis. At the introductory level, it is important to convey the characteristic physical phenomena of plasmas, before addressing the ultimate formalism of kinetic theory, with its microscopic, statistical mechanics approach. To this aim, this text translates the physical phenomena into more tractable equations, using the hydrodynamic model; this considers the plasma as a fluid, in which the macroscopic physical parameters are the statistical averages of the microscopic (individual) parameters. This book is an introduction to the physics of collisional plasmas, as opposed to plasmas in space. It is intended for graduate students in physics and engineering . The first chapter intr...

  18. Excitation of a plasma by high frequencies for illumination purposes

    International Nuclear Information System (INIS)

    Valdivia B, R.

    2003-01-01

    The power electronics plays a very important paper so much in the national as international industrial development. For that reason, many of the works are focused in the one analysis and amplification of this area with the purpose of finding improvements in the existent systems and always looking for oneself end: the energy saving. Moreover, in the last years has occurred great interest to other very important area given their properties of energy profit, novelty and mainly their wide range of applications. This area is the study and use of the plasma. Many institutions with international recognition already invest and they develop systems in these two big areas of the technology among those that is the National Institute of Nuclear Research (INlN) with some laboratories dedicated to the work of the plasma, one of them the Laboratory of Thermal Plasma Applications (LAPT). The conjugation of both areas was analysed and developed in the present work with the one purpose of designing a system to generate thermal plasma and to give him one or but applications like it is to produce a luminous source as like to degrade organic gases as the Methane or Acetylene. This was developed by means of a resonant inverter with the help of MOSFET IRFK2D450 transistors and a load L C in a serial-parallel configuration with the purpose to profit their condition of resonance to have the maximum transfer of energy to the plasma. For to have a best profit of the energy it was realized an analysis of design for to oblige to the transistors to commute in zero voltage (ZVS) and to avoid then lost of power of C A. (Author)

  19. Kinetic theory of interaction of high frequency waves with a rotating plasma

    International Nuclear Information System (INIS)

    Chiu, S. C.; Chan, V. S.; Chu, M. S.; Lin-Liu, Y. R.

    2000-01-01

    The equations of motion of charged particles of a strongly magnetized flowing plasma under the influence of high frequency waves are derived in the guiding center approximation. A quasilinear theory of the interactions of waves with rotating plasmas is formulated. This is applied to investigate the effect of radio frequency waves on a rotating tokamak plasma with a heated minority species. The angular momentum drive is mainly due to the rf-induced radial minority current. The return current by the bulk plasma gives an equal and opposite rotation drive on the bulk. Using moment equations and a small banana width approximation, the JxB drive was evaluated for the bulk plasma. Quite remarkably, although collisions are included, the net rotation drive is due to a term which can be obtained by neglecting collisions. (c) 2000 American Institute of Physics

  20. Dynamic characteristics of non-ideal plasmas in an external high frequency electric field

    Energy Technology Data Exchange (ETDEWEB)

    Adamyan, V M [Department of Theoretical Physics, I. I. Mechnikov Odessa National University, 65026 Odessa (Ukraine); Djuric, Z [Silvaco Data System, Silvaco Technology Centre, Compass Point, St. Ives PE27 5JL (United Kingdom); Mihajlov, A A [Institute of Physics, PO Box 57, 11001 Belgrade (Serbia and Montenegro); Sakan, N M [Institute of Physics, PO Box 57, 11001 Belgrade (Serbia and Montenegro); Tkachenko, I M [Department of Applied Mathematics, ETSII, Polytechnic University of Valencia, Camino de Vera s/n, Valencia 46022 (Spain)

    2004-07-21

    The dynamic electric conductivity, dielectric permeability and refraction and reflection coefficients of a completely ionized gaseous plasma in a high frequency (HF) external electric field are calculated. These results are obtained within the self-consistent field approach developed earlier for the static conductivity determination. The plasma electron density, N{sub e}, and temperature, T, varied within the following limits: 10{sup 19} {<=} N{sub e} {<=} 10{sup 21} cm{sup -3} and 2 x 10{sup 4} {<=} T {<=} 10{sup 6} K, respectively. The external electric field frequency, f, varied in the range 3 GHz{<=} f {<=} 0.05{omicron}{sub p}, where {omicron}{sub p} is the circular plasma frequency. Thus, the upper limit for f is either in the microwave or in the far infrared frequency band. The final results are shown in a parameterized form, suitable for laboratory applications.

  1. Dynamic characteristics of non-ideal plasmas in an external high frequency electric field

    International Nuclear Information System (INIS)

    Adamyan, V M; Djuric, Z; Mihajlov, A A; Sakan, N M; Tkachenko, I M

    2004-01-01

    The dynamic electric conductivity, dielectric permeability and refraction and reflection coefficients of a completely ionized gaseous plasma in a high frequency (HF) external electric field are calculated. These results are obtained within the self-consistent field approach developed earlier for the static conductivity determination. The plasma electron density, N e , and temperature, T, varied within the following limits: 10 19 ≤ N e ≤ 10 21 cm -3 and 2 x 10 4 ≤ T ≤ 10 6 K, respectively. The external electric field frequency, f, varied in the range 3 GHz≤ f ≤ 0.05ο p , where ο p is the circular plasma frequency. Thus, the upper limit for f is either in the microwave or in the far infrared frequency band. The final results are shown in a parameterized form, suitable for laboratory applications

  2. Power absorption of high-frequency electromagnetic waves in a partially ionized magnetized plasma

    International Nuclear Information System (INIS)

    Guo Bin; Wang Xiaogang

    2005-01-01

    Power absorption of high-frequency electromagnetic waves in a uniformly magnetized plasma layer covering a highly conducting surface is studied under atmosphere conditions. It is assumed that the system consists of not only electrons and positive ions but negative ions as well. By a general formula derived in our previous work [B. Guo and X. G. Wang, Plasma Sci. Tech. 7, 2645 (2005)], the total power absorption in the plasma layer with multiple reflections between an air-plasma interface and the conducting surface is computed. The results show that although the existence of negative ions greatly reduces the total power absorption, the magnetization of the plasma can, however, partially enhance it. Parameter dependence of the effects is calculated and discussed

  3. Experimental observation of the inductive electric field and related plasma nonuniformity in high frequency capacitive discharge

    International Nuclear Information System (INIS)

    Ahn, S. K.; Chang, H. Y.

    2008-01-01

    To elucidate plasma nonuniformity in high frequency capacitive discharges, Langmuir probe and B-dot probe measurements were carried out in the radial direction in a cylindrical capacitive discharge driven at 90 MHz with argon pressures of 50 and 400 mTorr. Through the measurements, a significant inductive electric field (i.e., time-varying magnetic field) was observed at the radial edge, and it was found that the inductive electric field creates strong plasma nonuniformity at high pressure operation. The plasma nonuniformity at high pressure operation is physically similar to the E-H mode transition typically observed in inductive discharges. This result agrees well with the theories of electromagnetic effects in large area and/or high frequency capacitive discharges

  4. The thermal history of the plasma and high-frequency gravitons

    International Nuclear Information System (INIS)

    Giovannini, Massimo

    2009-01-01

    Possible deviations from a radiation-dominated evolution, occurring prior to the synthesis of light nuclei, impacted on the spectral energy density of high-frequency gravitons. For a systematic scrutiny of this situation, the ΛCDM paradigm must be complemented by (at least two) physical parameters describing, respectively, a threshold frequency and a slope. The supplementary frequency scale sets the lower border of a high-frequency domain where the spectral energy grows with a slope which depends, predominantly, upon the total sound speed of the plasma right after inflation. While the infrared region of the graviton energy spectrum is nearly scale invariant, the expected signals for typical frequencies larger than 0.01 nHz are hereby analyzed in a model-independent framework by requiring that the total sound speed of the post-inflationary plasma be smaller than the speed of light. Current (e.g., low-frequency) upper limits on the tensor power spectra (determined from the combined analysis of the three large-scale data sets) are shown to be compatible with a detectable signal in the frequency range of wideband interferometers. In the present context, the scrutiny of the early evolution of the sound speed of the plasma can then be mapped onto a reliable strategy of parameter extraction including not only the well-established cosmological observables but also the forthcoming data from wideband interferometers.

  5. Simulation of cold plasma in a chamber under high- and low-frequency voltage conditions for a capacitively coupled plasma

    Institute of Scientific and Technical Information of China (English)

    Hao Daoxin; Cheng Jia; Ji Linhong; Sun Yuchun

    2012-01-01

    The characteristics of cold plasma,especially for a dual-frequency capacitively coupled plasma (CCP),play an important role for plasma enhanced chemical vapor deposition,which stimulates further studies using different methods.In this paper,a 2D fluid model was constructed for N2 gas plasma simulations with CFD-ACE+,a commercial multi-physical software package.First,the distributions of electric potential (Epot),electron number density (Ne),N number density (N) and electron temperature (Te) are described under the condition of high frequency (HF),13.56 MHz,HF voltage,300 V,and low-frequency (LF) voltage,0 V,particularly in the sheath.Based on this,the influence of HF on Ne is further discussed under different HF voltages of 200 V,300 V,400 V,separately,along with the influence of LF,0.3 MHz,and various LF voltages of 500 V,600 V,700 V.The results show that sheaths of about 3 mm are formed near the two electrodes,in which Epot and Te vary extensively with time and space,while in the plasma bulk Epot changes synchronously with an electric potential of about 70 V and Te varies only in a small range.N is also modulated by the radio frequency,but the relative change in N is small.Ne varies only in the sheath,while in the bulk it is steady at different time steps.So,by comparing Ne in the plasma bulk at the steady state,we can see that Ne will increase when HF voltage increases.Yet,Ne will slightly decrease with the increase of LF voltage.At the same time,the homogeneity will change in both x and y directions.So both HF and LF voltages should be carefully considered in order to obtain a high-density,homogeneous plasma.

  6. Study of dense-plasma properties using very high-frequency electromagnetic waves (light waves)

    International Nuclear Information System (INIS)

    Gormezano, C.

    1966-06-01

    A study is made of methods based on the use of lasers for measuring the electronic density and temperature of dense plasmas (N e > 10 15 e/cm 3 ): - an interferometric method using a gas laser, based on the. properties of the Perot-Fabry cavities; - a method making use of the 90 deg C scattering produced by the plasma on light emitted by a ruby laser. These methods have been applied to various dense plasmas: - high-frequency plasma torch; - azimuth compression; - plasma bursts produced by focussing a laser beam on a metal target. The measurements have also been carried out using conventional methods of diagnosis. It has thus been possible to measure densities of between 5.10 15 and 10 19 e/cm 3 and temperatures of between 3 and 10 eV. These different-methods are then compared, (author) [fr

  7. Absorption of high-frequency electromagnetic energy in a high-temperature plasma

    Energy Technology Data Exchange (ETDEWEB)

    Sagdeyev, R S; Shafranov, V D

    1958-07-01

    In this paper an analysis of the cyclotron and Cherenkov mechanisms is given. These are two fundamental mechanisms for noncollisional absorption of electromagnetic radiation by plasma in a magnetic field. The expressions for the dielectric permeability tensor, for plasma with a nonisotropic temperature distribution in a magnetic field, are obtained by integrating the kinetic equation with Lagrangian particle co-ordinates in a form suitable to allow a comprehensive physical interpretation of the absorption mechanisms. The oscillations of a plasma column stabilized by a longitudinal field have been analyzed. For uniform plasma, the frequency spectrum has been obtained together with the direction of electromagnetic wave propagation when both the cyclotron and Cherenkov absorption mechanisms take place. The influence of nonlinear effects on the electromagnetic wave absorption and the part which cyclotron and Cherenkov absorption play in plasma heating have also been investigated.

  8. Experimental studies on the high-frequency heating of a plasma in the frequency range of the ion cyclotron harmonics

    International Nuclear Information System (INIS)

    Laeuter, R.

    1976-05-01

    Experiments on the HF heating of a plasma in a cylindrical arrangement with pump frequencies ω 0 in the ion cyclotron harmonics nωsub(ci) are described. A magnetized plasma of relativily high density (approximately 10 14 cm -3 ) is generated in a pinch-like source with pulsated gas inlet, and said plasma then expands along diverging magnetic-field lines in a quasi-static homogeneous guide field B 0 = 330 G. This results in a practically fully ionized, low-impurity and more or less homogeneous plasma column of a diameter of approximately 20 cm at a variable density between 5 x 10 11 and 5 x 10 12 cm -3 and at electron temperatures of 5 to 8 eV. A standing magneto-hydrodynamic wave is excited in this plasma by means of a 1.8 m Stix coil which is part of the anode resonant circuit of a pulsated 1 MHz 500-kW transmitter. The axial wavelength is lambdasub(z) = 45 cm, the pulse duration amounts to tau = 200 μs. The degree of modulation B tilde/B 0 of the quasi-static magnetic field by the HF field is adjustable and ranges between 0.015 and 0.06. The heating at 2ωsub(ci) and 4ωsub(ci) is investigated within this study. Efficiency measurements show that a very effective energy transfer to the plasma occurs with both frequencies. Ion temperatures between 70 and 100 eV are ascertained by means of a retarding-potential spectrometer. For plasma heating, similar turbulent mechanisms seem to be responsible in both cases whereas the linear wave-particle resonance at 2ωsub(ci) seems to be of subordinated importance. The theoretically assumed parametric decay into ion-Bernstein waves, which should be possible at 4 ωsub(ci), is not observed. Measurements with compensated magnetic loops and electrostatic probes make a disturbance of the radial plasma confinement obvious, by which an anormally high pulse frequency might be explained. (orig.) [de

  9. Three-dimensional propagation and absorption of high frequency Gaussian beams in magnetoactive plasmas

    International Nuclear Information System (INIS)

    Nowak, S.; Orefice, A.

    1994-01-01

    In today's high frequency systems employed for plasma diagnostics, power heating, and current drive the behavior of the wave beams is appreciably affected by the self-diffraction phenomena due to their narrow collimation. In the present article the three-dimensional propagation of Gaussian beams in inhomogeneous and anisotropic media is analyzed, starting from a properly formulated dispersion relation. Particular attention is paid, in the case of electromagnetic electron cyclotron (EC) waves, to the toroidal geometry characterizing tokamak plasmas, to the power density evolution on the advancing wave fronts, and to the absorption features occurring when a beam crosses an EC resonant layer

  10. Green frequency-doubled laser-beam propagation in high-temperature hohlraum plasmas.

    Science.gov (United States)

    Niemann, C; Berger, R L; Divol, L; Froula, D H; Jones, O; Kirkwood, R K; Meezan, N; Moody, J D; Ross, J; Sorce, C; Suter, L J; Glenzer, S H

    2008-02-01

    We demonstrate propagation and small backscatter losses of a frequency-doubled (2omega) laser beam interacting with inertial confinement fusion hohlraum plasmas. The electron temperature of 3.3 keV, approximately a factor of 2 higher than achieved in previous experiments with open geometry targets, approaches plasma conditions of high-fusion yield hohlraums. In this new temperature regime, we measure 2omega laser-beam transmission approaching 80% with simultaneous backscattering losses of less than 10%. These findings suggest that good laser coupling into fusion hohlraums using 2omega light is possible.

  11. System constitution of plasma high frequency heating device and element equipment

    International Nuclear Information System (INIS)

    Nagashima, Takashi

    1988-01-01

    On the high frequency heating device used for nuclear fusion experiment, the system constitution and the main items of development for the element equipment are described. As for the high frequency heating device, large technical progress was observed in the past 10 years as the second stage heating for tokamaks and one of the main means of current drive. At present, three frequency zones are regarded as promising for plasma high frequency heating in large nuclear fusion devices, and the experiment of 10 MW class is in progress at JT-60, JET and so on. There are electron cyclotron heating, lower hybrid resonance frequency heating and ion cyclotron range of frquency heating. The basic constitution of these heating devices includes a high frequency source, a transmission system, a connection system, and a common system for control, cooling, record and others. The ECH device using gyrotrons of several tens GHz, the LHRF heating device using large power klystrons up to several GHz and the ICRF heating device up to 200 MHz are briefly explained. The main element equipments composing the high frequency heating systems of several tens MW are discussed. (Kako, I.)

  12. High-frequency gyrotrons and their application to tokamak plasma heating

    International Nuclear Information System (INIS)

    Kreischer, K.E.

    1981-01-01

    A comprehensive analysis of high frequency (100 to 200 GHz) and high power (> 100 kW) gyrotrons has been conducted. It is shown that high frequencies will be required in order for electron cyclotron radiation to propagate to the center of a compact tokamak power reactor. High power levels will be needed in order to ignite the plasma with a reasonable number of gyrotron units. In the first part of this research, a set of analytic expressions, valid for all TE cavity modes and all harmonics, is derived for the starting current and frequency detuning using the Vlasov-Maxwell equations in the weakly relativistic limit. The use of an optical cavity is also investigated

  13. Multi-fluid Approach to High-frequency Waves in Plasmas. III. Nonlinear Regime and Plasma Heating

    Science.gov (United States)

    Martínez-Gómez, David; Soler, Roberto; Terradas, Jaume

    2018-03-01

    The multi-fluid modeling of high-frequency waves in partially ionized plasmas has shown that the behavior of magnetohydrodynamic waves in the linear regime is heavily influenced by the collisional interaction between the different species that form the plasma. Here, we go beyond linear theory and study large-amplitude waves in partially ionized plasmas using a nonlinear multi-fluid code. It is known that in fully ionized plasmas, nonlinear Alfvén waves generate density and pressure perturbations. Those nonlinear effects are more pronounced for standing oscillations than for propagating waves. By means of numerical simulations and analytical approximations, we examine how the collisional interaction between ions and neutrals affects the nonlinear evolution. The friction due to collisions dissipates a fraction of the wave energy, which is transformed into heat and consequently raises the temperature of the plasma. As an application, we investigate frictional heating in a plasma with physical conditions akin to those in a quiescent solar prominence.

  14. A Stark-tuned, far-infrared laser for high frequency plasma diagnostics

    International Nuclear Information System (INIS)

    Mansfield, D.K.; Vocaturo, M.; Guttadora, L.; Rockmore, M.; Micai, K.; Krug, P.A.

    1992-03-01

    A Stark-tuned optically pumped far-infrared methanol laser operating at 119 micrometers has been built. The laser is designed to operate at high power while exhibiting a well-separated Stark doublet. At a pump power of 65 Watts and electric field of 1 kV/cm the laser has delivered over 100 mW c.w. while exhibiting a frequency splitting of 34 MHz. These parameters indicate that this laser would be suitable for use in the present generation of modulated interferometers on large thermonuclear plasma devices. The achieved modulation frequency is more than an order of magnitude higher than could be achieved using standard techniques

  15. Novel high-frequency energy-efficient pulsed-dc generator for capacitively coupled plasma discharge

    Science.gov (United States)

    Mamun, Md Abdullah Al; Furuta, Hiroshi; Hatta, Akimitsu

    2018-03-01

    The circuit design, assembly, and operating tests of a high-frequency and high-voltage (HV) pulsed dc generator (PDG) for capacitively coupled plasma (CCP) discharge inside a vacuum chamber are reported. For capacitive loads, it is challenging to obtain sharp rectangular pulses with fast rising and falling edges, requiring intense current for quick charging and discharging. The requirement of intense current generally limits the pulse operation frequency. In this study, we present a new type of PDG consisting of a pair of half-resonant converters and a constant current-controller circuit connected with HV solid-state power switches that can deliver almost rectangular high voltage pulses with fast rising and falling edges for CCP discharge. A prototype of the PDG is assembled to modulate from a high-voltage direct current (HVdc) input into a pulsed HVdc output, while following an input pulse signal and a set current level. The pulse rise time and fall time are less than 500 ns and 800 ns, respectively, and the minimum pulse width is 1 µs. The maximum voltage for a negative pulse is 1000 V, and the maximum repetition frequency is 500 kHz. During the pulse on time, the plasma discharge current is controlled steadily at the set value. The half-resonant converters in the PDG perform recovery of the remaining energy from the capacitive load at every termination of pulse discharge. The PDG performed with a high energy efficiency of 85% from the HVdc input to the pulsed dc output at a repetition rate of 1 kHz and with stable plasma operation in various discharge conditions. The results suggest that the developed PDG can be considered to be more efficient for plasma processing by CCP.

  16. Novel high-frequency energy-efficient pulsed-dc generator for capacitively coupled plasma discharge.

    Science.gov (United States)

    Mamun, Md Abdullah Al; Furuta, Hiroshi; Hatta, Akimitsu

    2018-03-01

    The circuit design, assembly, and operating tests of a high-frequency and high-voltage (HV) pulsed dc generator (PDG) for capacitively coupled plasma (CCP) discharge inside a vacuum chamber are reported. For capacitive loads, it is challenging to obtain sharp rectangular pulses with fast rising and falling edges, requiring intense current for quick charging and discharging. The requirement of intense current generally limits the pulse operation frequency. In this study, we present a new type of PDG consisting of a pair of half-resonant converters and a constant current-controller circuit connected with HV solid-state power switches that can deliver almost rectangular high voltage pulses with fast rising and falling edges for CCP discharge. A prototype of the PDG is assembled to modulate from a high-voltage direct current (HVdc) input into a pulsed HVdc output, while following an input pulse signal and a set current level. The pulse rise time and fall time are less than 500 ns and 800 ns, respectively, and the minimum pulse width is 1 µs. The maximum voltage for a negative pulse is 1000 V, and the maximum repetition frequency is 500 kHz. During the pulse on time, the plasma discharge current is controlled steadily at the set value. The half-resonant converters in the PDG perform recovery of the remaining energy from the capacitive load at every termination of pulse discharge. The PDG performed with a high energy efficiency of 85% from the HVdc input to the pulsed dc output at a repetition rate of 1 kHz and with stable plasma operation in various discharge conditions. The results suggest that the developed PDG can be considered to be more efficient for plasma processing by CCP.

  17. The concept of a plasma centrifuge with a high frequency rotating magnetic field and axial circulation

    Science.gov (United States)

    Borisevich, V. D.; Potanin, E. P.

    2017-07-01

    The possibility of using a rotating magnetic field (RMF) in a plasma centrifuge (PC), with axial circulation to multiply the radial separation effect in an axial direction, is considered. For the first time, a traveling magnetic field (TMF) is proposed to drive an axial circulation flow in a PC. The longitudinal separation effect is calculated for a notional model, using specified operational parameters and the properties of a plasma, comprising an isotopic mixture of 20Ne-22Ne and generated by a high frequency discharge. The optimal intensity of a circulation flow, in which the longitudinal separation effect reaches its maximum value, is studied. The optimal parameters of the RMF and TMF for effective separation, as well as the centrifuge performance, are calculated.

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

    International Nuclear Information System (INIS)

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

    2001-01-01

    This article presents an experimental demonstration of a high-pressure unconditionally stable nonequilibrium molecular plasma sustained by a combination of a continuous wave CO laser and a sub-breakdown radio frequency (rf) electric field. The plasma is sustained in a CO/N 2 mixture containing trace amounts of NO or O 2 at pressures of P=0.4 - 1.2atm. The initial ionization of the gases is produced by an associative ionization mechanism in collisions of two CO molecules excited to high vibrational levels by resonance absorption of the CO laser radiation with subsequent vibration-vibration (V-V) pumping. Further vibrational excitation of both CO and N 2 is produced by free electrons heated by the applied rf field, which in turn produces additional ionization of these species by the associative ionization mechanism. In the present experiments, the reduced electric field, E/N, is sufficiently low to preclude field-induced electron impact ionization. Unconditional stability of the resultant cold molecular plasma is enabled by the negative feedback between gas heating and the associative ionization rate. Trace amounts of nitric oxide or oxygen added to the baseline CO/N 2 gas mixture considerably reduce the electron - ion dissociative recombination rate and thereby significantly increase the initial electron density. This allows triggering of the rf power coupling to the vibrational energy modes of the gas mixture. Vibrational level populations of CO and N 2 are monitored by infrared emission spectroscopy and spontaneous Raman spectroscopy. The experiments demonstrate that the use of a sub-breakdown rf field in addition to the CO laser allows an increase of the plasma volume by about an order of magnitude. Also, CO infrared emission spectra show that with the rf voltage turned on the number of vibrationally excited CO molecules along the line of sight increase by a factor of 3 - 7. Finally, spontaneous Raman spectra of N 2 show that with the rf voltage the vibrational

  19. Determination of trace amounts of boron in steel by high frequency plasma torch spectrometry

    International Nuclear Information System (INIS)

    Akiyoshi, Takanori; Tsukamoto, Takako

    1978-01-01

    Trace amount of boron in steel were determined by means of emission spectrometry using high frequency plasma torch. The sensitivity of this method depended on the kind of solvent used, and methyl alcohol gave the best sensitivity. The determination limit of boron in methanol was 0.002 μg/ml. The established method utilized the high sensibility of the plasma torch and the easy distillation of boron in methanol as trimethyl-borate (B(OCH 3 ) 3 ). The sample was dissolved by acids and dehydrated by hot H 2 SO 4 and H 3 Po 4 . After cooling and addition of methanol (60 ml), the solution was distilled to obtain 40 ml of the distillate. The amount of boron in the distillate was determined by the intensity of the spectral line of B 2497.73 A excited by plasma torch. This method was rapid and accurate, particularly in determining trace amounts of boron and the determination range of boron in steel was 0.2 to 150 ppm. This method was also appliciable to stainless steels and other alloys. (auth.)

  20. Oscillations and Stability of Plasma in an External High-Frequency Electric Field

    International Nuclear Information System (INIS)

    Aliev, Ju.M.; Gorbunov, L.M.; Silin, V.P.; Uotson, H.

    1966-01-01

    A theory is developed for the oscillations and stability of plasma in a strong external HF electric field. The kinetic equation with self-congruent reciprocity is linearized for weak deviations from the ground state. Since the latter depends on an external HF field, the linearized equation obtained has coefficients with a periodic time dependence. From this equation and also from Maxwell's equations there is derived a dispersion equation for plasma oscillations that represents the zero value of the infinite order determinant, and that is solved both for external field frequencies considerably exceeding the electron Langmuir frequency and for frequencies that are less. The external HF field changes the oscillation branches in a plasma without an external field, and also leads to a new low-frequency oscillation branch. Movement of particles in the HF field gives spatial dispersion. If the frequency of the field exceeds the election Langmuir frequency, the plasma oscillations are stable. At frequencies less than this level there occurs a build-up of low-frequency oscillations. Here the maximum of the build-up occurs when the external field frequencies approach the electron Langmuir frequency and is equal to the product of the Langmuir frequency and the one-third power of the electron-ion mass ratio. Away from the resonance, -the increment of build-up has the same order of magnitude as the ion Langmuir frequency. An external magnetic field increases the number of possible natural plasma oscillations and thereby increases the possibility of resonance with the external HF field. Allowance for the thermal motion of the particles enables one to determine the attenuation of the oscillations in question. Expressions for the decrements are derived. The effect of the external HF field on a plasma in which there are beams is also discussed. An HF field has a destabilizing effect on a system of this kind, since on the one hand there can be a build-up of fresh, low-frequency

  1. Improvements to a high-frequency fiber-optic system for plasma diagnostics

    International Nuclear Information System (INIS)

    Ogle, J.W.; Lyons, P.B.; Looney, L.; Hocker, L.; Nelson, M.A.; Zagarino, P.A.; Davies, T.J.; Simmons, R.D.; Selk, R.; Hopkins, B.

    1981-01-01

    A system for high-frequency recording of plasma diagnostics has previously been reported. Substantial improvements have been made in the system response, dynamic range, and calibration of the system. Plastic-clad silica fiber is used as a radiation-to-light converter using the Cerenkov process. A spectral equalizer device is used to compensate for the material dispersion in the fiber, increasing the frequency response (approx. = 1 GHz-km) and the dynamic range (a factor of > 20 over a FWHM 1 nm, 50% transmitting interference filter). The calibration system uses a pulsed injection laser diode (< 100 ps FWHM) injected into the fiber at the radiation end of the fiber and detected by a microchannel plate photomultiplier tube on the recording end. The injection laser diode is triggered by a synchronous trigger delay unit, which also triggers a sampling or real time scope after as much as 10 μs delay with < 50 ps jitter. The system improvements are described in detail and the utility of these components in other plasma diagnostic systems is discussed

  2. Radio-frequency wave excitation and damping on a high β plasma column

    International Nuclear Information System (INIS)

    Meuth, H.

    1984-01-01

    Azimuthally symmetric (m = 0) radio-frequency (RF) waves for zero and for finite axial wave number k/sub z/ are investigated on the High BETA Q Machine, a two-meter, 20 cm-diameter, low-compression linear theta pinch (T greater than or equal to 200 eV, n approx. = 10 15 cm -3 ) fast rising (0.4 μs) compression field. The (k/sub z/ = 0) modes occur spontaneously following the implosion phase of the discharge. A novel 100-MW 1 to 1.3 MHz, short wavelength current drive excites the plasma column in the vicinity of the lowest fast magnetoacoustic mode at various filling pressures. This current drive is designed as an integral part of the compression coil, which is segmented with a 20-cm axial wavelength (k/sub z/ = 0.314 cm -1 ). The electron density oscillations along major and minor chords at various positions are measured by interferometry perpendicular to the pinch axis. The oscillatory radial magnetic field component between pinch wall and hot plasma edge is measured by probes. Phases, amplitudes and radial mode structure are studied for the free (k = 0) modes and the externally driven (k does not equal 0) modes for various filling pressures of deuterium. The energy deposition from the externally driven RF wave leads to a radial expansion of the plasma column, as observed by axial interferometry and by excluded flux measurements

  3. High-frequency coherent edge fluctuations in a high-pedestal-pressure quiescent H-mode plasma.

    Science.gov (United States)

    Yan, Z; McKee, G R; Groebner, R J; Snyder, P B; Osborne, T H; Burrell, K H

    2011-07-29

    A set of high frequency coherent (HFC) modes (f=80-250 kHz) is observed with beam emission spectroscopy measurements of density fluctuations in the pedestal of a strongly shaped quiescent H-mode plasma on DIII-D, with characteristics predicted for kinetic ballooning modes (KBM): propagation in the ion-diamagnetic drift direction; a frequency near 0.2-0.3 times the ion-diamagnetic frequency; inferred toroidal mode numbers of n∼10-25; poloidal wave numbers of k(θ)∼0.17-0.4 cm(-1); and high measured decorrelation rates (τ(c)(-1)∼ω(s)∼0.5×10(6) s(-1)). Their appearance correlates with saturation of the pedestal pressure. © 2011 American Physical Society

  4. High-frequency emissions during the propagation of an electron beam in a high-density plasma

    International Nuclear Information System (INIS)

    Lalita and Tripathi, V.K.

    1988-01-01

    A relativistic annular electron beam passing through a high-density plasma excites Langmuir waves via Cerenkov interaction. The Langmuir waves are backscattered off ions via nonlinear ion Landau damping. At moderately high amplitudes these waves are parametrically up-converted by the beam into high-frequency electromagnetic radiation, as observed in some recent experiments. A nonlocal theory of this process is developed in a cylindrical geometry. It is seen that the growth rate of the Langmuir wave scales as one-third power of beam density. The growth rate of parametric instability scales as one-fourth power of beam density and the square root of beam thickness

  5. Ultrafine TaC powders prepared in a high frequency plasma

    International Nuclear Information System (INIS)

    Canteloup, J.; Mocellin, A.

    1976-01-01

    Ultrafine tantalum carbide powders were prepared under conditions allowing higher purities to be achieved than when plasma or chemical vapour deposition techniques are used. The process consists of dissociation-vaporisation of powders in a radio frequency argon plasma followed by quenching of the vapours and collection in an electrostatic precipitator. Physical and chemical properties are given. The presence of excess carbon appears to protect against oxidation and as a dispersing medium for the carbide powders. (U.K.)

  6. MULTI-FLUID APPROACH TO HIGH-FREQUENCY WAVES IN PLASMAS. I. SMALL-AMPLITUDE REGIME IN FULLY IONIZED MEDIUM

    Energy Technology Data Exchange (ETDEWEB)

    Martínez-Gómez, David; Soler, Roberto; Terradas, Jaume, E-mail: david.martinez@uib.es [Departament de Física, Universitat de les Illes Balears, E-07122, Palma de Mallorca (Spain)

    2016-12-01

    Ideal magnetohydrodynamics (MHD) provides an accurate description of low-frequency Alfvén waves in fully ionized plasmas. However, higher-frequency waves in many plasmas of the solar atmosphere cannot be correctly described by ideal MHD and a more accurate model is required. Here, we study the properties of small-amplitude incompressible perturbations in both the low- and the high-frequency ranges in plasmas composed of several ionized species. We use a multi-fluid approach and take into account the effects of collisions between ions and the inclusion of Hall’s term in the induction equation. Through the analysis of the corresponding dispersion relations and numerical simulations, we check that at high frequencies ions of different species are not as strongly coupled as in the low-frequency limit. Hence, they cannot be treated as a single fluid. In addition, elastic collisions between the distinct ionized species are not negligible for high-frequency waves, since an appreciable damping is obtained. Furthermore, Coulomb collisions between ions remove the cyclotron resonances and the strict cutoff regions, which are present when collisions are not taken into account. The implications of these results for the modeling of high-frequency waves in solar plasmas are discussed.

  7. TOPICAL REVIEW: Electromagnetic effects in high-frequency capacitive discharges used for plasma processing

    Science.gov (United States)

    Chabert, P.

    2007-02-01

    In plasma processing, capacitive discharges have classically been operated in the electrostatic regime, for which the excitation wavelength λ is much greater than the electrode radius, and the plasma skin depth δ is much greater than the electrode spacing. However, contemporary reactors are larger and excited at higher frequencies which leads to strong electromagnetic effects. This paper gives a review of the work that has recently been carried out to carefully model and diagnose these effects, which cause major uniformity problems in plasma processing for microelectronics and flat panel displays industries.

  8. Electromagnetic effects in high-frequency capacitive discharges used for plasma processing

    International Nuclear Information System (INIS)

    Chabert, P

    2007-01-01

    In plasma processing, capacitive discharges have classically been operated in the electrostatic regime, for which the excitation wavelength λ is much greater than the electrode radius, and the plasma skin depth δ is much greater than the electrode spacing. However, contemporary reactors are larger and excited at higher frequencies which leads to strong electromagnetic effects. This paper gives a review of the work that has recently been carried out to carefully model and diagnose these effects, which cause major uniformity problems in plasma processing for microelectronics and flat panel displays industries. (topical review)

  9. High frequency fishbone driven by passing energetic ions in tokamak plasmas

    Science.gov (United States)

    Wang, Feng; Yu, L. M.; Fu, G. Y.; Shen, Wei

    2017-05-01

    High frequency fishbone instability driven by passing energetic ions was first reported in the Princeton beta experiment with tangential neutral-beam-injection (Heidbrink et al 1986 Phys. Rev. Lett. 57 835-8). It could play an important role for ITER-like burning plasmas, where α particles are mostly passing particles. In this work, a generalized energetic ion distribution function and finite drift orbit width effect are considered to improve the theoretical model for passing particle driving fishbone instability. For purely passing energetic ions with zero drift orbit width, the kinetic energy δ {{W}k} is derived analytically. The derived analytic expression is more accurate as compared to the result of previous work (Wang 2001 Phys. Rev. Lett. 86 5286-8). For a generalized energetic ion distribution function, the fishbone dispersion relation is derived and is solved numerically. Numerical results show that broad and off-axis beam density profiles can significantly increase the beam ion beta threshold {βc} for instability and decrease mode frequency.

  10. Frequency up-conversion and spectral breaking of a high power microwave pulse propagation in a self-generated plasma

    International Nuclear Information System (INIS)

    Kuo, S.P.; Ren, A.

    1993-01-01

    The main concern of the propagation of high power microwave pulse is the energy loss of the pulse before reaching the destination. The loss is caused by self-generated plasma. There are two processes which are responsible for the energy loss (so called tail erosion). They are collisional damping and cutoff reflection. In very high power region, the cutoff reflection is much more severe than the collisional damping. A frequency up-conversion process may help to avoid the cutoff reflection of powerful electromagnetic pulse propagating in a self-generated plasma. Both chamber experiments and numerical simulation are performed. When the field amplitude only slightly exceeds the breakdown threshold field of the background gas, the result shows that the carrier frequency ω of the pulse shifts upward during the growth of local plasma frequency ωpe 2 . Thus, the self-generated plasma remains underdense to the pulse. However, the spectrum of the pulse starts to break up into two major peaks when the amplitude of the pulse is further increased. The frequency of one of the peaks is lower than the original carrier frequency and that of the other peak is higher than the original carrier frequency. These phenomena are observed both experimentally and numerically. The frequency down shift result is believed to be caused by damping mechanisms. Good agreement between the experimental results and the numerical simulation is obtained

  11. Hot pressing of nanocrystalline tantalum using high frequency induction heating and pulse plasma sintering

    Science.gov (United States)

    Jakubowicz, J.; Adamek, G.; Sopata, M.; Koper, J. K.; Siwak, P.

    2017-12-01

    The paper presents the results of nanocrystalline powder tantalum consolidation using hot pressing. The authors used two different heating techniques during hot pressing: high-frequency induction heating (HFIH) and pulse plasma sintering (PPS). A comparison of the structure, microstructure, mechanical properties and corrosion resistance of the bulk nanocrystalline tantalum obtained in both techniques was performed. The nanocrystalline powder was made to start from the microcrystalline one using the high-energy ball milling process. The nanocrystalline powder was hot-pressed at 1000 °C, whereas, for comparison, the microcrystalline powder was hot pressed up to 1500 °C for proper consolidation. The authors found that during hot pressing, the powder partially reacts with the graphite die covered by boron nitride, which facilitated punches and powder displacement in the die during densification. Tantalum carbide and boride in the nanocrystalline material was found, which can improve the mechanical properties. The hardness of the HFIH and PPS nanocrystalline tantalum was as high as 625 and 615 HV, respectively. The microstructure was more uniform in the PPS nanomaterial. The corrosion resistance in both cases deteriorated, in comparison to the microcrystalline material, while the PPS material corrosion resistance was slightly better than that of the HFIH one.

  12. Two new planar coil designs for a high pressure radio frequency plasma source

    Science.gov (United States)

    Munsat, T.; Hooke, W. M.; Bozeman, S. P.; Washburn, S.

    1995-04-01

    Two planar coil designs for a high pressure rf plasma source are investigated using spectroscopic techniques and circuit analysis. In an Ar plasma a truncated version of the commonly used ``spiral'' coil is found to produce improvements in peak electron density of 20% over the full version. A coil with figure-8 geometry is found to move plasma inhomogeneities off of center and produce electron densities comparable to the spiral coils. Both of these characteristics are advantageous in industrial applications. Coil design characteristics for favorable power coupling are also determined, including the necessity of closed hydrodynamic plasma loops and the drawback of closely situated antiparallel coil currents.

  13. Surface chemical structure of poly(ethylene naphthalate) films during degradation in low-pressure high-frequency plasma treatments

    Science.gov (United States)

    Kamata, Noritsugu; Yuji, Toshifumi; Thungsuk, Nuttee; Arunrungrusmi, Somchai; Chansri, Pakpoom; Kinoshita, Hiroyuki; Mungkung, Narong

    2018-06-01

    The surface chemical structure of poly(ethylene naphthalate) (PEN) films treated with a low-pressure, high-frequency plasma was investigated by storing in a box at room temperature to protect the PEN film surface from dust. The functional groups on the PEN film surface changed over time. The functional groups of –C=O, –COH, and –COOH were abundant in the Ar + O2 mixture gas plasma-treated PEN samples as compared with those in untreated PEN samples. The changes occurred rapidly after 2 d following the plasma treatment, reaching steady states 8 d after the treatment. Hydrophobicity had an inverse relationship with the concentration of these functional groups on the surface. Thus, the effect of the low-pressure high-frequency plasma treatment on PEN varies as a function of storage time. This means that radical oxygen and oxygen molecules are clearly generated in the plasma, and this is one index to confirm that radical reaction has definitely occurred between the gas and the PEN film surface with a low-pressure high-frequency plasma.

  14. Lithium line radiation in turbulent edge plasmas: Effects of low and high frequency temperature fluctuations

    Science.gov (United States)

    Rosato, J.; Capes, H.; Catoire, F.; Kadomtsev, M. B.; Levashova, M. G.; Lisitsa, V. S.; Marandet, Y.; Rosmej, F. B.; Stamm, R.

    2011-08-01

    In lithium-wall-conditioned tokamaks, the line radiation due to the intrinsic impurities (Li/Li+/Li++) plays a significant role on the power balance. Calculations of the radiation losses are usually performed using a stationary collisional-radiative model, assuming constant values for the plasma parameters (Ne, Te,…). Such an approach is not suitable for turbulent plasmas where the various parameters are time-dependent. This is critical especially for the edge region, where the fluctuation rates can reach several tens of percents [e.g. J.A. Boedo, J. Nucl. Mater. 390-391 (2009) 29-37]. In this work, the role of turbulence on the radiated power is investigated with a statistical formalism. A special emphasis is devoted to the role of temperature fluctuations, successively for low-frequency fluctuations and in the general case where the characteristic turbulence frequencies can be comparable to the collisional and radiative rates.

  15. Theoretical and Experimental Studies of High-Frequency Plasma Structures; Etudes Theoriques et Experimentales sur les Structures HF a Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Consoli, T. [CEA, Centre d' Etudes Nucleaires de Saclay (France)

    1969-03-15

    The author has studied high-frequency structures at the resonance {omega}{sub ec} = {omega}{sub HF} in an inhomogeneous magnetic field. The following points have been developed theoretically: the complete (relativistic and non-linear) analytical description of individual movement, taking into account the fact that the number of revolutions of the particles in the resonance zone is high; study of the self-consistent space charge field, with a view to establishing the conditions necessary for the energy of the ions to be of the order of the energy gained by the electrons in the resonance zone; calculation of the self-consistent HF field in the accelerated plasma, with a view to establishing the conditions for optimum operation of the HF accelerator; the problem of the mirror losses. The experimental results were obtained with various devices constructed for the purpose of verifying the theoretical predictions. With the Circe-Pleiade, where the ionization and acceleration functions have been separated by means of ionization with a Circe device ({lambda} = 3 cm, 300 W), it has been verified the relativistic law of variation of the parallel ion energy as a function of the injected density (existence of a minimum density for the entrainment of ions) and of the applied HF power (TE{sub 111} cavity, 3 GHz, 700 W). With the Circe accelerator ({lambda} =3 cm, P = 2.5kW, CW) it has been verified that, for n{sub plasma} n{sub c} , because of the strong attenuation of the field due to the high index. With the Icare device ({lambda} = 25 cm, P{sub HF} = 1 MW for 100 {mu}s), operating with pre-ionization by laser focalization on a solid D{sub 2} target with an injection density always higher than the cut-off density, accelerated deuteron

  16. Lithium line radiation in turbulent edge plasmas: Effects of low and high frequency temperature fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Rosato, J., E-mail: joel.rosato@univ-provence.fr [PIIM, UMR 6633, Universite de Provence/CNRS, Centre de St.-Jerome, Case 232, F-13397 Marseille Cedex 20 (France); Capes, H.; Catoire, F. [PIIM, UMR 6633, Universite de Provence/CNRS, Centre de St.-Jerome, Case 232, F-13397 Marseille Cedex 20 (France); Kadomtsev, M.B.; Levashova, M.G.; Lisitsa, V.S. [ITP, Russian Research Center ' Kurchatov Institute' , Moscow (Russian Federation); Marandet, Y. [PIIM, UMR 6633, Universite de Provence/CNRS, Centre de St.-Jerome, Case 232, F-13397 Marseille Cedex 20 (France); Rosmej, F.B. [LULI, UMR 7605, Universite Pierre et Marie Curie/CNRS, 4 Place Jussieu, Case 128, F-75252 Paris Cedex 05 (France); Stamm, R. [PIIM, UMR 6633, Universite de Provence/CNRS, Centre de St.-Jerome, Case 232, F-13397 Marseille Cedex 20 (France)

    2011-08-01

    In lithium-wall-conditioned tokamaks, the line radiation due to the intrinsic impurities (Li/Li{sup +}/Li{sup ++}) plays a significant role on the power balance. Calculations of the radiation losses are usually performed using a stationary collisional-radiative model, assuming constant values for the plasma parameters (N{sub e}, T{sub e},...). Such an approach is not suitable for turbulent plasmas where the various parameters are time-dependent. This is critical especially for the edge region, where the fluctuation rates can reach several tens of percents [e.g. J.A. Boedo, J. Nucl. Mater. 390-391 (2009) 29-37]. In this work, the role of turbulence on the radiated power is investigated with a statistical formalism. A special emphasis is devoted to the role of temperature fluctuations, successively for low-frequency fluctuations and in the general case where the characteristic turbulence frequencies can be comparable to the collisional and radiative rates.

  17. Radio frequency plasma excitation

    International Nuclear Information System (INIS)

    Burden, M.St.J.; Cross, K.B.

    1979-01-01

    An investigation into the use of rf sputtering for ion cleaning of insulating substrates before ion plating is reported. Initial experiments consisted of sputtering metals with rf power followed by the deposition of copper onto glass slides using rf plasma excitation and biasing supply. It was found that good quality films were obtained by rf ion plating onto plastics with excellent adhesion over a wide operating pressure range. A block schematic of the rf plasma excitation system is shown. (UK)

  18. Anomalous resistivity due to low-frequency turbulence. [of collisionless plasma with limited acceleration of high velocity runaway electrons

    Science.gov (United States)

    Rowland, H. L.; Palmadesso, P. J.

    1983-01-01

    Large amplitude ion cyclotron waves have been observed on auroral field lines. In the presence of an electric field parallel to the ambient magnetic field these waves prevent the acceleration of the bulk of the plasma electrons leading to the formation of a runaway tail. It is shown that low-frequency turbulence can also limit the acceleration of high-velocity runaway electrons via pitch angle scattering at the anomalous Doppler resonance.

  19. 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)

  20. High-frequency counter-flow plasma synthetic jet actuator and its application in suppression of supersonic flow separation

    Science.gov (United States)

    Wang, Hongyu; Li, Jun; Jin, Di; Tang, Mengxiao; Wu, Yun; Xiao, Lianghua

    2018-01-01

    We come up with a control strategy for suppression of supersonic flow separation based on high-frequency Counter-flow Plasma Synthetic Jet Actuator (CPSJA). The main purpose of this investigation is to verify if its control authority can be enhanced by the jet/shock interaction. We use a blunt nose to generate a bow shock, a step on a flat plate to introduce a massive separation in a Mach 2 wind tunnel, and the CPSJA to generate Plasma Synthetic Jet (PSJ). In this study, pulsed capacitive discharge is provided for an array of CPSJAs, which makes the actuation (discharge) frequency f1 = 1 kHz, f2 = 2 kHz and f3 = 3 kHz. We use the high-speed schlieren imaging and fast response pressure transducers as well as a numerical simulation to investigate the quiescent PSJ properties, the interaction between the jet and bow shock, and its disturbance effect on the downstream separated region. The schlieren images show that PSJ is characterized by a succession of vortex rings; the jet strength weakens with the increase of frequency. A 4.5 mN jet thrust is found for all the frequencies. The simulation results show that jet/shock interaction produces vorticity in the vortex ring of the jet, enhancing turbulent mixing in PSJ so that a great deal of momentum is produced into the flow. We found the downstream flow is significantly disturbed by the enhanced actuation. Actuation with frequency of f2, f3 which is close to the natural frequency fn of the separation bubble suppresses the separation with the upstream laminar boundary layer being periodically attenuated, which has a better control effect than f1. The control effect is sensitive to the position where PSJ interacts with the shear layer, but the amount of energy deposited in one pulse is not crucial in a separation reduction in the experiment.

  1. Study of dense-plasma properties using very high-frequency electromagnetic waves (light waves); Etude des proprietes des plasmas denses au moyen d'ondes electromagnetiques de tres haute frequence (ondes lumineuses)

    Energy Technology Data Exchange (ETDEWEB)

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

    1967-07-01

    A study is made of methods based on the use of lasers for measuring the electronic density and temperature of dense plasmas (N{sub e} > 10{sup 15}e/cm{sup 3}): - an interferometric method using a gas laser, based on the. properties of the Perot-Fabry cavities; - a method making use of the 90 deg C scattering produced by the plasma on light emitted by a ruby laser. These methods have been applied to various dense plasmas: - high-frequency plasma torch; - azimuth compression; - plasma bursts produced by focussing a laser beam on a metal target. The measurements have also been carried out using conventional methods of diagnosis. It has thus been possible to measure densities of between 5.10{sup 15} and 10{sup 19} e/cm{sup 3} and temperatures of between 3 and 10 eV. These different-methods are then compared, (author) [French] On etudie la mesure de la densite et de la temperature electronique des plasmas denses (N{sub e} > 10{sup 15} e/cm{sup 3}) a I'aide de methodes utilisant des lasers: - une methode interferometrique utilisant un laser a gaz, basee sur les proprietes des cavites Perot Fabry; -- une methode utilisant la diffusion a 900 deg C par le plasma de la lumiere issue d'un laser a rubis. Ces methodes ont ete appliquees sur differents plasmas denses: - Torche a plasma haute-frequence; - Compression azimutale; - Bouffees de plasma produites par la focalisation d'un faisceau laser sur une cible metallique. Les mesures ont ete egalement faites a I'aide de diagnostics classiques. On a pu ainsi mesurer des densites comprises entre 5.10{sup 15} et 10{sup 19} e/cm{sup 3} et des temperatures comprises entre 3 et 10 eV. On compare ensuite ces differentes methodes. (auteur)

  2. Study of dense-plasma properties using very high-frequency electromagnetic waves (light waves); Etude des proprietes des plasmas denses au moyen d'ondes electromagnetiques de tres haute frequence (ondes lumineuses)

    Energy Technology Data Exchange (ETDEWEB)

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

    1967-07-01

    A study is made of methods based on the use of lasers for measuring the electronic density and temperature of dense plasmas (N{sub e} > 10{sup 15}e/cm{sup 3}): - an interferometric method using a gas laser, based on the. properties of the Perot-Fabry cavities; - a method making use of the 90 deg C scattering produced by the plasma on light emitted by a ruby laser. These methods have been applied to various dense plasmas: - high-frequency plasma torch; - azimuth compression; - plasma bursts produced by focussing a laser beam on a metal target. The measurements have also been carried out using conventional methods of diagnosis. It has thus been possible to measure densities of between 5.10{sup 15} and 10{sup 19} e/cm{sup 3} and temperatures of between 3 and 10 eV. These different-methods are then compared, (author) [French] On etudie la mesure de la densite et de la temperature electronique des plasmas denses (N{sub e} > 10{sup 15} e/cm{sup 3}) a I'aide de methodes utilisant des lasers: - une methode interferometrique utilisant un laser a gaz, basee sur les proprietes des cavites Perot Fabry; -- une methode utilisant la diffusion a 900 deg C par le plasma de la lumiere issue d'un laser a rubis. Ces methodes ont ete appliquees sur differents plasmas denses: - Torche a plasma haute-frequence; - Compression azimutale; - Bouffees de plasma produites par la focalisation d'un faisceau laser sur une cible metallique. Les mesures ont ete egalement faites a I'aide de diagnostics classiques. On a pu ainsi mesurer des densites comprises entre 5.10{sup 15} et 10{sup 19} e/cm{sup 3} et des temperatures comprises entre 3 et 10 eV. On compare ensuite ces differentes methodes. (auteur)

  3. The strange physics of low frequency mirror mode turbulence in the high temperature plasma of the magnetosheath

    Directory of Open Access Journals (Sweden)

    R. A. Treumann

    2004-01-01

    Full Text Available Mirror mode turbulence is the lowest frequency perpendicular magnetic excitation in magnetized plasma proposed already about half a century ago by Rudakov and Sagdeev (1958 and Chandrasekhar et al. (1958 from fluid theory. Its experimental verification required a relatively long time. It was early recognized that mirror modes for being excited require a transverse pressure (or temperature anisotropy. In principle mirror modes are some version of slow mode waves. Fluid theory, however, does not give a correct physical picture of the mirror mode. The linear infinitesimally small amplitude physics is described correctly only by including the full kinetic theory and is modified by existing spatial gradients of the plasma parameters which attribute a small finite frequency to the mode. In addition, the mode is propagating only very slowly in plasma such that convective transport is the main cause of flow in it. As the lowest frequency mode it can be expected that mirror modes serve as one of the dominant energy inputs into plasma. This is however true only when the mode grows to large amplitude leaving the linear stage. At such low frequencies, on the other hand, quasilinear theory does not apply as a valid saturation mechanism. Probably the dominant processes are related to the generation of gradients in the plasma which serve as the cause of drift modes thus transferring energy to shorter wavelength propagating waves of higher nonzero frequency. This kind of theory has not yet been developed as it has not yet been understood why mirror modes in spite of their slow growth rate usually are of very large amplitudes indeed of the order of |B/B0|2~O(1. It is thus highly reasonable to assume that mirror modes are instrumental for the development of stationary turbulence in high temperature plasma. Moreover, since the magnetic field in mirror turbulence forms extended though slightly oblique magnetic bottles, low parallel energy particles can be trapped

  4. Spectroanalytical investigations on inductively coupled N2/Ar and Ar/Ar high frequency plasmas

    International Nuclear Information System (INIS)

    Malinowski, P.; Mazurkiewicz, M.; Nickel, H.

    1981-03-01

    In order to improve the detection limits of trace elements in corrosion products of metallic materials, the inductively coupled plasma excitation source (ICP) was applied for spectroscopic analysis. Besides optimizing the working conditions for the mentioned materials, the fundamental research clearing the excitation processes in ICP was carried out. Basicly, two plasma systems were investigated: the nitrogen cooled N 2 /Ar- and pure Ar/Ar-plasma. The computed detection limits for 8 chosen elements are between 0.1 and 50 μg ml -1 in both plasmas. The advantage of ion lines was clearly present; in N 2 /Ar-plasma it was larger than in Ar/Ar-plasma. The excitation temperatures measured with help of ArI, FeI and ZnI lines rise with increasing power and decreasing distance from the induction coil. The distribution of Zn excitation temperature in N 2 /Ar-plasma as well as the measured N + 2 rotational and CN vibrational temperatures indicate, that the toroidal structure of Ar/Ar-plasma is not analogue to the N 2 /Ar-plasma. The values of the various excitation temperatures (Ar, Fe, Zn) and the differences between the excitation, vibration, rotation and ionization temperatures (Tsub(i) > Tsub(n) = Tsub(vib) > Tsub(rot)) indicate an absence of thermal equilibrium in the concerned system. (orig.)

  5. Space-resolved characterization of high frequency atmospheric-pressure plasma in nitrogen, applying optical emission spectroscopy and numerical simulation

    International Nuclear Information System (INIS)

    Rajasekaran, Priyadarshini; Ruhrmann, Cornelia; Bibinov, Nikita; Awakowicz, Peter

    2011-01-01

    Averaged plasma parameters such as electron distribution function and electron density are determined by characterization of high frequency (2.4 GHz) nitrogen plasma using both experimental methods, namely optical emission spectroscopy (OES) and microphotography, and numerical simulation. Both direct and step-wise electron-impact excitation of nitrogen emissions are considered. The determination of space-resolved electron distribution function, electron density, rate constant for electron-impact dissociation of nitrogen molecule and the production of nitrogen atoms, applying the same methods, is discussed. Spatial distribution of intensities of neutral nitrogen molecule and nitrogen molecular ion from the microplasma is imaged by a CCD camera. The CCD images are calibrated using the corresponding emissions measured by absolutely calibrated OES, and are then subjected to inverse Abel transformation to determine space-resolved intensities and other parameters. The space-resolved parameters are compared, respectively, with the averaged parameters, and an agreement between them is established. (paper)

  6. Development of high power radio frequency components for fusion plasma heating. Final report, Revision 3

    International Nuclear Information System (INIS)

    1997-01-01

    The purpose of this CRADA was to develop advanced microwave heating systems for both ion cyclotron heating and electron cyclotron heating for magnetic fusion reactors. This involved low-frequency (UHF), high-power (millimeter-wave) microwave components, such as antennas, windows, and matching elements. This CRADA also involved developing conceptual designs for new microwave sources. General Atomics built and tested the distributed cooled window and provided LLNL with transmission and reflection test data in order to then benchmark the EM computer codes. The combline antenna built and analyzed by LLNL was based on a GA design. GA provided LLNL with a number of niobium plates for hot pressing and provided the necessary guidance to allow successful bonding. GA representatives were on site at LLNL on numerous occasions to consult and give guidance on the ferroelectric tuner, combline antenna and distributed window analysis

  7. Growth Processes of Particles up to Nanometer in High-Frequency SiH4 Plasmas

    International Nuclear Information System (INIS)

    Watanabe, Y.; Shiratani, M.; Fukuzawa, T.; Koga, K.

    2000-01-01

    Growth processes of particles in high-frequency SiH 4 discharges have been understood fairly well in a size range above 10 nm. Recently, we have developed two in situ particle detection methods to study those of particles (clusters) in a size range below ∼ 10 nm. The studies have clarified time evolution of their density and size and revealed the following facts: the cluster density amounts to ∼ 10 11 cm -3 under the device quality low-power and low-pressure conditions: the discharge modulation, substrate heating and H 2 dilution are quite effective in suppressing the cluster growth. We have proposed the cluster growth model explaining reasonably the obtained results. (author)

  8. Plasma rotation study in Tore Supra radio frequency heated plasmas

    International Nuclear Information System (INIS)

    Chouli, Bilal

    2014-01-01

    Toroidal flows are found to improve the performance of the magnetic confinement devices with increase of the plasma stability and confinement. In ITER or future reactors, the torque from NBI should be less important than in present-day tokamaks. Consequently, it is of interest to study other intrinsic mechanisms that can give rise to plasma rotation in order to predict the rotation profile in experiments. Intriguing observations of plasmas rotation have been made in radio frequency (RF) heated plasmas with little or no external momentum injection. Toroidal rotation in both the direction of the plasma current (co-current) and in the opposite direction (counter-current) has been observed depending on the heating schemes and plasma performance. In Tore Supra, most observations in L-mode plasmas have been in the counter-current direction. However, in this thesis, we show that in lower hybrid current drive (LHCD), the core toroidal rotation increment is in co- or counter-current direction depending on the plasma current amplitude. At low plasma current the rotation change is in the co-current direction while at high plasma current, the change is in the counter-current direction. In both low and high plasma current cases, rotation increments are found to increase linearly with the injected LH power. Several mechanisms in competition which can induce co- or counter-current rotation in Tore Supra LHCD plasmas are investigated and typical order of magnitude are discussed in this thesis. (author) [fr

  9. Frequency effects in silane plasmas for PECVD

    International Nuclear Information System (INIS)

    Howling, A.A.; Dorier, J.L.; Hollenstein, C.; Finger, F.; Kroll, U.

    1991-09-01

    It is generally recognised that the excitation frequency is an important parameter in rf plasma-assisted deposition. VHF silane plasmas (50-100 MHz) have been shown to produce high quality amorphous silicon films up to 20 A/s, and therefore the aim of this work is to compare the VHF range with the 13.56 MHz industrial frequency in the same reactor. The principal diagnostics used are electrical measurements and a CCD camera for spatially-resolved plasma-induced emission with Abel inversion of the plasma image. We present a comparative study of key discharge parameters such as deposition rates, plasma uniformity, ion impact energy, power transfer efficiency and powder formation for the rf range 13-70 MHz. (author) 5 figs., 19 refs

  10. An amplitude modulated radio frequency plasma generator

    Science.gov (United States)

    Lei, Fan; Li, Xiaoping; Liu, Yanming; Liu, Donglin; Yang, Min; Xie, Kai; Yao, Bo

    2017-04-01

    A glow discharge plasma generator and diagnostic system has been developed to study the effects of rapidly variable plasmas on electromagnetic wave propagation, mimicking the plasma sheath conditions encountered in space vehicle reentry. The plasma chamber is 400 mm in diameter and 240 mm in length, with a 300-mm-diameter unobstructed clear aperture. Electron densities produced are in the mid 1010 electrons/cm3. An 800 W radio frequency (RF) generator is capacitively coupled through an RF matcher to an internally cooled stainless steel electrode to form the plasma. The RF power is amplitude modulated by a waveform generator that operates at different frequencies. The resulting plasma contains electron density modulations caused by the varying power levels. A 10 GHz microwave horn antenna pair situated on opposite sides of the chamber serves as the source and detector of probe radiation. The microwave power feed to the source horn is split and one portion is sent directly to a high-speed recording oscilloscope. On mixing this with the signal from the pickup horn antenna, the plasma-induced phase shift between the two signals gives the path-integrated electron density with its complete time dependent variation. Care is taken to avoid microwave reflections and extensive shielding is in place to minimize electronic pickup. Data clearly show the low frequency modulation of the electron density as well as higher harmonics and plasma fluctuations.

  11. Plasma characteristics in an electrically asymmetric capacitive discharge sustained by multiple harmonics: operating in the very high frequency regime

    Science.gov (United States)

    Zhang, Yu-Ru; Hu, Yan-Ting; Gao, Fei; Song, Yuan-Hong; Wang, You-Nian

    2018-05-01

    A novel method, the so-called electrical asymmetry effect (EAE), is gaining increasing interest for realizing the separate control of the ion flux and ion energy. In this paper, a two-dimensional fluid model combined with the full set of Maxwell equations is used to investigate the plasma properties in an electrically asymmetric capacitive discharge sustained by multiple consecutive harmonics operating in the very high frequency regime. The results indicate that by increasing the total number of consecutive harmonics k, the modulation of the dc self-bias induced by changing {θ }1 (the relative phase of the fundamental frequency) becomes different, especially for k ≤slant 6. In a discharge driven by eight consecutive harmonics, the dc self-bias varies with a period 2π, and the most positive value appears at {θ }1 = 3π/2. In addition, with the electromagnetic effects taken into account, the plasma density shifts from edge-high to uniform when {θ }1 increases from 0 to π, and the maximum moves again towards the radial wall at {θ }1 = 3π/2. Moreover, the transient behavior of electrodynamics is also important for a better understanding of the EAE. Within a period, three positive peaks of {P}z are observed, which cause substantial ionization at similar places. {P}r is characterized by a pronounced peak at the end of the period, and the lowest peak value appears at {θ }1 = π. The results obtained in this work are important for improving the plasma processes by utilizing the EAE, especially when the higher order harmonics are included.

  12. Apparatus and method for enhanced chemical processing in high pressure and atmospheric plasmas produced by high frequency electromagnetic waves

    Science.gov (United States)

    Efthimion, Philip C.; Helfritch, Dennis J.

    1989-11-28

    An apparatus and method for creating high temperature plasmas for enhanced chemical processing of gaseous fluids, toxic chemicals, and the like, at a wide range of pressures, especially at atmospheric and high pressures includes an electro-magnetic resonator cavity, preferably a reentrant cavity, and a wave guiding structure which connects an electro-magnetic source to the cavity. The cavity includes an intake port and an exhaust port, each having apertures in the conductive walls of the cavity sufficient for the intake of the gaseous fluids and for the discharge of the processed gaseous fluids. The apertures are sufficiently small to prevent the leakage of the electro-magnetic radiation from the cavity. Gaseous fluid flowing from the direction of the electro-magnetic source through the guiding wave structure and into the cavity acts on the plasma to push it away from the guiding wave structure and the electro-magnetic source. The gaseous fluid flow confines the high temperature plasma inside the cavity and allows complete chemical processing of the gaseous fluids at a wide range of pressures.

  13. Si Nano wires Produced by Very High Frequency Plasma Enhanced Chemical Vapor Deposition (PECVD) via VLS Mechanism

    International Nuclear Information System (INIS)

    Yussof Wahab; Yussof Wahab; Habib Hamidinezhad; Habib Hamidinezhad

    2013-01-01

    Silicon nano wires (SiNWs) with diameter of about a few nanometers and length of 3 μm on silicon wafers were synthesized by very high frequency plasma enhanced chemical vapor deposition. Scanning electron microscopy (SEM) observations showed that the silicon nano wires were grown randomly and energy-dispersive X-ray spectroscopy analysis indicates that the nano wires have the composition of Si, Au and O elements. The SiNWs were characterized by high resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. SEM micrographs displayed SiNWs that are needle-like with a diameter ranged from 30 nm at the top to 100 nm at the bottom of the wire and have length a few of micrometers. In addition, HRTEM showed that SiNWs consist of crystalline silicon core and amorphous silica layer. (author)

  14. Zirconium dioxide ultrafine powders formation in ultra-high frequency discharge plasma

    International Nuclear Information System (INIS)

    Triotskij, V.N.; Kurkin, E.N.; Torbov, V.I.; Berestenko, V.I.; Torbova, O.D.; Gurov, S.V.; Alekseev, N.V.

    1995-01-01

    ZrO 2 fine powders of 30...60 nm particle size were synthesized by ZrCl 4 oxidation in a flow of oxygen microwave plasma. Oxygen flow rate and ZrCl 4 feeding rate were the defining parameters effecting on powder particles size at constant discharge power.At predominant contribution of the coalescence process into ZrO 2 powder particles formation their heterogeneous growth was shown necessary to take into account. 16 refs.; 5 figs

  15. Laser frequency modulation with electron plasma

    Science.gov (United States)

    Burgess, T. J.; Latorre, V. R.

    1972-01-01

    When laser beam passes through electron plasma its frequency shifts by amount proportional to plasma density. This density varies with modulating signal resulting in corresponding modulation of laser beam frequency. Necessary apparatus is relatively inexpensive since crystals are not required.

  16. Very high frequency plasma deposited amorphous/nanocrystalline silicon tandem solar cells on flexible substrates

    NARCIS (Netherlands)

    Liu, Y.|info:eu-repo/dai/nl/304831743

    2010-01-01

    The work in this thesis is to develop high quality intrinsic layers (especially nc-Si:H) for micromorph silicon tandem solar cells/modules on plastic substrates following the substrate transfer method or knows as the Helianthos procedure. Two objectives are covered in this thesis: (1) preliminary

  17. High energy plasma accelerators

    International Nuclear Information System (INIS)

    Tajima, T.

    1985-05-01

    Colinear intense laser beams ω 0 , kappa 0 and ω 1 , kappa 1 shone on a plasma with frequency separation equal to the electron plasma frequency ω/sub pe/ are capable of creating a coherent large longitudinal electric field E/sub L/ = mc ω/sub pe//e of the order of 1GeV/cm for a plasma density of 10 18 cm -3 through the laser beat excitation of plasma oscillations. Accompanying favorable and deleterious physical effects using this process for a high energy beat-wave accelerator are discussed: the longitudinal dephasing, pump depletion, the transverse laser diffraction, plasma turbulence effects, self-steepening, self-focusing, etc. The basic equation, the driven nonlinear Schroedinger equation, is derived to describe this system. Advanced accelerator concepts to overcome some of these problems are proposed, including the plasma fiber accelerator of various variations. An advanced laser architecture suitable for the beat-wave accelerator is suggested. Accelerator physics issues such as the luminosity are discussed. Applications of the present process to the current drive in a plasma and to the excitation of collective oscillations within nuclei are also discussed

  18. Multi-fluid Approach to High-frequency Waves in Plasmas. II. Small-amplitude Regime in Partially Ionized Media

    Energy Technology Data Exchange (ETDEWEB)

    Martínez-Gómez, David; Soler, Roberto; Terradas, Jaume, E-mail: david.martinez@uib.es [Departament de Física, Universitat de les Illes Balears, E-07122, Palma de Mallorca (Spain)

    2017-03-01

    The presence of neutral species in a plasma has been shown to greatly affect the properties of magnetohydrodynamic waves. For instance, the interaction between ions and neutrals through momentum transfer collisions causes the damping of Alfvén waves and alters their oscillation frequency and phase speed. When the collision frequencies are larger than the frequency of the waves, single-fluid magnetohydrodynamic approximations can accurately describe the effects of partial ionization, since there is a strong coupling between the various species. However, at higher frequencies, the single-fluid models are not applicable and more complex approaches are required. Here, we use a five-fluid model with three ionized and two neutral components, which takes into consideration Hall’s current and Ohm’s diffusion in addition to the friction due to collisions between different species. We apply our model to plasmas composed of hydrogen and helium, and allow the ionization degree to be arbitrary. By analyzing the corresponding dispersion relation and numerical simulations, we study the properties of small-amplitude perturbations. We discuss the effect of momentum transfer collisions on the ion-cyclotron resonances and compare the importance of magnetic resistivity, and ion–neutral and ion–ion collisions on the wave damping at various frequency ranges. Applications to partially ionized plasmas of the solar atmosphere are performed.

  19. Simulation of the influence high-frequency (2 MHz) capacitive gas discharge and magnetic field on the plasma sheath near a surface in hypersonic gas flow

    International Nuclear Information System (INIS)

    Schweigert, I. V.

    2012-01-01

    The plasma sheath near the surface of a hypersonic aircraft formed under associative ionization behind the shock front shields the transmission and reception of radio signals. Using two-dimensional kinetic particle-in-cell simulations, we consider the change in plasma-sheath parameters near a flat surface in a hypersonic flow under the action of electrical and magnetic fields. The combined action of a high-frequency 2-MHz capacitive discharge, a constant voltage, and a magnetic field on the plasma sheath allows the local electron density to be reduced manyfold.

  20. Exponential Frequency Spectrum in Magnetized Plasmas

    International Nuclear Information System (INIS)

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

    2008-01-01

    Measurements of a magnetized plasma with a controlled electron temperature gradient show the development of a broadband spectrum of density and temperature fluctuations having an exponential frequency dependence at frequencies below the ion cyclotron frequency. The origin of the exponential frequency behavior is traced to temporal pulses of Lorentzian shape. Similar exponential frequency spectra are also found in limiter-edge plasma turbulence associated with blob transport. This finding suggests a universal feature of magnetized plasma turbulence leading to nondiffusive, cross-field transport, namely, the presence of Lorentzian shaped pulses

  1. Plasma Immersion Ion Implantation in Radio Frequency Plasma

    International Nuclear Information System (INIS)

    Bora, B.; Bhuyan, H.; Wyndham, E.

    2013-01-01

    Plasma immersion ion implantation (PIII) has attracted wide interests since it emulates conventional ion-beam ion implantation (IBII) in niche applications. For instance, the technique has very high throughput, the implantation time is independent of the sample size, and samples with an irregular shape can be implanted without complex beam scanning or sample manipulation. For uniform ion implantation and deposition on to different substrates, like silicon, stainless steel etc., a capacitive coupled Radio frequency (RF), 13.6 MHz, plasma is used. During the PIII process, the physical parameters which are expected to play crucial rule in the deposition process like RF power, Negative pulse voltage and pulse duration, gas type and gas mixture, gas flow rates and the implantation dose are studied. The ion dose is calculated by dynamic sheath model and the plasma parameters are calculated from the V-I characteristic and power balance equation by homogeneous model of rf plasma discharge considering Ohmic as well as Stochastic heating. The correlations between the yield of the implantation process and the physical parameters as well as plasma parameters are discussed. (author)

  2. High efficiency high rate microcrystalline silicon thin-film solar cells deposited at plasma excitation frequencies larger than 100 MHz

    Czech Academy of Sciences Publication Activity Database

    Strobel, C.; Leszczynska, B.; Merkel, U.; Kuske, J.; Fischer, D.D.; Albert, M.; Holovský, Jakub; Michard, S.

    2015-01-01

    Roč. 143, Dec (2015), 347-353 ISSN 0927-0248 R&D Projects: GA MŠk 7E12029 EU Projects: European Commission(XE) 283501 - Fast Track Institutional support: RVO:68378271 Keywords : VHF * PECVD * microcrystalline silicon * solar cell * high rate * high efficiency Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.732, year: 2015

  3. MHD simulation of a beat frequency heated plasma

    International Nuclear Information System (INIS)

    Milroy, R.D.; Capjack, C.E.; James, C.R.; McMullin, J.N.

    1976-01-01

    The heating of a plasma in a solenoid, with a beat frequency harmonic which is excited at a frequency near to that of a Langmuir mode in a plasma, is examined. It is shown that at high temperatures the heating rate is very insensitive to changes in plasma density. The amount of energy that can be coupled to a plasma in a solenoid with this heating scheme is investigated by using a one-dimensional computer code which incorporates an exact solution of the relevant MHD equations. The absorption of energy from a high powered laser is shown to be significantly enhanced with this process. (author)

  4. Plasma Dispersion Functions for Complex Frequencies

    International Nuclear Information System (INIS)

    Pavlov, S. S.; Castejon, F.

    2005-01-01

    Plasma dispersion functions for complex wave propagation frequency in the weak relativistic regime for arbitrary longitudinal refractive index are estimated and presented in this work. These functions, that are know as Shkarofsky functions in the case of real frequency, are estimated using a new method that avoids the singularities that appear in previous calculations shown in the preceding literature. These results can be used to obtain the properties of plasma instabilities in the weakly relativistic regime. (Author) 14 refs

  5. Transparency of Magnetized Plasma at Cyclotron Frequency

    International Nuclear Information System (INIS)

    G. Shvets; J.S. Wurtele

    2002-03-01

    Electromagnetic radiation is strongly absorbed by a magnetized plasma if the radiation frequency equals the cyclotron frequency of plasma electrons. It is demonstrated that absorption can be completely canceled in the presence of a magnetostatic field of an undulator or a second radiation beam, resulting in plasma transparency at the cyclotron frequency. This effect is reminiscent of the electromagnetically induced transparency (EIT) of the three-level atomic systems, except that it occurs in a completely classical plasma. Unlike the atomic systems, where all the excited levels required for EIT exist in each atom, this classical EIT requires the excitation of the nonlocal plasma oscillation. The complexity of the plasma system results in an index of refraction at the cyclotron frequency that differs from unity. Lagrangian description was used to elucidate the physics and enable numerical simulation of the plasma transparency and control of group and phase velocity. This control naturally leads to applications for electromagnetic pulse compression in the plasma and electron/ion acceleration

  6. Ion heating, burnout of the high-frequency field, and ion sound generation under the development of a modulation instability of an intense Langmuir wave in a plasma

    Science.gov (United States)

    Kirichok, A. V.; Kuklin, V. M.; Pryimak, A. V.; Zagorodny, A. G.

    2015-09-01

    The development of one-dimensional parametric instabilities of intense long plasma waves is considered in terms of the so-called hybrid models, with electrons being treated as a fluid and ions being regarded as particles. The analysis is performed for both cases when the average plasma field energy is lower (Zakharov's hybrid model—ZHM) or greater (Silin's hybrid model—SHM) than the plasma thermal energy. The efficiency of energy transfer to ions and to ion perturbations under the development of the instability is considered for various values of electron-to-ion mass ratios. The energy of low-frequency oscillations (ion-sound waves) is found to be much lower than the final ion kinetic energy. We also discuss the influence of the changes in the damping rate of the high-frequency (HF) field on the instability development. The decrease of the absorption of the HF field inhibits the HF field burnout within plasma density cavities and gives rise to the broadening of the HF spectrum. At the same time, the ion velocity distribution tends to the normal distribution in both ZHM and SHM.

  7. Ion heating, burnout of the high-frequency field, and ion sound generation under the development of a modulation instability of an intense Langmuir wave in a plasma

    Energy Technology Data Exchange (ETDEWEB)

    Kirichok, A. V., E-mail: sandyrcs@gmail.com; Kuklin, V. M.; Pryimak, A. V. [Institute for High Technologies, V.N. Karazin Kharkiv National University, 4 Svobody Sq., Kharkiv 61022 (Ukraine); Zagorodny, A. G. [Bogolyubov Institute for Theoretical Physics, 14-b, Metrolohichna str., Kiev 03680 (Ukraine)

    2015-09-15

    The development of one-dimensional parametric instabilities of intense long plasma waves is considered in terms of the so-called hybrid models, with electrons being treated as a fluid and ions being regarded as particles. The analysis is performed for both cases when the average plasma field energy is lower (Zakharov's hybrid model—ZHM) or greater (Silin's hybrid model—SHM) than the plasma thermal energy. The efficiency of energy transfer to ions and to ion perturbations under the development of the instability is considered for various values of electron-to-ion mass ratios. The energy of low-frequency oscillations (ion-sound waves) is found to be much lower than the final ion kinetic energy. We also discuss the influence of the changes in the damping rate of the high-frequency (HF) field on the instability development. The decrease of the absorption of the HF field inhibits the HF field burnout within plasma density cavities and gives rise to the broadening of the HF spectrum. At the same time, the ion velocity distribution tends to the normal distribution in both ZHM and SHM.

  8. Highly selective etching of silicon nitride to physical-vapor-deposited a-C mask in dual-frequency capacitively coupled CH2F2/H2 plasmas

    International Nuclear Information System (INIS)

    Kim, J. S.; Kwon, B. S.; Heo, W.; Jung, C. R.; Park, J. S.; Shon, J. W.; Lee, N.-E.

    2010-01-01

    A multilevel resist (MLR) structure can be fabricated based on a very thin amorphous carbon (a-C) layer ( congruent with 80 nm) and Si 3 N 4 hard-mask layer ( congruent with 300 nm). The authors investigated the selective etching of the Si 3 N 4 layer using a physical-vapor-deposited (PVD) a-C mask in a dual-frequency superimposed capacitively coupled plasma etcher by varying the process parameters in the CH 2 F 2 /H 2 /Ar plasmas, viz., the etch gas flow ratio, high-frequency source power (P HF ), and low-frequency source power (P LF ). They found that under certain etch conditions they obtain infinitely high etch selectivities of the Si 3 N 4 layers to the PVD a-C on both the blanket and patterned wafers. The etch gas flow ratio played a critical role in determining the process window for infinitely high Si 3 N 4 /PVD a-C etch selectivity because of the change in the degree of polymerization. The etch results of a patterned ArF photoresisit/bottom antireflective coating/SiO x /PVD a-C/Si 3 N 4 MLR structure supported the idea of using a very thin PVD a-C layer as an etch-mask layer for the Si 3 N 4 hard-mask pattern with a pattern width of congruent with 80 nm and high aspect ratio of congruent with 5.

  9. Voltage tensor for a plasma in high frequency electromagnetic and constant electric fields in the presence of collisions

    International Nuclear Information System (INIS)

    Vigdorchik, N.E.

    1978-01-01

    The voltage tensor expression is obtained for plasma placed in a HF electromagnetic and constant electric fields. The kinetic equations with allowance for collisions are initial. Weakly ionized and completely ionized plasmas are considered. The voltage tensor for completely ionized plasma differs essentially from that for transparent media

  10. Plasma Temperature Determination of Hydrogen Containing High-Frequency Electrodeless Lamps by Intensity Distribution Measurements of Hydrogen Molecular Band

    OpenAIRE

    Gavare, Zanda; Revalde, Gita; Skudra, Atis

    2010-01-01

    The goal of the present work was the investigation of the possibility to use intensity distribution of the Q-branch lines of the hydrogen Fulcher-α diagonal band (d3Πu−→a3∑g+ electronic transition; Q-branch with v=v′=2) to determine the temperature of hydrogen containing high-frequency electrodeless lamps (HFEDLs). The values of the rotational temperatures have been obtained from the relative intensity distributions for hydrogen-helium and hydrogen-argon HFEDLs depending on the applied curren...

  11. ALMA High Frequency Techniques

    Science.gov (United States)

    Meyer, J. D.; Mason, B.; Impellizzeri, V.; Kameno, S.; Fomalont, E.; Chibueze, J.; Takahashi, S.; Remijan, A.; Wilson, C.; ALMA Science Team

    2015-12-01

    The purpose of the ALMA High Frequency Campaign is to improve the quality and efficiency of science observing in Bands 8, 9, and 10 (385-950 GHz), the highest frequencies available to the ALMA project. To this end, we outline observing modes which we have demonstrated to improve high frequency calibration for the 12m array and the ACA, and we present the calibration of the total power antennas at these frequencies. Band-to-band (B2B) transfer and bandwidth switching (BWSW), techniques which improve the speed and accuracy of calibration at the highest frequencies, are most necessary in Bands 8, 9, and 10 due to the rarity of strong calibrators. These techniques successfully enable increased signal-to-noise on the calibrator sources (and better calibration solutions) by measuring the calibrators at lower frequencies (B2B) or in wider bandwidths (BWSW) compared to the science target. We have also demonstrated the stability of the bandpass shape to better than 2.4% for 1 hour, hidden behind random noise, in Band 9. Finally, total power observing using the dual sideband receivers in Bands 9 and 10 requires the separation of the two sidebands; this procedure has been demonstrated in Band 9 and is undergoing further testing in Band 10.

  12. High frequency energy measurements

    International Nuclear Information System (INIS)

    Stotlar, S.C.

    1981-01-01

    High-frequency (> 100 MHz) energy measurements present special problems to the experimenter. Environment or available electronics often limit the applicability of a given detector type. The physical properties of many detectors are frequency dependent and in some cases, the physical effect employed can be frequency dependent. State-of-the-art measurements generally involve a detection scheme in association with high-speed electronics and a method of data recording. Events can be single or repetitive shot requiring real time, sampling, or digitizing data recording. Potential modification of the pulse by the detector and the associated electronics should not be overlooked. This presentation will review typical applications, methods of choosing a detector, and high-speed detectors. Special considerations and limitations of some applications and devices will be described

  13. Radio frequency induction plasma spraying of molybdenum

    International Nuclear Information System (INIS)

    Jiang Xianliang

    2003-01-01

    Radio frequency (RF) induction plasma was used to make free-standing deposition of molybdenum (Mo). The phenomena of particle melting, flattening, and stacking were investigated. The effect of process parameters such as plasma power, chamber pressure, and spray distance on the phenomena mentioned above was studied. Scanning electron microscopy (SEM) was used to analyze the plasma-processed powder, splats formed, and deposits obtained. Experimental results show that less Mo particles are spheroidized when compared to the number of spheroidized tungsten (W) particles at the same powder feed rate under the same plasma spray condition. Molten Mo particles can be sufficiently flattened on substrate. The influence of the process parameters on the flattening behavior is not significant. Mo deposit is not as dense as W deposit, due to the splash and low impact of molten Mo particles. Oxidation of the Mo powder with a large particle size is not evident under the low pressure plasma spray

  14. High frequency electromagnetic dosimetry

    CERN Document Server

    Sánchez-Hernández, David A

    2009-01-01

    Along with the growth of RF and microwave technology applications, there is a mounting concern about the possible adverse effects over human health from electromagnetic radiation. Addressing this issue and putting it into perspective, this groundbreaking resource provides critical details on the latest advances in high frequency electromagnetic dosimetry.

  15. Calculated experiment results on the study of possibility of power-effective high-frequency plasma heating

    International Nuclear Information System (INIS)

    Kokhanenko, I.K.; Zajtsev, A.A.

    1993-01-01

    A method for plasma anomalous heating by SHF radiation with variable power characteristics is considered. On the base of automodel system theory it is shown a possibility of providing for controlled plasma burning in a mode with 'sharpening'. Anomalous phenomena, appeared in experimental investigations of the SHF discharge, are explained

  16. A novel femtosecond-gated, high-resolution, frequency-shifted shearing interferometry technique for probing pre-plasma expansion in ultra-intense laser experiments

    Energy Technology Data Exchange (ETDEWEB)

    Feister, S., E-mail: feister.7@osu.edu; Orban, C. [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Innovative Scientific Solutions, Inc., Dayton, Ohio 45459 (United States); Nees, J. A. [Innovative Scientific Solutions, Inc., Dayton, Ohio 45459 (United States); Center for Ultra-Fast Optical Science, University of Michigan, Ann Arbor, Michigan 48109 (United States); Morrison, J. T. [Fellow, National Research Council, Washington, D.C. 20001 (United States); Frische, K. D. [Innovative Scientific Solutions, Inc., Dayton, Ohio 45459 (United States); Chowdhury, E. A. [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States); Intense Energy Solutions, LLC., Plain City, Ohio 43064 (United States); Roquemore, W. M. [Air Force Research Laboratory, Dayton, Ohio 45433 (United States)

    2014-11-15

    Ultra-intense laser-matter interaction experiments (>10{sup 18} W/cm{sup 2}) with dense targets are highly sensitive to the effect of laser “noise” (in the form of pre-pulses) preceding the main ultra-intense pulse. These system-dependent pre-pulses in the nanosecond and/or picosecond regimes are often intense enough to modify the target significantly by ionizing and forming a plasma layer in front of the target before the arrival of the main pulse. Time resolved interferometry offers a robust way to characterize the expanding plasma during this period. We have developed a novel pump-probe interferometry system for an ultra-intense laser experiment that uses two short-pulse amplifiers synchronized by one ultra-fast seed oscillator to achieve 40-fs time resolution over hundreds of nanoseconds, using a variable delay line and other techniques. The first of these amplifiers acts as the pump and delivers maximal energy to the interaction region. The second amplifier is frequency shifted and then frequency doubled to generate the femtosecond probe pulse. After passing through the laser-target interaction region, the probe pulse is split and recombined in a laterally sheared Michelson interferometer. Importantly, the frequency shift in the probe allows strong plasma self-emission at the second harmonic of the pump to be filtered out, allowing plasma expansion near the critical surface and elsewhere to be clearly visible in the interferograms. To aid in the reconstruction of phase dependent imagery from fringe shifts, three separate 120° phase-shifted (temporally sheared) interferograms are acquired for each probe delay. Three-phase reconstructions of the electron densities are then inferred by Abel inversion. This interferometric system delivers precise measurements of pre-plasma expansion that can identify the condition of the target at the moment that the ultra-intense pulse arrives. Such measurements are indispensable for correlating laser pre-pulse measurements

  17. Thermal Oxidation of a Carbon Condensate Formed in High-Frequency Carbon and Carbon-Nickel Plasma Flow

    Science.gov (United States)

    Churilov, G. N.; Nikolaev, N. S.; Cherepakhin, A. V.; Dudnik, A. I.; Tomashevich, E. V.; Trenikhin, M. V.; Bulina, N. G.

    2018-02-01

    We have reported on the comparative characteristics of thermal oxidation of a carbon condensate prepared by high-frequency arc evaporation of graphite rods and a rod with a hollow center filled with nickel powder. In the latter case, along with different forms of nanodisperse carbon, nickel particles with nickel core-carbon shell structures are formed. It has been found that the processes of the thermal oxidation of carbon condensates with and without nickel differ significantly. Nickel particles with the carbon shell exhibit catalytic properties with respect to the oxidation of nanosized carbon structures. A noticeable difference between the temperatures of the end of the oxidation process for various carbon nanoparticles and nickel particles with the carbon shell has been established. The study is aimed at investigations of the effect of nickel nanoparticles on the dynamics of carbon condensate oxidation upon heating in the argon-oxygen flow.

  18. Effect of low-frequency power on dual-frequency capacitively coupled plasmas

    International Nuclear Information System (INIS)

    Yuan, Q H; Xin, Y; Huang, X J; Sun, K; Ning, Z Y; Yin, G Q

    2008-01-01

    In low-pressure dual-frequency capacitively coupled plasmas driven with 60/13.56 MHz, the effect of low-frequency power on the plasma characteristics was investigated using a compensated Langmuir electrostatic probe. At lower pressures (about 10 mTorr), it was possible to control the plasma density and the ion bombardment energy independently. As the pressure increased, this independent control could not be achieved. As the low-frequency power increased for the fixed high-frequency power, the electron energy probability function (EEPF) changed from Druyvesteyn-like to Maxwellian-like at pressures of 50 mTorr and higher, along with a drop in electron temperature. The plasma parameters were calculated and compared with simulation results.

  19. Study and development of different techniques for the generation, conversion, propagation, and radiation of high power microwaves for the electronic cyclotron frequency plasma heating

    International Nuclear Information System (INIS)

    Rebuffi, L.

    1987-10-01

    The development and optimization of a microwave technique, concerning the high frequency (electronic cyclotron frequency) plasma heating is presented. The experiments are effectuated on the Fontenay-aux-Roses TFR tokamak, with 660 kw whole power, during 100 msec, produced at 60 GHz. Low power tests are performed on the different transmission line components (there are 3, formed by metallic circular waveguides). The work also includes: the development of a lens formed by thin metallic plans; the study of slotted surface mirror; the development of a system for the accurate measurement (5.10 -6 ) of the gyrotronic frequency; a theory, based on the equivalent circuits method, generalized to the rotational and polarization mirrors; the development of a numerical simulation code. A practical scheme, for the optimization of the parameters concerning the optical transmission line project, is given. The results of this work can be applied to the experiment involving power levels, frequencies and times of impulsion increasingly higher (respectively about MW, 100 GHz and 10s) than the reported ones. Moreover, they can also be used in any experiment in the microwave field [fr

  20. Plasma Temperature Determination of Hydrogen Containing High-Frequency Electrode less Lamps by Intensity Distribution Measurements of Hydrogen Molecular Band

    International Nuclear Information System (INIS)

    Gavare, Z.; Revalde, G.; Skudra, A.

    2011-01-01

    The goal of the present work was the investigation of the possibility to use intensity distribution of the Q-branch lines of the hydrogen Fulcher-a diagonal band (d3η u- a3Σg + electronic transition; Q-branch with ν=ν=2) to determine the temperature of hydrogen containing high-frequency electrode less lamps (HFEDLs). The values of the rotational temperatures have been obtained from the relative intensity distributions for hydrogen-helium and hydrogen-argon HFEDLs depending on the applied current. The results have been compared with the method of temperature derivation from Doppler profiles of He 667.8 nm and Ar 772.4 nm lines. The results of both methods are in good agreement, showing that the method of gas temperature determination from the intensity distribution in the hydrogen Fulcher-a (2-2)Q band can be used for the hydrogen containing HFEDLs. It was observed that the admixture of 10% hydrogen in the argon HFEDLs significantly reduces the gas temperature

  1. Simulation of a two-dimensional sheath over a flat insulator-conductor interface on a radio-frequency biased electrode in a high-density plasma

    International Nuclear Information System (INIS)

    Kim, Doosik; Economou, Demetre J.

    2004-01-01

    A combined fluid/Monte Carlo (MC) simulation was developed to study the two-dimensional (2D) sheath over a flat insulator/conductor interface on a radio-frequency (rf) biased electrode in a high-density plasma. The insulator capacitance increased the local impedance between the plasma and the bias voltage source. Thus, for uniform ion density and electron temperature far away from the wall, the sheath potential over the insulator was only a fraction of that over the conductor, resulting in a thinner sheath over the insulator. The fluid model provided the spatiotemporal profiles of the 2D sheath electric field. These were used as input to the MC simulation to compute the ion energy distribution (IED) and ion angular distribution (IAD) at different locations on the surface. The ion flux, IED, and IAD changed drastically across the insulator/conductor interface due to the diverging rf electric field in the distorted sheath. The ion flux was larger on the conductor at the expense of that on the insulator. Both the ion impact angle and angular spread increased progressively as the material interface was approached. The ion impact energy and energy spread were smaller on the insulator as compared to the conductor. For given plasma parameters, as the insulator thickness was increased, the sheath potential and thickness over the insulator decreased, and sheath distortion became more pronounced

  2. High-frequency modulation of ion-acoustic waves.

    Science.gov (United States)

    Albright, N. W.

    1972-01-01

    A large amplitude, high-frequency electromagnetic oscillation is impressed on a nonrelativistic, collisionless plasma from an external source. The frequency is chosen to be far from the plasma frequency (in fact, lower). The resulting electron velocity distribution function strongly modifies the propagation of ion-acoustic waves parallel to the oscillating electric field. The complex frequency is calculated numerically.

  3. Synthesis and analysis of silicon nanowire below Si-Au eutectic temperatures using very high frequency plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Hamidinezhad, Habib; Wahab, Yussof; Othaman, Zulkafli; Ismail, Abd Khamim

    2011-01-01

    Silicon nanowires (SiNWs) were synthesized from pure silane precursor gas and Au nanoparticles catalyst at below Au-Si eutectic temperature. The SiNWs were grown onto Si (1 1 1) substrates using very high frequency plasma enhanced chemical vapor deposition via a vapor-solid-solid mechanism at temperatures ranging from 363 to 230 deg. C. The morphology of the synthesized SiNWs was characterized by means of field emission scanning electron microscope equipped with energy dispersive X-ray, high resolution transmission electron microscopy, X-ray diffraction technique and Raman spectroscope. Results demonstrated that the SiNWs can be grown at the temperature as low as 250 deg. C. In addition, it was revealed that the grown wires were silicon-crystallized.

  4. High frequency asymptotic methods

    International Nuclear Information System (INIS)

    Bouche, D.; Dessarce, R.; Gay, J.; Vermersch, S.

    1991-01-01

    The asymptotic methods allow us to compute the interaction of high frequency electromagnetic waves with structures. After an outline of their foundations with emphasis on the geometrical theory of diffraction, it is shown how to use these methods to evaluate the radar cross section (RCS) of complex tri-dimensional objects of great size compared to the wave-length. The different stages in simulating phenomena which contribute to the RCS are reviewed: physical theory of diffraction, multiple interactions computed by shooting rays, research for creeping rays. (author). 7 refs., 6 figs., 3 insets

  5. HF heating of a plasma column at frequencies below the electron cyclotron frequency

    International Nuclear Information System (INIS)

    Datlov, J.; Kopecky, V.; Musil, J.; Zacek, F.; Novik, K.

    1978-02-01

    The dispersion of waves, excited by the helical structure in a plasma column and the heating of a tail of the electron distribution function is studied at frequencies below the electron plasma frequency and the electron cyclotron frequency. (author)

  6. Synthesis of High Crystalline Al-Doped ZnO Nanopowders from Al2O3 and ZnO by Radio-Frequency Thermal Plasma

    Directory of Open Access Journals (Sweden)

    Min-Kyeong Song

    2015-01-01

    Full Text Available High crystalline Al-doped ZnO (AZO nanopowders were prepared by in-flight treatment of ZnO and Al2O3 in Radio-Frequency (RF thermal plasma. Micron-sized (~1 μm ZnO and Al2O3 powders were mixed at Al/Zn ratios of 3.3 and 6.7 at.% and then injected into the RF thermal plasma torch along the centerline at a feeding rate of 6.6 g/min. The RF thermal plasma torch system was operated at the plate power level of ~140 kVA to evaporate the mixture oxides and the resultant vapor species were condensed into solid particles by the high flow rate of quenching gas (~7000 slpm. The FE-SEM images of the as-treated powders showed that the multipod shaped and the whisker type nanoparticles were mainly synthesized. In addition, these nanocrystalline structures were confirmed as the single phase AZO nanopowders with the hexagonal wurtzite ZnO structure by the XRD patterns and FE-TEM results with the SAED image. However, the composition changes of 0.3 and 1.0 at.% were checked for the as-synthesized AZO nanopowders at Al/Zn ratios of 3.3 and 6.7 at.%, respectively, by the XRF data, which can require the adjustment of Al/Zn in the mixture precursors for the applications of high Al doping concentrations.

  7. Improved planar radio frequency inductively coupled plasma configuration in plasma immersion ion implantation

    International Nuclear Information System (INIS)

    Tang, D.L.; Fu, R.K.Y.; Tian, X.B.; Chu, P.K.

    2003-01-01

    Plasmas with higher density and better uniformity are produced using an improved planar radio frequency (rf) inductively coupled plasma configuration in plasma immersion ion implantation (PIII). An axial magnetic field is produced by external electromagnetic coils outside the discharge chamber. The rf power can be effectively absorbed by the plasma in the vicinity of the electron gyrofrequency due to the enhanced resonant absorption of electromagnetic waves in the whistler wave range, which can propagate nearly along the magnetic field lines thus greatly increases the plasma density. The plasma is confined by a longitudinal multipolar cusp magnetic field made of permanent magnets outside the process chamber. It can improve the plasma uniformity without significantly affecting the ion density. The plasma density can be increased from 3x10 9 to 1x10 10 cm -3 employing an axial magnetic field of several Gauss at 1000 W rf power and 5x10 -4 Torr gas pressure. The nonuniformity of the plasma density is less than 10% and can be achieved in a process chamber with a diameter of 600 mm. Since the plasma generation and process chambers are separate, plasma extinction due to the plasma sheath touching the chamber wall in high-energy PIII can be avoided. Hence, low-pressure, high-energy, and high-uniformity ion implantation can be accomplished using this setup

  8. Excitation of a plasma by high frequencies for illumination purposes; Excitacion de un plasma por altas frecuencias para propositos de iluminacion

    Energy Technology Data Exchange (ETDEWEB)

    Valdivia B, R

    2003-07-01

    The power electronics plays a very important paper so much in the national as international industrial development. For that reason, many of the works are focused in the one analysis and amplification of this area with the purpose of finding improvements in the existent systems and always looking for oneself end: the energy saving. Moreover, in the last years has occurred great interest to other very important area given their properties of energy profit, novelty and mainly their wide range of applications. This area is the study and use of the plasma. Many institutions with international recognition already invest and they develop systems in these two big areas of the technology among those that is the National Institute of Nuclear Research (INlN) with some laboratories dedicated to the work of the plasma, one of them the Laboratory of Thermal Plasma Applications (LAPT). The conjugation of both areas was analysed and developed in the present work with the one purpose of designing a system to generate thermal plasma and to give him one or but applications like it is to produce a luminous source as like to degrade organic gases as the Methane or Acetylene. This was developed by means of a resonant inverter with the help of MOSFET IRFK2D450 transistors and a load L C in a serial-parallel configuration with the purpose to profit their condition of resonance to have the maximum transfer of energy to the plasma. For to have a best profit of the energy it was realized an analysis of design for to oblige to the transistors to commute in zero voltage (ZVS) and to avoid then lost of power of C A. (Author)

  9. Unexpected high plasma cobalamin

    DEFF Research Database (Denmark)

    Arendt, Johan F B; Nexo, Ebba

    2013-01-01

    It is well-established that more than 8% of patients examined for vitamin B12 deficiency unexpectedly have increased plasma levels of the vitamin, but so far there are no guidelines for the clinical interpretation of such findings. In this review, we summarise known associations between high plasma...... cobalamin binding proteins, transcobalamin and haptocorrin. Based on current knowledge, we suggest a strategy for the clinical interpretation of unexpected high plasma cobalamin. Since a number of the associated diseases are critical and life-threatening, the strategy promotes the concept of 'think...

  10. Plasma processing of superconducting radio frequency cavities

    Science.gov (United States)

    Upadhyay, Janardan

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

  11. High Frequency Oscillatory Ventilation

    Directory of Open Access Journals (Sweden)

    AC Bryan

    1996-01-01

    Full Text Available High frequency oscillatory (HFO ventilation using low tidal volume and peak airway pressures is extremely efficient at eliminating carbon dioxide and raising pH in the newborn infant with acute respiratory failure. Improvement in oxygenation requires a strategy of sustained or repetitive inflations to 25 to 30 cm H2O in order to place the lung on the deflation limb of the pressure-volume curve. This strategy has also been shown to decrease the amount of secondary lung injury in animal models. Experience of the use of HFO ventilation as a rescue therapy as well as several published controlled trials have shown improved outcomes and a decrease in the use of extracorporeal membrane oxygenation when it has been used in newborns.

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

    Science.gov (United States)

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

    2012-02-01

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

  13. Experimental Investigation on Frequency Characteristics of Plasma Synthetic Jets

    NARCIS (Netherlands)

    Zong, H.; Kotsonis, M.

    2017-01-01

    The performance of a two–electrode plasma synthetic jet actuator (PSJA) is investigated for a wide range of dimensionless actuation frequencies (f*) using high-speed phase-locked Particle Imaging Velocimetry (PIV) measurements. The jet-induced velocity fields in the

  14. Radio-frequency plasma spraying of ceramics

    International Nuclear Information System (INIS)

    Okada, T.; Hamatani, H.; Yoshida, T.

    1989-01-01

    This study was aimed at developing a novel spraying process using a radio-frequency (rf) plasma. Experiments of Al 2 O 3 and ZrO 2 - 8 wt% Y 2 O 3 spraying showed that the initial powder size was the most important parameter for depositing dense coatings. The optimum powder sizes of Al 2 O 3 and ZrO 2 - 8 wt% Y 2 O 3 were considered to be around 100 and 80 μm, respectively. The use of such large-size powders compared with those used by conventional dc plasma spraying made it possible to deposit adherent ceramics coatings of 150 to 300 μm on as-rolled SS304 substrates. It was also shown that low particle velocity of about 10 m/s, which is peculiar to rf plasma spraying, was sufficient for particle deformation, though it imposed a severe limitation on the substrate position. These experimental results prove that rf plasma spraying is an effective process and a strong candidate to open new fields of spraying applications

  15. High Frequency Design Considerations for the Large Detector Number and Small Form Factor Dual Electron Spectrometer of the Fast Plasma Investigation on NASA's Magnetospheric Multiscale Mission

    Science.gov (United States)

    Kujawski, Joseph T.; Gliese, Ulrik B.; Cao, N. T.; Zeuch, M. A.; White, D.; Chornay, D. J; Lobell, J. V.; Avanov, L. A.; Barrie, A. C.; Mariano, A. J.; hide

    2015-01-01

    Each half of the Dual Electron Spectrometer (DES) of the Fast Plasma Investigation (FPI) on NASA's Magnetospheric MultiScale (MMS) mission utilizes a microchannel plate Chevron stack feeding 16 separate detection channels each with a dedicated anode and amplifier/discriminator chip. The desire to detect events on a single channel with a temporal spacing of 100 ns and a fixed dead-time drove our decision to use an amplifier/discriminator with a very fast (GHz class) front end. Since the inherent frequency response of each pulse in the output of the DES microchannel plate system also has frequency components above a GHz, this produced a number of design constraints not normally expected in electronic systems operating at peak speeds of 10 MHz. Additional constraints are imposed by the geometry of the instrument requiring all 16 channels along with each anode and amplifier/discriminator to be packaged in a relatively small space. We developed an electrical model for board level interactions between the detector channels to allow us to design a board topology which gave us the best detection sensitivity and lowest channel to channel crosstalk. The amplifier/discriminator output was designed to prevent the outputs from one channel from producing triggers on the inputs of other channels. A number of Radio Frequency design techniques were then applied to prevent signals from other subsystems (e.g. the high voltage power supply, command and data handling board, and Ultraviolet stimulation for the MCP) from generating false events. These techniques enabled us to operate the board at its highest sensitivity when operated in isolation and at very high sensitivity when placed into the overall system.

  16. Influence of driving frequency on oxygen atom density in O2 radio frequency capacitively coupled plasma

    International Nuclear Information System (INIS)

    Kitajima, Takeshi; Noro, Kouichi; Nakano, Toshiki; Makabe, Toshiaki

    2004-01-01

    The influence of the driving frequency on the absolute oxygen atom density in an O 2 radio frequency (RF) capacitively coupled plasma (CCP) was investigated using vacuum ultraviolet absorption spectroscopy with pulse modulation of the main plasma. A low-power operation of a compact inductively coupled plasma light source was enabled to avoid the significant measurement errors caused by self-absorption in the light source. The pulse modulation of the main plasma enabled accurate absorption measurement for high plasma density conditions by eliminating background signals due to light emission from the main plasma. As for the effects of the driving frequency, the effect of VHF (100 MHz) drive on oxygen atom production was small because of the modest increase in plasma density of electronegative O 2 in contrast to the significant increase in electron density previously observed for electropositive Ar. The recombination coefficient of oxygen atoms on the electrode surface was obtained from a decay rate in the afterglow by comparison with a diffusion model, and it showed agreement with previously reported values for several electrode materials

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  18. DAMPING MECHANISM OF THE STRONGLY RENORMALIZED C-AXIS PLASMA FREQUENCY IN HIGH-T-C CUPRATES

    NARCIS (Netherlands)

    VANDERMAREL, D; KIM, JH; SOMAL, HS; FEENSTRA, BJ; WITTLIN, A; DUIJN, AVHM; MENOVSKY, A; LEE, WY

    1994-01-01

    We study the charge dynamics of high-T-c superconductors with the electric field perpendicular to the planes, using polarized oblique-incidence reflectometry for thin films of Tl2Ba2Ca2Cu(3)O(10) and normal incidence reflectometry for single crystals of La1.85Sr0.15CuO4. In Tl2Ba2Ca2Cu3O10 we

  19. High frequency breakdown voltage

    International Nuclear Information System (INIS)

    Chu, Thanh Duy.

    1992-03-01

    This report contains information about the effect of frequency on the breakdown voltage of an air gap at standard pressure and temperature, 76 mm Hg and O degrees C, respectively. The frequencies of interest are 47 MHz and 60 MHz. Additionally, the breakdown in vacuum is briefly considered. The breakdown mechanism is explained on the basis of collision and ionization. The presence of the positive ions produced by ionization enhances the field in the gap, and thus determines the breakdown. When a low-frequency voltage is applied across the gap, the breakdown mechanism is the same as that caused by the DC or static voltage. However, when the frequency exceeds the first critical value f c , the positive ions are trapped in the gap, increasing the field considerably. This makes the breakdown occur earlier; in other words, the breakdown voltage is lowered. As the frequency increases two decades or more, the second critical frequency, f ce , is reached. This time the electrons start being trapped in the gap. Those electrons that travel multiple times across the gap before reaching the positive electrode result in an enormous number of electrons and positive ions being present in the gap. The result is a further decrease of the breakdown voltage. However, increasing the frequency does not decrease the breakdown voltage correspondingly. In fact, the associated breakdown field intensity is almost constant (about 29 kV/cm).The reason is that the recombination rate increases and counterbalances the production rate, thus reducing the effect of the positive ions' concentration in the gap. The theory of collision and ionization does not apply to the breakdown in vacuum. It seems that the breakdown in vacuum is primarily determined by the irregularities on the surfaces of the electrodes. Therefore, the effect of frequency on the breakdown, if any, is of secondary importance

  20. Radio Frequency Plasma Applications for Space Propulsion

    International Nuclear Information System (INIS)

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

    1999-01-01

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

  1. Effects of cathode pulse at high frequency on structure and composition of Al2TiO5 ceramic coatings on Ti alloy by plasma electrolytic oxidation

    International Nuclear Information System (INIS)

    Yao Zhongping; Liu Yunfu; Xu Yongjun; Jiang Zhaohua; Wang Fuping

    2011-01-01

    Research highlights: → Al 2 TiO 5 in the coating on Ti alloy by PEO treatment changes with the increase of the cathode pulse, regardless of the amount and the grain size. → The cathode pulse brings about the decrease of γ-Al 2 O 3 and the increase of rutile TiO 2 in the coating. → The appropriate cathode pulse during PEO process is beneficial to reduce residual discharging channels and improve the density of the coating. - Abstract: The aim of this work is to investigate the effects of cathode pulse under high working frequency on structure and composition of ceramic coatings on Ti-6Al-4V alloys by plasma electrolytic oxidation (PEO). Ceramic coatings were prepared on Ti alloy by pulsed bi-polar plasma electrolytic oxidation in NaAlO 2 solution. The phase composition, morphology and element distribution in the coating were investigated by X-ray diffractometry, scanning electron microscopy and energy distribution spectroscopy, respectively. The coating was mainly composed of a large amount of Al 2 TiO 5 . As the cathode pulse was increased, the amount and grain size of Al 2 TiO 5 were first increased, and then decreased. γ-Al 2 O 3 in the coating was gradually decreased to nothing with the increase in the cathode pulse whereas rutile TiO 2 began to form in the coating. As opposed to the single-polar anode pulse mode, the cathode pulse reduced the thickness of the coatings. However, as the cathode pulse intensity continued to increase, the coating then became thicker regardless of cathode current density or pulse width. In addition, the residual discharging channels were reduced and the density of the coating was increased with the appropriate increase of the cathode pulse.

  2. Radio frequency emission from high-pressure xenon arcs: A systematic experimental analysis of the underlying near-anode plasma instability

    Energy Technology Data Exchange (ETDEWEB)

    Hechtfischer, Ulrich [Philips Lighting, GBU Automotive Lamps, Technology, Philipsstrasse 8, 52068 Aachen (Germany)

    2011-10-01

    High-pressure Xe discharge lamps at DC operation can show unwanted strong RF (radio-frequency) emission to beyond 1 GHz, correlated to a sharp periodic lamp-voltage instability in the near-anode plasma with a pulse repetition rate {epsilon} of 1-10 MHz. The physical origin of the instability is unclear. Here, its existence and pulse rate have been measured as a function of arc current I = 0.2-1.2 A and anode temperature T{sub a} = 1700-3400 K independently, in experimental lamps with pure-tungsten electrodes and a Xe operating pressure around p = 10 MPa. Surprisingly, the instability is not affected by I or current density j but exists if T{sub a} is lower than a threshold value around 2800-2900 K. The pulse rate {epsilon} is simply a rising linear function of the inverse anode temperature 1/T{sub a}, with only a small I-dependent correction. The average anode heat load is slightly lower in the unstable regime and possibly depends on {epsilon}. The results allow a consistent re-interpretation of earlier and present experimental observations and should be both a valuable help in practical lamp engineering and a tight constraint for future theories of this effect.

  3. Sources for high frequency heating. Performance and limitations

    International Nuclear Information System (INIS)

    Le Gardeur, R.

    1976-01-01

    The various problems encountered in high frequency heating of plasmas can be decomposed into three spheres of action: theoretical development, antenna designing, and utilization of power sources. By classifying heating into three spectral domains, present and future needs are enumerated. Several specific antenna designs are treated. High frequency power sources are reviewed. The actual development of the gyratron is discussed in view of future needs in very high frequency heating of plasmas [fr

  4. Study of a dual frequency atmospheric pressure corona plasma

    International Nuclear Information System (INIS)

    Kim, Dan Bee; Moon, S. Y.; Jung, H.; Gweon, B.; Choe, Wonho

    2010-01-01

    Radio frequency mixing of 2 and 13.56 MHz was investigated by performing experimental measurements on the atmospheric pressure corona plasma. As a result of the dual frequency, length, current density, and electron excitation temperature of the plasma were increased, while the gas temperature was maintained at roughly the same level when compared to the respective single frequency plasmas. Moreover, observation of time-resolved images revealed that the dual frequency plasma has a discharge mode of 2 MHz positive streamer, 2 MHz negative glow, and 13.56 MHz continuous glow.

  5. Generation of plasmas in water: utilization of a high-frequency, low-voltage bipolar pulse power supply with impedance control

    International Nuclear Information System (INIS)

    Baroch, P; Potocky, S; Saito, N

    2011-01-01

    Presented work focuses on the investigation and characterization of plasma discharges generated in water by newly developed bipolar pulse power supply. The main aim of our work was to solve and overcome problems with intensive arc discharge transition when the discharge is ignited and maintained by a low output impedance pulse power supply. For this purpose a novel type of bipolar pulse power supply was developed and tested. It was found that two distinguished stable modes of discharges generated in the water can be realized. Effects of water conductivity, pulse frequency and initial water temperature on the discharge properties were investigated. Optical emission spectroscopy was employed to study plasma parameters of the discharge and the correlation between the data obtained from the optical emission spectroscopy and the chemical species measured in the water was carried out.

  6. Binaural beats at high frequencies.

    Science.gov (United States)

    McFadden, D; Pasanen, E G

    1975-10-24

    Binaural beats have long been believed to be audible only at low frequencies, but an interaction reminiscent of a binaural beat can sometimes be heard when different two-tone complexes of high frequency are presented to the two ears. The primary requirement is that the frequency separation in the complex at one ear be slightly different from that in the other--that is, that there be a small interaural difference in the envelope periodicities. This finding is in accord with other recent demonstrations that the auditory system is not deaf to interaural time differences at high frequencies.

  7. Fundamental investigations of capacitive radio frequency plasmas: simulations and experiments

    International Nuclear Information System (INIS)

    Donkó, Z; Derzsi, A; Hartmann, P; Korolov, I; Schulze, J; Czarnetzki, U; Schüngel, E

    2012-01-01

    Capacitive radio frequency (RF) discharge plasmas have been serving hi-tech industry (e.g. chip and solar cell manufacturing, realization of biocompatible surfaces) for several years. Nonetheless, their complex modes of operation are not fully understood and represent topics of high interest. The understanding of these phenomena is aided by modern diagnostic techniques and computer simulations. From the industrial point of view the control of ion properties is of particular interest; possibilities of independent control of the ion flux and the ion energy have been utilized via excitation of the discharges with multiple frequencies. ‘Classical’ dual-frequency (DF) discharges (where two significantly different driving frequencies are used), as well as discharges driven by a base frequency and its higher harmonic(s) have been analyzed thoroughly. It has been recognized that the second solution results in an electrically induced asymmetry (electrical asymmetry effect), which provides the basis for the control of the mean ion energy. This paper reviews recent advances on studies of the different electron heating mechanisms, on the possibilities of the separate control of ion energy and ion flux in DF discharges, on the effects of secondary electrons, as well as on the non-linear behavior (self-generated resonant current oscillations) of capacitive RF plasmas. The work is based on a synergistic approach of theoretical modeling, experiments and kinetic simulations based on the particle-in-cell approach. (paper)

  8. 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.

  9. High frequency ignition arrangement

    Energy Technology Data Exchange (ETDEWEB)

    Canup, R E

    1977-03-03

    The invention concerns an HF ignition arrangement for combustion engines with a transistor oscillator. As this oscillator requires a current of 10A, with peak currents up to about 50A, it is not sensible to take this current through the remote ignition switch for switching it on and off. According to the invention the HF high voltage transformer of the ignition is provided with a control winding, which only requires a few milliamps DC and which can therefore be switched via the ignition switch. If the ignition switch is in the 'running' position, then a premagnetising DC current flows through the control winding, which suppresses the oscillation of the oscillator which has current flowing through it, until this current is interrupted by the interruptor contacts controlled by the combustion engine, so that the oscillations of the oscillator start immediately; the oscillator only continues to oscillate during the period during which the interruptor contacts controlled by the machine are open and interrupt the premagnetisation current. The control winding is short circuited in the 'off' position of the ignition switch.

  10. Spheroidization of molybdenum powder by radio frequency thermal plasma

    Science.gov (United States)

    Liu, Xiao-ping; Wang, Kuai-she; Hu, Ping; Chen, Qiang; Volinsky, Alex A.

    2015-11-01

    To control the morphology and particle size of dense spherical molybdenum powder prepared by radio frequency (RF) plasma from irregular molybdenum powder as a precursor, plasma process parameters were optimized in this paper. The effects of the carrier gas flow rate and molybdenum powder feeding rate on the shape and size of the final products were studied. The molybdenum powder morphology was examined using high-resolution scanning electron microscopy. The powder phases were analyzed by X-ray diffraction. The tap density and apparent density of the molybdenum powder were investigated using a Hall flow meter and a Scott volumeter. The optimal process parameters for the spherical molybdenum powder preparation are 50 g/min powder feeding rate and 0.6 m3/h carrier gas rate. In addition, pure spherical molybdenum powder can be obtained from irregular powder, and the tap density is enhanced after plasma processing. The average size is reduced from 72 to 62 µm, and the tap density is increased from 2.7 to 6.2 g/cm3. Therefore, RF plasma is a promising method for the preparation of high-density and high-purity spherical powders.

  11. Geographies of High Frequency Trading

    DEFF Research Database (Denmark)

    Grindsted, Thomas Skou

    2016-01-01

    This paper investigates the geographies of high frequency trading. Today shares shift hands within micro seconds, giving rise to a form of financial geographies termed algorithmic capitalism. This notion refers to the different spatio-temporalities produced by high frequency trading, under...... the valuation of time. As high frequency trading accelerates financial markets, the paper examines the spatio-temporalities of automated trading by the ways in which the speed of knowledge exploitation in financial markets is not only of interest, but also the expansion between different temporalities....... The paper demonstrates how the intensification of time-space compression produces radical new dynamics in the financial market and develops information rent in HFT as convertible to a time rent and a spatio-temporal rent. The final section discusses whether high frequency trading only responds to crises...

  12. Diamond deposition using a planar radio frequency inductively coupled plasma

    Science.gov (United States)

    Bozeman, S. P.; Tucker, D. A.; Stoner, B. R.; Glass, J. T.; Hooke, W. M.

    1995-06-01

    A planar radio frequency inductively coupled plasma has been used to deposit diamond onto scratched silicon. This plasma source has been developed recently for use in large area semiconductor processing and holds promise as a method for scale up of diamond growth reactors. Deposition occurs in an annulus which coincides with the area of most intense optical emission from the plasma. Well-faceted diamond particles are produced when the substrate is immersed in the plasma.

  13. Frequency effects and properties of plasma deposited fluorinated silicon nitride

    International Nuclear Information System (INIS)

    Chang, C.; Flamm, D.L.; Ibbotson, D.E.; Mucha, J.A.

    1988-01-01

    The properties of low-hydrogen, fluorinated plasma-enhanced chemical vapor deposition (PECVD) silicon nitride films grown using NF 3 /SiH 4 /N 2 feed mixtures in 200 kHz and 14 MHz discharges were compared. High-energy ion bombardment at 200 kHz is expected to enhance surface diffusion and chemical reconstruction. Compared to fluorinated silicon nitride deposited at 14 MHz under otherwise comparable conditions, the 200 kHz films had a lower Si--H bond concentration (approx. 21 cm -3 ), lower total hydrogen content (5--8 x 10 21 cm -3 ), better resistance to oxidation, lower compressive stress (-0.7 to -1.5 Gdyne/cm), and higher density (3.1 g/cm 3 ). The dielectric constant of better low-frequency Class I films was constant to 500 MHz, while that of high-frequency films fell up to 15% between 100 Hz and 10 MHz. The absorption edges of low-frequency PECVD fluorinated silicon nitride films were between 5.0 and 6.1 eV, which compare with 4.4 to 5.6 eV for the high-excitation frequency fluorinated material and 3 to 4 eV for conventional PECVD nitride. However high-frequency films may have fewer trap centers and a lower dielectric constant. 14 MHz p-SiN:F films grown with NH 3 as an auxiliary nitrogen source showed absorption edges similar to low-frequency material grown from NF 3 /SiH 4 /N 2 , but they have substantially more N--H bonding. The dielectric constant and absorption edge of these films were comparable to those of low-frequency p-SiN:F from NF 3 /SiH 4 /N 2

  14. Transparency of magnetized plasma at the cyclotron frequency

    International Nuclear Information System (INIS)

    Shvets, G.; Wurtele, J.S.

    2002-01-01

    Electromagnetic radiation is strongly absorbed by a magnetized plasma if the radiation frequency equals the cyclotron frequency of plasma electrons. It is demonstrated that absorption can be completely canceled in the presence of a magnetostatic field of an undulator, or a second radiation beam, resulting in plasma transparency at the cyclotron frequency. This effect is reminiscent of the electromagnetically induced transparency (EIT) of three-level atomic systems, except that it occurs in a completely classical plasma. Unlike the atomic systems, where all the excited levels required for EIT exist in each atom, this classical EIT requires the excitation of nonlocal plasma oscillation. A Lagrangian description was used to elucidate the physics of the plasma transparency and control of group and phase velocity. This control leads to applications for electromagnetic pulse compression and electron/ion acceleration

  15. The driving frequency effects on the atmospheric pressure corona jet plasmas from low frequency to radio frequency

    International Nuclear Information System (INIS)

    Kim, Dan Bee; Jung, H.; Gweon, B.; Rhee, J. K.; Choe, W.; Moon, S. Y.

    2011-01-01

    Lately, the atmospheric pressure jet type corona plasma, which has been typically driven by dc to low frequency (LF: several tens of kHz), is often generated by using radio frequency of 13.56 MHz. Yet, the relationship between the plasma and its driving frequency has seldom been investigated. Hence, in this study, dependence of the atmospheric pressure corona plasma characteristics on the driving frequency was explored experimentally from LF to rf (5 kHz-13.56 MHz). The plasmas generated by the driving frequency under 2 MHz were cylindrical shape of several tens of millimeters long while the 13.56 MHz plasma is spherical and a few millimeters long. As the driving frequency was increased, the plasma length became shortened. At the lower driving frequencies (below 2 MHz), the plasmas existed as positive streamer and negative glow for each half period of the applied voltage, but the discharge was more continuous in time for the 13.56 MHz plasma. It was inferred from the measured I-V curves that the higher driving frequency induced higher discharge currents, and the gas temperature was increased as the driving frequency was increased.

  16. High-temperature plasma physics

    International Nuclear Information System (INIS)

    Furth, H.P.

    1988-03-01

    Both magnetic and inertial confinement research are entering the plasma parameter range of fusion reactor interest. This paper reviews the individual and common technical problems of these two approaches to the generation of thermonuclear plasmas, and describes some related applications of high-temperature plasma physics

  17. Containment of high temperature plasmas

    International Nuclear Information System (INIS)

    Bass, R.W.; Ferguson, H.R.P.; Fletcher, H. Jr.; Gardner, J.; Harrison, B.K.; Larsen, K.M.

    1973-01-01

    Apparatus is described for confining a high temperature plasma which comprises: 1) envelope means shaped to form a toroidal hollow chamber containing a plasma, 2) magnetic field line generating means for confining the plasma in a smooth toroidal shape without cusps. (R.L.)

  18. 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.

  19. Some considerations about frequency tuning effects in ECRIS plasmas

    International Nuclear Information System (INIS)

    Mascali, D.; Gammino, S.; Celona, L.; Ciavola, G.; Neri, L.; Miracoli, R.; Gambino, N.; Castro, G.; Maimone, F.

    2012-01-01

    In the recent past many experiments demonstrated that slight variations of the microwave frequency used for the ignition of ECRIS plasmas strongly influence their performances (frequency tuning effect) either in terms of extracted current, of mean charge state and of beam emittance. According with theoretical investigations, this phenomenon can be explained by assuming that the plasma chamber works as a resonant cavity: the excited standing waves, whose spatial structure considerably changes with the pumping frequency, globally influences either the energy absorption rate and the plasma spatial structure. The paper is followed by the slides of the presentation. (authors)

  20. Very-low-frequency magnetic plasma

    International Nuclear Information System (INIS)

    Pendry, J.B.; O'Brien, S.

    2002-01-01

    We show that a set of current-carrying wires can exhibit an effective magnetic permeability at very low frequencies of a few hertz. The resonant permeability, which is negative above the resonance frequency, arises from the oscillations of the wires driven by the applied magnetic field. We show that a large, frequency-specific and tunable effective permeability can be realized for a wide range of strengths of the applied field. (author)

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  2. Charge density fluctuation of low frequency in a dusty plasma

    Institute of Scientific and Technical Information of China (English)

    李芳; 吕保维; O.Havnes

    1997-01-01

    The charge density fluctuation of low frequency in a dusty plasma, which is derived from the longitudinal dielectric permittivity of the dusty plasma, has been studied by kinetic theory. The results show that the P value, which describes the relative charge density on the dust in the plasma, and the charging frequency of a dust particle Ωc, which describes the ratio of charge changing of the dust particles, determine the character of the charge density fluctuation of low frequency. For a dusty plasma of P<<1, when the charging frequency Ωc is much smaller than the dusty plasma frequency wd, there is a strong charge density fluctuation which is of character of dust acoustic eigen wave. For a dusty plasma of P>>1, when the frequency Ωc, is much larger than wd there are weaker fluctuations with a wide spectrum. The results have been applied to the ionosphere and the range of radius and density of dust particles is found, where a strong charge density fluctuation of low frequency should exist.

  3. High-frequency Trader Subjectivity

    DEFF Research Database (Denmark)

    Borch, Christian; Lange, Ann-Christina

    2017-01-01

    In this article, we examine the recent shift in financial markets toward high-frequency trading (HFT). This turn is being legitimized with reference to how algorithms are allegedly more rational and efficient than human traders, and less prone to emotionally motivated decisions. We argue......-techniques of the ideal high-frequency trader. We demonstrate that these traders face the challenge of avoiding emotional interference in their algorithms and that they deploy a set of disciplinary self-techniques to curb the importance of emotional attachment....

  4. Low frequency phase signal measurement with high frequency squeezing

    OpenAIRE

    Zhai, Zehui; Gao, Jiangrui

    2011-01-01

    We calculate the utility of high-frequency squeezed-state enhanced two-frequency interferometry for low-frequency phase measurement. To use the high-frequency sidebands of the squeezed light, a two-frequency intense laser is used in the interferometry instead of a single-frequency laser as usual. We find that the readout signal can be contaminated by the high-frequency phase vibration, but this is easy to check and avoid. A proof-of-principle experiment is in the reach of modern quantum optic...

  5. Transparency of Magnetized Plasma at Cyclotron Frequency; TOPICAL

    International Nuclear Information System (INIS)

    G. Shvets; J.S. Wurtele

    2002-01-01

    Electromagnetic radiation is strongly absorbed by a magnetized plasma if the radiation frequency equals the cyclotron frequency of plasma electrons. It is demonstrated that absorption can be completely canceled in the presence of a magnetostatic field of an undulator or a second radiation beam, resulting in plasma transparency at the cyclotron frequency. This effect is reminiscent of the electromagnetically induced transparency (EIT) of the three-level atomic systems, except that it occurs in a completely classical plasma. Unlike the atomic systems, where all the excited levels required for EIT exist in each atom, this classical EIT requires the excitation of the nonlocal plasma oscillation. The complexity of the plasma system results in an index of refraction at the cyclotron frequency that differs from unity. Lagrangian description was used to elucidate the physics and enable numerical simulation of the plasma transparency and control of group and phase velocity. This control naturally leads to applications for electromagnetic pulse compression in the plasma and electron/ion acceleration

  6. LOMEGA: a low frequency, field implicit method for plasma simulation

    International Nuclear Information System (INIS)

    Barnes, D.C.; Kamimura, T.

    1982-04-01

    Field implicit methods for low frequency plasma simulation by the LOMEGA (Low OMEGA) codes are described. These implicit field methods may be combined with particle pushing algorithms using either Lorentz force or guiding center force models to study two-dimensional, magnetized, electrostatic plasmas. Numerical results for ωsub(e)deltat>>1 are described. (author)

  7. Global low-frequency modes in weakly ionized magnetized plasmas: effects of equilibrium plasma rotation

    International Nuclear Information System (INIS)

    Sosenko, P.; Pierre, Th.; Zagorodny, A.

    2004-01-01

    The linear and non-linear properties of global low-frequency oscillations in cylindrical weakly ionized magnetized plasmas are investigated analytically for the conditions of equilibrium plasma rotation. The theoretical results are compared with the experimental observations of rotating plasmas in laboratory devices, such as Mistral and Mirabelle in France, and KIWI in Germany. (authors)

  8. Development of frequency tunable gyrotrons for plasma diagnostics

    International Nuclear Information System (INIS)

    Idehara, T.; Mitsudo, S.; Sabchevski, S.; Glyavin, M.; Ogawa, I.; Sato, M.; Kawahata, K.; Brand, G.F.

    2000-01-01

    Development of two types of frequency tunable gyrotrons are described. One is frequency step-tunable gyrotrons (Gyrotron FU Series) which cover wide range from millimeter to submillimeter wavelength region. The other is a quasi-optical gyrotron operating in 90 and 180 GHz bands. Both are applicable for plasma diagnostics as power sources. (author)

  9. Electro-optical frequency shifting of lasers for plasma diagnostics

    International Nuclear Information System (INIS)

    Forman, P.R.

    1977-07-01

    An electro-optical frequency shifting device is proposed as an aid for plasma physics heterodyne interferometry and heterodyne scattering experiments. The method has the advantage over other electro-optic shifters, that a pure separable frequency shifted beam can be obtained even when less than half wave voltage is applied. (orig.) [de

  10. Controlling plasma properties under differing degrees of electronegativity using odd harmonic dual frequency excitation

    Science.gov (United States)

    Gibson, Andrew R.; Gans, Timo

    2017-11-01

    The charged particle dynamics in low-pressure oxygen plasmas excited by odd harmonic dual frequency waveforms (low frequency of 13.56 MHz and high frequency of 40.68 MHz) are investigated using a one-dimensional numerical simulation in regimes of both low and high electronegativity. In the low electronegativity regime, the time and space averaged electron and negative ion densities are approximately equal and plasma sustainment is dominated by ionisation at the sheath expansion for all combinations of low and high frequency and the phase shift between them. In the high electronegativity regime, the negative ion density is a factor of 15-20 greater than the low electronegativity cases. In these cases, plasma sustainment is dominated by ionisation inside the bulk plasma and at the collapsing sheath edge when the contribution of the high frequency to the overall voltage waveform is low. As the high frequency component contribution to the waveform increases, sheath expansion ionisation begins to dominate. It is found that the control of the average voltage drop across the plasma sheath and the average ion flux to the powered electrode are similar in both regimes of electronegativity, despite the differing electron dynamics using the considered dual frequency approach. This offers potential for similar control of ion dynamics under a range of process conditions, independent of the electronegativity. This is in contrast to ion control offered by electrically asymmetric waveforms where the relationship between the ion flux and ion bombardment energy is dependent upon the electronegativity.

  11. Nonlinear nonresonant forces by radio-frequency waves in plasmas

    International Nuclear Information System (INIS)

    Gao Zhe; Fisch, Nathaniel J.; Qin, Hong; Myra, J. R.

    2007-01-01

    Nonresonant forces by applied rf waves in plasmas are analyzed. Along the background dc magnetic field, the force arises from the gradient of the ponderomotive potential. Only when the dc magnetic field is straight, however, is this parallel force completely consistent with that from the single particle picture, where the ponderomotive force depends on the gradients of rf fields only. Across the dc magnetic field, besides the ponderomotive force from the particle picture, additional Reynolds stress and polarization stress contribute to the total force. For waves with frequency much lower than the cyclotron frequency, the perpendicular forces from the particle and fluid pictures can have opposite signs. In plasmas with a symmetry angle (e.g., toroidal systems), nonresonant forces cannot drive net flow or current in the flux surface, but the radial force may influence macroscopic behavior of plasma. Moreover, nonresonant forces may drive flow or current in linear plasmas or in a localized region of toroidal plasmas

  12. Plasma heating by radio frequency in the LISA linear machine

    International Nuclear Information System (INIS)

    Cunha Raposo, C. da.

    1985-05-01

    The characteristics of an experimental apparatus to produce helium plasma by radio frequency and to study its behavior when confined by a magnetic field with mirrors is shown. The plasma was produced by a microwave source of 2.45 GHz and 800 Watts, operating in steady and pulsed state. The plasma parameters were studied as a function of an external magnetic field, for large and small resonance regions. The axial and radial magnetic fields were mapped for each region in order to verify the spatial distribution, particle orbits, and energy confinement time according to the energy balance equation. As a consequence of the influence of the radio frequency (RF) voltage in the plasma the Bohm theory of plasma prob was modified. The diagnostic was done with plane movable electrostatic probe, Hall probe, magnetic probe, diamagnetic coil and spectrography. (Author) [pt

  13. Plasma acceleration in a wave with varying frequency

    International Nuclear Information System (INIS)

    Petrzilka, V.A.

    1978-01-01

    The averaged velocity of a test particle and the averaged velocity of a plasma in an electromagnetic wave packet with varying frequency (e.g., a radiation pulse from pulsar) is derived. The total momentum left by the wave packet in regions of plasma inhomogeneity is found. In case the plasma concentration is changing due to ionization the plasma may be accelerated parallelly or antiparallelly to the direction of the wave packet propagation which is relevant for a laser induced breakdown in gas. (author)

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

    Science.gov (United States)

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

    1973-01-01

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

  15. Frequency upshift via flash ionization phenomena using semiconductor plasma

    Directory of Open Access Journals (Sweden)

    Nishida A.

    2013-11-01

    Full Text Available We have demonstrated frequency upshift in the terahertz region by flash ionization. The magnitude of upshift frequency is tuned by the laser intensity. A proof of principle experiment has been performed with a plasma creation time scale much shorter than the period of the electromagnetic wave and a plasma length longer than its wavelength. Frequency upshifted from 0.35 to 3.5 THz by irradiating a ZnSe crystal with a ultra-short laser pulse has been observed.

  16. High-frequency, high-intensity photoionization

    Science.gov (United States)

    Reiss, H. R.

    1996-02-01

    Two analytical methods for computing ionization by high-frequency fields are compared. Predicted ionization rates compare well, but energy predictions for the onset of ionization differ radically. The difference is shown to arise from the use of a transformation in one of the methods that alters the zero from which energy is measured. This alteration leads to an apparent energy threshold for ionization that can, especially in the stabilization regime, differ strongly from the laboratory measurement. It is concluded that channel closings in intense-field ionization can occur at high as well as low frequencies. It is also found that the stabilization phenomenon at high frequencies, very prominent for hydrogen, is absent in a short-range potential.

  17. High-Frequency Seafloor Acoustics

    CERN Document Server

    Jackson, Darrell R

    2007-01-01

    High-Frequency Seafloor Acoustics is the first book in a new series sponsored by the Office of Naval Research on the latest research in underwater acoustics. This exciting new title provides ready access to experimental data, theory, and models relevant to high-frequency seafloor acoustics and will be of interest to sonar engineers and researchers working in underwater acoustics. The physical characteristics of the seafloor affecting acoustic propagation and scattering are covered, including physical and geoacoustic properties and surface roughness. Current theories for acoustic propagation in sediments are presented along with corresponding models for reflection, scattering, and seafloor penetration. The main text is backed up by an extensive bibliography and technical appendices.

  18. 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)

  19. Epitaxial growth of GaN by radical-enhanced metalorganic chemical vapor deposition (REMOCVD) in the downflow of a very high frequency (VHF) N2/H2 excited plasma - effect of TMG flow rate and VHF power

    Science.gov (United States)

    Lu, Yi; Kondo, Hiroki; Ishikawa, Kenji; Oda, Osamu; Takeda, Keigo; Sekine, Makoto; Amano, Hiroshi; Hori, Masaru

    2014-04-01

    Gallium nitride (GaN) films have been grown by using our newly developed Radical-Enhanced Metalorganic Chemical Vapor Deposition (REMOCVD) system. This system has three features: (1) application of very high frequency (60 MHz) power in order to increase the plasma density, (2) introduction of H2 gas together with N2 gas in the plasma discharge region to generate not only nitrogen radicals but also active NHx molecules, and (3) radical supply under remote plasma arrangement with suppression of charged ions and photons by employing a Faraday cage. Using this new system, we have studied the effect of the trimethylgallium (TMG) source flow rate and of the plasma generation power on the GaN crystal quality by using scanning electron microscopy (SEM) and double crystal X-ray diffraction (XRD). We found that this REMOCVD allowed the growth of epitaxial GaN films of the wurtzite structure of (0001) orientation on sapphire substrates with a high growth rate of 0.42 μm/h at a low temperature of 800 °C. The present REMOCVD is a promising method for GaN growth at relatively low temperature and without using costly ammonia gas.

  20. Improved GAMMA 10 tandem mirror confinement in high density plasma

    International Nuclear Information System (INIS)

    Yatsu, K.; Cho, T.; Higaki, H.; Hirata, M.; Hojo, H.; Ichimura, M.; Ishii, K.; Ishimoto, Y.; Itakura, A.; Katanuma, I.; Kohagura, J.; Minami, R.; Nakashima, Y.; Numakura, T.; Saito, T.; Saosaki, S.; Takemura, Y.; Tatematsu, Y.; Yoshida, M.; Yoshikawa, M.

    2003-01-01

    GAMMA 10 experiments have advanced in high density experiments after the last IAEA fusion energy conference in 2000 where we reported the production of the high density plasma through use of ion cyclotron range of frequency heating at a high harmonic frequency and neutral beam injection in the anchor cells. However, the diamagnetic signal of the plasma decreased when electron cyclotron resonance heating was applied for the potential formation. Recently a high density plasma has been obtained without degradation of the diamagnetic signal and with much improved reproducibility than before. The high density plasma was attained through adjustment of the spacing of the conducting plates installed in the anchor transition regions. The potential confinement of the plasma has been extensively studied. Dependences of the ion confinement time, ion-energy confinement time and plasma confining potential on plasma density were obtained for the first time in the high density region up to a density of 4x10 18 m -3 . (author)

  1. Design and development of ITER high-frequency magnetic sensor

    NARCIS (Netherlands)

    Ma, Y.; Vayakis, G.; Begrambekov, L. B.; Cooper, J.J.; Duran, I.; Hirsch, M.; Laqua, H.P.; Moreau, Ph.; Oosterbeek, J.W.; Spuig, P.; Stange, T.; Walsh, M.

    2016-01-01

    High-frequency (HF) inductive magnetic sensors are the primary ITER diagnostic set for Toroidal Alfvén Eigenmodes (TAE) detection, while they also supplement low-frequency MHD and plasma equilibrium measurements. These sensors will be installed on the inner surface of ITER vacuum vessel, operated in

  2. Manipulating Electromagnetic Waves in Magnetized Plasmas: Compression, Frequency Shifting, and Release

    International Nuclear Information System (INIS)

    Avitzour, Yoav; Shvets, Gennady

    2008-01-01

    A new approach to manipulating the duration and frequency of microwave pulses using magnetized plasmas is demonstrated. The plasma accomplishes two functions: (i) slowing down and spatially compressing the incident wave, and (ii) modifying the propagation properties (group velocity and frequency) of the wave in the plasma during a uniform in space adiabatic in time variation of the magnitude and/or direction of the magnetic field. The increase in the group velocity results in the shortening of the temporal pulse duration. Depending on the plasma parameters, the frequency of the outgoing compressed pulse can either change or remain unchanged. Such dynamic manipulation of radiation in plasma opens new avenues for manipulating high power microwave pulses

  3. The JET high frequency pellet injector project

    International Nuclear Information System (INIS)

    Geraud, Alain; Dentan, M.; Whitehead, A.; Butcher, P.; Communal, D.; Faisse, F.; Gedney, J.; Gros, G.; Guillaume, D.; Hackett, L.; Hennion, V.; Homfray, D.; Lucock, R.; McKivitt, J.; Sibbald, M.; Portafaix, C.; Perin, J.P.; Reade, M.; Sands, D.; Saille, A.

    2007-01-01

    A new deuterium ice pellet injector is in preparation for JET. It is designed to inject both small pellets (variable volume within 1-2 mm 3 ) at high frequency (up to 60 Hz) for ELM mitigation experiments and large pellets (volume within 35-70 mm 3 ) at moderate frequency (up to 15 Hz) for plasma fuelling. It is based on the screw extruder technology developed by PELIN and pneumatic acceleration. An injection line will connect the injector to the flight tubes already in place to convey the pellets toward the plasma either from the low field side or from the high field side of the torus. This injection line enables: (i) the pumping of the propellant gas, (ii) the provision of the vacuum interface with the torus and (iii) the selection of the flight tube to be used via a fast selector. All the interfaces have been designed and a prototype injector is being built, to demonstrate that the required performance is achievable

  4. Atomic Oxygen Energy in Low Frequency Hyperthermal Plasma Ashers

    Science.gov (United States)

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

    2014-01-01

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

  5. High-frequency magnetic components

    CERN Document Server

    Kazimierczuk, Marian K

    2013-01-01

    A unique text on the theory and design fundaments of inductors and transformers, updated with more coverage on the optimization of magnetic devices and many new design examples The first edition is popular among a very broad audience of readers in different areas of engineering and science. This book covers the theory and design techniques of the major types of high-frequency power inductors and transformers for a variety of applications, including switching-mode power supplies (SMPS) and resonant dc-to-ac power inverters and dc-to-dc power converters. It describes eddy-current phenomena (su

  6. Low-frequency waves in magnetized dusty plasmas revisited

    International Nuclear Information System (INIS)

    Salimullah, M.; Khan, M.I.; Amin, R.; Nitta, H.; Shukla, P.K.

    2005-10-01

    The general dispersion relation of any wave is examined for low-frequency waves in a homogeneous dusty plasma in the presence of an external magnetic field. The low-frequency parallel electromagnetic wave propagates as a dust cyclotron wave or a whistler in the frequency range below the ion cyclotron frequency. In the same frequency regime, the transverse electromagnetic magnetosonic wave is modified with a cutoff frequency at the dust-ion lower-hybrid frequency, which reduces to the usual magnetosonic wave in absence of the dust. Electrostatic dust-lower- hybrid mode is also recovered propagating nearly perpendicular to the magnetic field with finite ion temperature and cold dust particles which for strong ion-Larmor radius effect reduces to the usual dust-acoustic wave driven by the ion pressure. (author)

  7. Radio frequency conductivity of plasma in inhomogeneous magnetic field

    International Nuclear Information System (INIS)

    Itoh, Sanae; Nishikawa, Kyoji; Fukuyama, Atsushi; Itoh, Kimitaka.

    1985-01-01

    Nonlocal conductivity tensor is obtained to study the kinetic effects on propagation and absorption of radio frequency (rf) waves in dispersive plasmas. Generalized linear propagator in the presence of the inhomogeneity of magnetic field strength along the field line is calculated. The influence of the inhomogeneity to the rf wave-energy deposition is found to be appreciable. Application to toroidal plasmas is shown. (author)

  8. Overview of Spontaneous Frequency Chirping in Confined Plasmas

    Science.gov (United States)

    Berk, Herbert

    2012-10-01

    Spontaneous rapid frequency chirping is now a commonly observed phenomenon in plasmas with an energetic particle component. These particles typically induce so called weak instabilities, where they excite background waves that the plasma can support such as shear Alfven waves. The explanation for this phenomenon attributes the frequency chirping to the formation of phase space structures in the form of holes and clumps. Normally a saturated mode, in the presence of background dissipation, would be expected decay after saturation as the background plasma absorbs the energy of the excited wave. However the phase space structures take an alternate route, and move to a regions of phase space that are lower energy states of the energetic particle distribution. Through the wave-resonant particle interaction, this movement is locked to the frequency observed by the wave. This phenomenon implies that alternate mechanisms for plasma relaxation need to be considered for plasma states new marginal stability. It is also possible that these chirping mechanisms can be used to advantage to externally control states of plasma.

  9. Experimental test of models of radio-frequency plasma sheaths

    International Nuclear Information System (INIS)

    Sobolewski, M.A.

    1997-01-01

    The ion current and sheath impedance were measured at the radio-frequency-powered electrode of an asymmetric, capacitively coupled plasma reactor, for discharges in argon at 1.33 endash 133 Pa. The measurements were used to test the models of the radio frequency sheath derived by Lieberman [IEEE Trans. Plasma Sci. 17, 338 (1989)] and Godyak and Sternberg [Phys. Rev. A 42, 2299 (1990)], and establish the range of pressure and sheath voltage in which they are valid. copyright 1997 American Institute of Physics

  10. Synthesis of cobalt boride nanoparticles using radio frequency thermal plasma

    International Nuclear Information System (INIS)

    Lapitan, Jr. Lorico DS.; Ying Ying Chen; Seesoek Choe; Watanabe, Takayuki

    2012-01-01

    Nano size cobalt boride particles were synthesized from vapor phase using a 30 kw-4 MHz radio frequency (RF) thermal plasma. Cobalt and boron powder mixtures used as precursors in different composition and feed rate were evaporated immediately in the high temperature plasma and cobalt boride nanoparticles were produced through the quenching process. The x-ray diffractometry (XRD) patterns of cobalt boride nanoparticles prepared from the feed powder ratio of 1:2 and 1:3 for Co: B showed peaks that are associated with the Co 2 B and CoB crystal phases of cobalt boride. The XRD analysis revealed that increasing the powder feed rate results in a higher mass fraction and a larger crystalline diameter of cobalt boride nanoparticles. The images obtained by field emission scanning electron microscopy (FE-SEM) revealed that cobalt boride nanoparticles have a spherical morphology. The crystallite size of the particles estimated with XRD was found to be 18-22 nm. (author)

  11. Frequency mixing in boron carbide laser ablation plasmas

    Science.gov (United States)

    Oujja, M.; Benítez-Cañete, A.; Sanz, M.; Lopez-Quintas, I.; Martín, M.; de Nalda, R.; Castillejo, M.

    2015-05-01

    Nonlinear frequency mixing induced by a bichromatic field (1064 nm + 532 nm obtained from a Q-switched Nd:YAG laser) in a boron carbide (B4C) plasma generated through laser ablation under vacuum is explored. A UV beam at the frequency of the fourth harmonic of the fundamental frequency (266 nm) was generated. The dependence of the efficiency of the process as function of the intensities of the driving lasers differs from the expected behavior for four-wave mixing, and point toward a six-wave mixing process. The frequency mixing process was strongly favored for parallel polarizations of the two driving beams. Through spatiotemporal mapping, the conditions for maximum efficiency were found for a significant delay from the ablation event (200 ns), when the medium is expected to be a low-ionized plasma. No late components of the harmonic signal were detected, indicating a largely atomized medium.

  12. High Temperature Radio Frequency Loads

    CERN Document Server

    Federmann, S; Grudiev, A; Montesinos, E; Syratchev, I

    2011-01-01

    In the context of energy saving and recovery requirements the design of reliable and robust RF power loads which permit a high outlet temperature and high pressure of the cooling water is desirable. Cooling water arriving at the outlet withmore than 150 ◦C and high pressure has a higher value than water with 50 ◦C under low pressure. Conventional RF power loads containing dielectric and magnetic materials as well as sensitive ceramic windows usually do not permit going much higher than 90 ◦C. Here we present and discuss several design concepts for "metal only" RF high power loads. One concept is the application of magnetic steel corrugated waveguides near cutoff – this concept could find practical use above several GHz. Another solution are resonant structures made of steel to be installed in large waveguides for frequencies of 500 MHz or lower. Similar resonant structures above 100 MHz taking advantage of the rather high losses of normal steel may also be used in coaxial line geometries with large di...

  13. CONFINEMENT OF HIGH TEMPERATURE PLASMA

    Science.gov (United States)

    Koenig, H.R.

    1963-05-01

    The confinement of a high temperature plasma in a stellarator in which the magnetic confinement has tended to shift the plasma from the center of the curved, U-shaped end loops is described. Magnetic means are provided for counteracting this tendency of the plasma to be shifted away from the center of the end loops, and in one embodiment this magnetic means is a longitudinally extending magnetic field such as is provided by two sets of parallel conductors bent to follow the U-shaped curvature of the end loops and energized oppositely on the inside and outside of this curvature. (AEC)

  14. Influence of the low-frequency source parameters on the plasma characteristics in a dual frequency capacitively coupled plasma reactor: Two dimensional simulations

    Institute of Scientific and Technical Information of China (English)

    Xiang Xu; Hao Ge; Shuai Wang; Zhongling Dai; Younian Wang; Aimin Zhu

    2009-01-01

    A two-dimensional (2D) fluid model is presented to study the discharge of argon in a dual frequency capacitively coupled plasma (CCP) reactor. We are interested in the influence of low-frequency (LF) source parameters such as applied voltage amplitudes and low frequencies on the plasma characteristics. In this paper, the high frequency is set to 60 MHz with voltage 50 V. The simulations were carried out for low frequencies of 1, 2 and 6 MHz with LF voltage 100 V, and for LF voltages of 60, 90 and 120 V with low frequency 2 MHz. The results of 2D distributions of electric field and ion density, the ion flux impinging on the substrate and the ion energy on the powered electrode are shown. As the low frequency increases, two sources become from uncoupling to coupling, When two sources are uncoupling, the increase in LF has little impact on the plasma characteristics, but when two sources are coupling, the increase in LF decreases the uniformities of ion density and ion flux noticeably. It is also found that with the increase in LF voltage, the uniformities in the radial direction of ion density distribution and ion flux at the powered electrode decreases significantly, and the energy of ions bombarding on the powered electrode increases significantly.

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

    Science.gov (United States)

    Puac, N.

    2008-07-01

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

  16. Plasma particle drifts due to traveling waves with cyclotron frequencies

    International Nuclear Information System (INIS)

    Hatakeyama, Rikizo; Sato, Naoyuki; Sato, Noriyoshi

    1991-01-01

    A particle orbit theory yields that traveling waves with cyclotron frequencies give rise to charged particle drifts perpendicular both to the wave propagation and external magnetic field lines. The result is applicable to particle-flux control of magnetized plasmas. (author)

  17. Plasma Equilibrium in a Torus with High-Frequency Fields and Plasma Heating Resulting from the Development of a Powerful Beam of ''Escaping Electrons''; Plasma Torique: Stabilisation au Moyen de Champs de Haute Frequence et Chauffage par Formation d'un Flux Intense d'Electrons 'Emballes'; Ehksperimental'noe issledovanie ravnovesiya plazmy v tore pri nalichii vysokochastotnykh polej i nagreva plazmy za schet razvitiya moshchnogo puchka ''ubegayushchikh ehlektronov''; Equilibrio del Plasma en un Toro, en Presencia de Campos de Alta Frecuencia, y Calentamiento del Plasma por el Desarrollo de un Haz Potente de 'Electrones Desbocados '

    Energy Technology Data Exchange (ETDEWEB)

    Demirkhanov, R. A.; Kirov, A. G.; Stotland, M. A.; Malykh, N. I.; Horasanov, G. L.; Vishnevskij, N. K.; Gutkin, T. I.; Jampol' skij, I. R. [Fiziko-Tehnicheskij Institut Gosudarstvennogo Komiteta po Ispol' zovaniju Atomnoj Ehnergii SSSR, Sukhumi, SSSR (Russian Federation)

    1966-04-15

    The paper describes experiments conducted on the ''RT-0'' apparatus. It consists of a torus with large diameter 100 cm and with small diameter 10 cm. A toroidal magnetic field about 6 kOe is established along the chamber. The plasma is ignited at {>=}5 x 10{sup -4} Torr by means of a longitudinal rotating electric field of f = 8.3 Mc/s. Rotating around the small diameter is a high-frequency (540 kc/s) quadrupole field with H{phi} = 200 Oe at the chamber walls. When the low-induction capacitor bank is discharged on the loops located along the torus, a damped vortical electric field with maximum strength E{sub z} = 200 V cm{sup -1} and with half-period about 1 {mu}s may be generated within the chamber. The purposes of the experiments were: 1) To explain the equilibrium and stabilization of plasma in a quasi-constant toroidal magnetic field by using routing multipole high-frequency fields, on the assumption that the toroidal drift force, equal to Tilde-Operator (r/R)nkt, must be compensated by the electromagnetic wave pressure H{sup 2}/8{pi}; 2) To study the heating of plasma resulting from dissipation of the ''beam'' instability produced by a powerful beam of ''escaping electrons'' when the electric fields in the plasma are characterized by Ez >> Ec. The apparatus was used to carry out: a) Microwave measurements of plasma density, by using an interferometer of wave length {lambda} =2 mm, and observation of the plasma boundary by the reflected signal on the wave {lambda} = 17 mm; b) Recording of the behaviour of the H{sub {beta}} line in time and scanning of plasma luminescence in time, by using a photoelectric converter; c) measurement of the total intensity of the X-radiation in time, by using a scintillation counter; d) measurement of the current in the plasma and of the voltage in the bypass. The results show that a high-frequency igniting field of 8.3 Mc/s creates a plasma touching the walls with an average electron density 0.5 to 1 x 10{sup 13} cm{sup -3} and an

  18. ITER Plasma at Ion Cyclotron Frequency Domain: The Fusion Alpha Particles Diagnostics Based on the Stimulated Raman Scattering of Fast Magnetosonic Wave off High Harmonic Ion Bernstein Modes

    Science.gov (United States)

    Stefan, V. Alexander

    2014-10-01

    A novel method for alpha particle diagnostics is proposed. The theory of stimulated Raman scattering, SRS, of the fast wave and ion Bernstein mode, IBM, turbulence in multi-ion species plasmas, (Stefan University Press, La Jolla, CA, 2008). is utilized for the diagnostics of fast ions, (4)He (+2), in ITER plasmas. Nonlinear Landau damping of the IBM on fast ions near the plasma edge leads to the space-time changes in the turbulence level, (inverse alpha particle channeling). The space-time monitoring of the IBM turbulence via the SRS techniques may prove efficient for the real time study of the fast ion velocity distribution function, spatial distribution, and transport. Supported by Nikola Tesla Labs., La Jolla, CA 92037.

  19. Extraordinary mode absorption at the electron cyclotron harmonic frequencies as a Tokamak plasma diagnostic

    International Nuclear Information System (INIS)

    Pachtman, A.

    1986-09-01

    Measurements of Extraordinary mode absorption at the electron cyclotron harmonic frequencies are of unique value in high temperature, high density Tokamak plasma diagnostic applications. An experimental study of Extraordinary mode absorption at the semi-opaque second and third harmonics has been performed on the ALCATOR C Tokamak. A narrow beam of submillimeter laser radiation was used to illuminate the plasma in a horizontal plane, providing a continuous measurement of the one-pass, quasi-perpendicular transmission

  20. Exponential frequency spectrum and Lorentzian pulses in magnetized plasmas

    International Nuclear Information System (INIS)

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

    2008-01-01

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

  1. Low-frequency REB modulation and acceleration of ions in a supercritical mode during plasma injection

    International Nuclear Information System (INIS)

    Chupikov, P.T.; Medvedev, D.V.; Onishchenko, I.N.; Panasenko, B.D.

    2004-01-01

    Low-frequency modulation of a high-current relativistic electron beam (REB) and acceleration of ions in the first section of a collective ion accelerator as studied experimentally. This modulation was obtained due to periodic compensation of a virtual cathode charge by plasma ions. An ion flow was produced by an electric field of virtual cathode when plasma assists. Plasma was formed by the four Bostick plasma guns placed at equal distance along the periphery of the drift chamber. The low-frequency modulation with depth 10 % at frequency 46 MHz was obtained. The ion energy was measured using the magnetic analyzer. The ion energy that probably was obtained in the potential well of the virtual cathode exceeded the REB energy

  2. Preparation of hydrogenated amorphous carbon films using a microsecond-pulsed DC capacitive-coupled plasma chemical vapor deposition system operated at high frequency up to 400 kHz

    Science.gov (United States)

    Mamun, Md Abdullah Al; Furuta, Hiroshi; Hatta, Akimitsu

    2018-06-01

    Hydrogenated amorphous carbon (a-C:H) films are deposited on silicon (Si) substrates using a high-repetition microsecond-pulsed DC plasma chemical vapor deposition (CVD) system from acetylene (C2H2) at a gas pressure of 15 Pa inside a custom-made vacuum chamber. The plasma discharge characteristics, hydrocarbon species, and the microstructure of the resulting films are examined at various pulse repetition rates from 50 to 400 kHz and a fixed duty cycle of 50%. The optical emission spectra confirmed the increase in electron excitation energy from 1.09 to 1.82 eV and the decrease in the intensity ratio of CH/C2 from 1.04 to 0.75 with increasing pulse frequency, indicating the enhanced electron impact dissociation of C2H2 gas. With increasing pulse frequency, the deposition rate gradually increased, reaching a maximum rate of 60 nm/min at 200 kHz, after which a progressive decrease was noted, whereas the deposition area was almost uniform for all the prepared films. Clear trends of increasing sp3 content (amorphization) and decreasing hydrogen (H) content in the films were observed as the pulse repetition rate increased, while most of the hydrogen atoms bonded to carbon atoms by sp3 hybridization rather than by sp2 hybridization.

  3. Sum frequency generation for studying plasma-wall interactions

    International Nuclear Information System (INIS)

    Roke, Sylvie

    2010-01-01

    Interaction of a plasma with a surface results in chemical and physical restructuring of the surface as well as the plasma in the vicinity of the surface. Studying such a reorganization of the atoms and molecules in the surface layer requires optical tools that can penetrate the plasma environment. At the same time, surface specificity is required. Sum Frequency Generation (SFG) is an optical method that fulfills these requirements. SFG has been developed into a surface specific probe during the eighties and nineties. Nowadays SFG is routinely applied in the research of complex interfaces. In such experiments, liquid/gas, solid/gas, solid/liquid, or liquid/liquid interfaces are probed, and the chemical surface composition, orientational distribution, order and chirality can be retrieved. An application to investigate plasma-wall interactions is feasible too.

  4. High Throughput Plasma Water Treatment

    Science.gov (United States)

    Mujovic, Selman; Foster, John

    2016-10-01

    The troublesome emergence of new classes of micro-pollutants, such as pharmaceuticals and endocrine disruptors, poses challenges for conventional water treatment systems. In an effort to address these contaminants and to support water reuse in drought stricken regions, new technologies must be introduced. The interaction of water with plasma rapidly mineralizes organics by inducing advanced oxidation in addition to other chemical, physical and radiative processes. The primary barrier to the implementation of plasma-based water treatment is process volume scale up. In this work, we investigate a potentially scalable, high throughput plasma water reactor that utilizes a packed bed dielectric barrier-like geometry to maximize the plasma-water interface. Here, the water serves as the dielectric medium. High-speed imaging and emission spectroscopy are used to characterize the reactor discharges. Changes in methylene blue concentration and basic water parameters are mapped as a function of plasma treatment time. Experimental results are compared to electrostatic and plasma chemistry computations, which will provide insight into the reactor's operation so that efficiency can be assessed. Supported by NSF (CBET 1336375).

  5. High current plasma electron emitter

    International Nuclear Information System (INIS)

    Fiksel, G.; Almagri, A.F.; Craig, D.

    1995-07-01

    A high current plasma electron emitter based on a miniature plasma source has been developed. The emitting plasma is created by a pulsed high current gas discharge. The electron emission current is 1 kA at 300 V at the pulse duration of 10 ms. The prototype injector described in this paper will be used for a 20 kA electrostatic current injection experiment in the Madison Symmetric Torus (MST) reversed-field pinch. The source will be replicated in order to attain this total current requirement. The source has a simple design and has proven very reliable in operation. A high emission current, small size (3.7 cm in diameter), and low impurity generation make the source suitable for a variety of fusion and technological applications

  6. High temperature divertor plasma operation

    International Nuclear Information System (INIS)

    Ohyabu, Nobuyoshi.

    1991-02-01

    High temperature divertor plasma operation has been proposed, which is expected to enhance the core energy confinement and eliminates the heat removal problem. In this approach, the heat flux is guided through divertor channel to a remote area with a large target surface, resulting in low heat load on the target plate. This allows pumping of the particles escaping from the core and hence maintaining of the high divertor temperature, which is comparable to the core temperature. The energy confinement is then determined by the diffusion coefficient of the core plasma, which has been observed to be much lower than the thermal diffusivity. (author)

  7. Radio Frequency Power in Plasmas: 12th Topical Conference. Proceedings

    International Nuclear Information System (INIS)

    Ryan, P.M.; Intrator, T.

    1997-01-01

    The twelfth Topical Conference on Radio Frequency Power in Plasmas was held in April, 1997, in Georgia, USA under the sponsorship of Oak Ridge National Laboratory of the US Department of Energy, the University of Wisconsin, and the American Physical Society. A large part of the conference was devoted to the ion cyclotron range of frequencies. Radio frequency contributions to the creation and maintenance of transport barriers to both particle and heat flux received a lot of attention. In addition to plasma heating, the use of RF as a versatile tool to drive current, shape profiles and stabilize plasmas was also discussed. The RF systems designs for ITER, ICRF heating advances on helical devices were among the topics of interest, so were progress in ion cyclotron codes, advanced launchers and technology, RF startup, general wave theory and the application of RF plasmas to material processing. A total of 103 papers were presented and are included in these proceedings. Out of these, 54 have been abstracted for the Energy Science and Technology database

  8. Investigation of Capacitively Coupled Argon Plasma Driven by Dual-Frequency with Different Frequency Configurations

    International Nuclear Information System (INIS)

    Yu Yiqing; Xin Yu; Ning Zhaoyuan; Lu Wenqi

    2011-01-01

    Low pressure argon dual-frequency (DF) capacitively coupled plasma (CCP) is generated by using different frequency configurations, such as 13.56/2, 27/2, 41/2, and 60/2 MHz. Characteristics of the plasma are investigated by using a floating double electrical probe and optical emission spectroscopy (OES). It is shown that in the DF-CCPs, the electron temperature T e decreases with the increase in exciting frequency, while the onset of 2 MHz induces a sudden increase in T e and the electron density increases basically with the increase in low frequency (LF) power. The intensity of 750.4 nm emission line increases with the LF power in the case of 13.56/2 MHz, while different tendencies of line intensity with the LF power appear for other configurations. The reason for this is also discussed.

  9. Investigation of Combined High-Frequency and Arc Discharges

    International Nuclear Information System (INIS)

    Taran, V.S.; Nezovibatko, Yu.N.; Marinin, V.G.; Shvets, O.M.; Ridozub, V.N.; Gasilin, V.V.

    2001-01-01

    In this paper we analyze experiment with arc and high-frequency (HF) plasma sources carried out in modified devise of the ''Bulat'' type. The HF-sources and combined discharges have attracted considerable attention for surface cleaning and coating. The utilization of such discharges allows decreasing droplet fraction formation and providing better adhesion and microhardness values. The existence of HF-field in plasma allows obtaining either conductive or dielectric coatings and they can be deposited on any substrates. (author)

  10. Frequency threshold for ion beam formation in expanding RF plasma

    Science.gov (United States)

    Chakraborty Thakur, Saikat; Harvey, Zane; Biloiu, Ioana; Hansen, Alex; Hardin, Robert; Przybysz, William; Scime, Earl

    2008-11-01

    We observe a threshold frequency for ion beam formation in expanding, low pressure, argon helicon plasma. Mutually consistent measurements of ion beam energy and density relative to the background ion density obtained with a retarding field energy analyzer and laser induced fluorescence indicate that a stable ion beam of 15 eV appears for source frequencies above 11.5 MHz. Reducing the frequency increases the upstream beam amplitude. Downstream of the expansion region, a clear ion beam is seen only for the higher frequencies. At lower frequencies, large electrostatic instabilities appear and an ion beam is not observed. The upstream plasma density increases sharply at the same threshold frequency that leads to the appearance of a stable double layer. The observations are consistent with the theoretical prediction that downstream electrons accelerated into the source by the double layer lead to increased ionization, thus balancing the higher loss rates upstream [1]. 1. M. A. Lieberman, C. Charles and R. W. Boswell, J. Phys. D: Appl. Phys. 39 (2006) 3294-3304

  11. Econometrics of financial high-frequency data

    CERN Document Server

    Hautsch, Nikolaus

    2011-01-01

    This book covers major approaches in high-frequency econometrics. It discusses implementation details, provides insights into properties of high-frequency data as well as institutional settings and presents applications.

  12. Parametrically induced low-frequency waves in weakly inhomogeneous magnetized plasmas

    International Nuclear Information System (INIS)

    Pesic, S.

    1981-01-01

    The linear dispersion relation governing the parametric interaction of a lower hybrid pump wave with a weakly-inhomogeneous current carrying hot plasma confined by a helical magnetic field is derived and solved numerically. The stability boundaries are delineated over a wide range in the k-space. The frequency and growth rate of decay instabilities are calculated for plasma parameters relevant to lower hybrid plasma heating experiments. The parametric excitation of drift waves and ion cyclotron current instabilities is discussed. In the low-density plasma region low minimum thresholds and high growth rates are obtained for the pump decay into ion cyclotron and nonresonant quasimodes. The spatial amplification of hot ion Bernstein waves and nonresonant quasimodes dominate in the plasma core (ω 0 /ωsub(LH) < 2). The presented theoretical results are in qualitative agreement with current LH plasma heating experiments. (author)

  13. Two-temperature model of the energy balance for the plasma of a high-frequency induction discharge near the plasmoid axis

    International Nuclear Information System (INIS)

    Gerasimov, A.V.; Kirpichnikov, A.P.

    2000-01-01

    On the basis of analysis of the equation system for energy balance within near-the-axis range of HF-plasmatron inductor in terms of a two-temperature model one derived the analytical dependences to calculate temperature fields within that range in a two-dimensional definition of the problem. Paper presents the results of calculations carried out for various cross sections of HF-discharge plasmoid. The calculations were carried out for the air plasma under the atmospheric pressure. The derived formulae describe rather accurately distribution of temperature fields near the plasmoid axis and may be applied to tackle rather wide scope of problems dealing with heat transfer [ru

  14. Numerical Simulation of Spheroidization Process of TiAl Alloy Powders in Radio Frequency Plasma

    OpenAIRE

    ZHU Langping; LU Xin; LIU Chengcheng; LI Jianchong; NAN Hai

    2017-01-01

    A numerical simulation method was used to study the radio frequency plasma spheroidization process of TiAl alloy powder. The effects of velocity field and temperature field on the motion trajectory and mass change of TiAl alloy powder with different particle size were analyzed.The results show that the temperature of powder particles increases rapidly under high temperature plasma, surface evaporation cause the reduction of particle size, and particles with small size tend to evaporate quickl...

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

    International Nuclear Information System (INIS)

    Ruzic, David N.

    2013-01-01

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

  16. Frequency Upconversion and Parametric Surface Instabilities in Microwave Plasma Interactions.

    Science.gov (United States)

    Rappaport, Harold Lee

    In this thesis the interaction of radiation with plasmas whose density profiles are nearly step functions of space and/or time are studied. The wavelengths of radiation discussed are large compared with plasma density gradient scale lengths. The frequency spectra are evaluated and the energy balance investigated for the transmitted and reflected transient electromagnetic waves that are generated when a monochromatic source drives a finite width plasma in which a temporal step increase in density occurs. Transmission resonances associated with the abrupt boundaries manifest themselves as previously unreported multiple frequency peaks in the transmitted electromagnetic spectrum. A tunneling effect is described in which a burst of energy is transmitted from the plasma immediately following a temporal density transition. Stability of an abruptly bounded plasma, one for which the incident radiation wavelength is large compared with the plasma density gradient scale length, is investigated for both s and p polarized radiation types. For s-polarized radiation a new formalism is introduced in which pump induced perturbations are expressed as an explicit superposition of linear and non-linear plasma half-space modes. Results for a particular regime and a summary of relevant literature is presented. We conclude that when s-polarized radiation acts alone on an abrupt diffusely bounded underdense plasma stimulated excitation of electron surface modes is suppressed. For p-polarized radiation the recently proposed Lagrangian Frame Two-Plasmon Decay mode (LFTPD) ^dag is investigated in the regime in which the instability is not resonantly coupled to surface waves propagating along the boundary region. In this case, spatially dependent growth rate profiles and spatially dependent transit layer magnetic fields are reported. The regime is of interest because we have found that when the perturbation wavenumber parallel to the boundary is less than the pump frequency divided by twice

  17. Low-frequency oscillations at high density in JFT-2

    International Nuclear Information System (INIS)

    Maeno, Masaki; Katagiri, Masaki; Suzuki, Norio; Fujisawa, Noboru

    1977-12-01

    Low-frequency oscillations in a plasma were measured with magnetic probes and Si surface-barrier detectors, and behaviour of the high density plasmas was studied. The plasma current profile in the phase of decreasing density after the interruption of gas input is more peaked than during gas input. The introduction of hydrogen during a discharge results in a reduction of the impurities flux. The increase of density by fast gas input is limited with a negative voltage spike. Immediately before a negative voltage spike, oscillations of m=1,2 grow, leading to the spike. (auth.)

  18. 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

  19. Independent control of ion current and ion impact energy onto electrodes in dual frequency plasma devices

    International Nuclear Information System (INIS)

    Boyle, P C; Ellingboe, A R; Turner, M M

    2004-01-01

    Dual frequency capacitive discharges are designed to offer independent control of the flux and energy of ions impacting on an object immersed in a plasma. This is desirable in applications such as the processing of silicon wafers for microelectronics manufacturing. In such discharges, a low frequency component couples predominantly to the ions, while a high frequency component couples predominantly to electrons. Thus, the low frequency component controls the ion energy, while the high frequency component controls the plasma density. Clearly, this desired behaviour is not achieved for arbitrary configurations of the discharge, and in general one expects some unwanted coupling of ion flux and energy. In this paper we use computer simulations with the particle-in-cell method to show that the most important governing parameter is the ratio of the driving frequencies. If the ratio of the high and low frequencies is great enough, essentially independent control of the ion energy and flux is possible by manipulation of the high and low frequency power sources. Other operating parameters, such as pressure, discharge geometry, and absolute power, are of much less significance

  20. Low frequency electrostatic modes in a magnetized dusty plasma

    International Nuclear Information System (INIS)

    Salimullah, M.; Hassan, M.H.A.

    1991-09-01

    The dispersion properties of low frequency electrostatic modes in a dusty plasma in the presence of a static homogeneous magnetic field are examined. It is found that the presence of the dust particles and the static magnetic field have significant effects on the dispersion relations. For the parallel propagation the electrostatic mode is slightly modified by the magnetic field for the ion acoustic branch. A new longitudinal mode arises at the extreme low frequency limit, which is unaffected by the magnetic field for the parallel propagation. For the transverse propagation the ion acoustic mode is not affected by the magnetic field. However, the undamped extreme low frequency mode is significantly modified by the presence of the magnetic field for the propagation transverse to the direction of the magnetic field. (author). 23 refs

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

    Science.gov (United States)

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

    2016-06-21

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

  2. Cluster observations of high-frequency waves in the exterior cusp

    Directory of Open Access Journals (Sweden)

    Y. Khotyaintsev

    2004-07-01

    Full Text Available We study wave emissions, in the frequency range from above the lower hybrid frequency up to the plasma frequency, observed during one of the Cluster crossings of a high-beta exterior cusp region on 4 March 2003. Waves are localized near narrow current sheets with a thickness a few times the ion inertial length; currents are strong, of the order of 0.1-0.5μA/m2 (0.1-0.5mA/m2 when mapped to ionosphere. The high frequency part of the waves, frequencies above the electron-cyclotron frequency, is analyzed in more detail. These high frequency waves can be broad-band, can have spectral peaks at the plasma frequency or spectral peaks at frequencies below the plasma frequency. The strongest wave emissions usually have a spectral peak near the plasma frequency. The wave emission intensity and spectral character change on a very short time scale, of the order of 1s. The wave emissions with strong spectral peaks near the plasma frequency are usually seen on the edges of the narrow current sheets. The most probable generation mechanism of high frequency waves are electron beams via bump-on-tail or electron two-stream instability. Buneman and ion-acoustic instability can be excluded as a possible generation mechanism of waves. We suggest that high frequency waves are generated by electron beams propagating along the separatrices of the reconnection region.

  3. High beta plasma operation in a toroidal plasma producing device

    International Nuclear Information System (INIS)

    Clarke, J.F.

    1978-01-01

    A high beta plasma is produced in a plasma producing device of toroidal configuration by ohmic heating and auxiliary heating. The plasma pressure is continuously monitored and used in a control system to program the current in the poloidal field windings. Throughout the heating process, magnetic flux is conserved inside the plasma and the distortion of the flux surfaces drives a current in the plasma. As a consequence, the total current increases and the poloidal field windings are driven with an equal and opposing increasing current. The spatial distribution of the current in the poloidal field windings is determined by the plasma pressure. Plasma equilibrium is maintained thereby, and high temperature, high beta operation results

  4. A high current high frequency ions gun

    International Nuclear Information System (INIS)

    Coutant, J.; Prevot, F.; Vienet, R.

    1959-01-01

    A 10 mA protons gun has been developed for different purposes. The first part of the report studies the plasma production with a RF electromagnetic field. Then the ion extraction process is analysed with particular reference to space charge phenomena. The last part describes a three electrode electrostatic lens which focusses the beam. (author) [fr

  5. Diagnosis of Unmagnetized Plasma Electron Number Density and Electron-neutral Collision Frequency by Using Microwave

    International Nuclear Information System (INIS)

    Yuan Zhongcai; Shi Jiaming; Xu Bo

    2005-01-01

    The plasma diagnostic method using the transmission attenuation of microwaves at double frequencies (PDMUTAMDF) indicates that the frequency and the electron-neutral collision frequency of the plasma can be deduced by utilizing the transmission attenuation of microwaves at two neighboring frequencies in a non-magnetized plasma. Then the electron density can be obtained from the plasma frequency. The PDMUTAMDF is a simple method to diagnose the plasma indirectly. In this paper, the interaction of electromagnetic waves and the plasma is analyzed. Then, based on the attenuation and the phase shift of a microwave in the plasma, the principle of the PDMUTAMDF is presented. With the diagnostic method, the spatially mean electron density and electron collision frequency of the plasma can be obtained. This method is suitable for the elementary diagnosis of the atmospheric-pressure plasma

  6. High Frequency Components Recovery in Music Signals

    Directory of Open Access Journals (Sweden)

    V. Sebesta

    1999-04-01

    Full Text Available A new technique is presented which improves the subjective quality of band-limited music by recovery of high frequency components. Sequences of harmonics are found in the band-limited signal and these sequences are expanded to the high frequency band to estimate the lost part of spectrum. High frequency signal is generated to match this estimation and is added to the band-limited signal.

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

    Science.gov (United States)

    Cairns, Iver H.

    1994-01-01

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

  8. Nonlinear parametric phenomena in plasma during radio frequency heating in the ion cyclotron frequency range

    International Nuclear Information System (INIS)

    Stepanov, K.N.

    1996-01-01

    Parametric phenomena in plasma which occur due to varying electric fields with the ion cyclotron frequency are reviewed. Beam-like lower hybrid instability emerges in strong pumping fields provided that the transverse relative velocity of particles is larger than the ion thermal speed (υ Ti ). The resulting turbulence and the following numerous manifestations observed experimentally are addressed. The turbulence may prove important for experiments aimed at plasma production or radio frequency (RF) cleaning of metallic surfaces of vacuum chambers in stellarators, tokamaks and helicon devices. In contrast, for a weak field (U Ti ) the kinetic parametric instabilities of ion cyclotron oscillations arise due to electrons. The issues of the turbulence, mathematical modelling, its role in turbulent heating observed on the torsatron Uragan-3M, decay instabilities associated with ion cyclotron oscillations and the triggering of ion quasimodes are considered. (author)

  9. Radio frequency plasma nitriding of aluminium at higher power levels

    International Nuclear Information System (INIS)

    Gredelj, Sabina; Kumar, Sunil; Gerson, Andrea R.; Cavallaro, Giuseppe P.

    2006-01-01

    Nitriding of aluminium 2011 using a radio frequency plasma at higher power levels (500 and 700 W) and lower substrate temperature (500 deg. C) resulted in higher AlN/Al 2 O 3 ratios than obtained at 100 W and 575 deg. C. AlN/Al 2 O 3 ratios derived from X-ray photoelectron spectroscopic analysis (and corroborated by heavy ion elastic recoil time of flight spectrometry) for treatments preformed at 100 (575 deg. C), 500 (500 deg. C) and 700 W (500 deg. C) were 1.0, 1.5 and 3.3, respectively. Scanning electron microscopy revealed that plasma nitrided surfaces obtained at higher power levels exhibited much finer nodular morphology than obtained at 100 W

  10. Lightweight, high-frequency transformers

    Science.gov (United States)

    Schwarze, G. E.

    1983-01-01

    The 25-kVA space transformer was developed under contract by Thermal Technology Laboratory, Buffalo, N. Y. The NASA Lewis transformer technology program attempted to develop the baseline technology. For the 25-kVA transformer the input voltage was chosen as 200 V, the output voltage as 1500 V, the input voltage waveform as square wave, the duty cycle as continuous, the frequency range (within certain constraints) as 10 to 40 kHz, the operating temperatures as 85 deg. and 130 C, the baseplate temperature as 50 C, the equivalent leakage inductance as less than 10 micro-h, the operating environment as space, and the life expectancy as 10 years. Such a transformer can also be used for aircraft, ship and terrestrial applications.

  11. 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

  12. Parallel simulation of radio-frequency plasma discharges

    International Nuclear Information System (INIS)

    Fivaz, M.; Howling, A.; Ruegsegger, L.; Schwarzenbach, W.; Baeumle, B.

    1994-01-01

    The 1D Particle-In-Cell and Monte Carlo collision code XPDP1 is used to model radio-frequency argon plasma discharges. The code runs faster on a single-user parallel system called MUSIC than on a CRAY-YMP. The low cost of the MUSIC system allows a 24-hours-per-day use and the simulation results are available one to two orders of magnitude quicker than with a super computer shared with other users. The parallelization strategy and its implementation are discussed. Very good agreement is found between simulation results and measurements done in an experimental argon discharge. (author) 2 figs., 3 refs

  13. High plasma rotation velocity and density transitions by biased electrodes in RF produced, magnetized plasma

    International Nuclear Information System (INIS)

    Matsuyama, Shoichiro; Shinohara, Shunjiro

    2001-01-01

    A large density profile modification was successfully obtained by voltage biasing to electrodes inserted in a RF (radio frequency) produced, magnetized plasma, and formation of strong shear of azimuthal plasma rotation velocity in a supersonic regime was found. For the case of biasing to an electrode near the central plasma region, two types of density transitions were observed in the outer plasma region: one was an oscillatory transition between two states, and the other was a transition from high to low density states with a large reduction of density fluctuations. (author)

  14. High plasma rotation velocity and density transitions by biased electrodes in RF produced, magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Matsuyama, Shoichiro; Shinohara, Shunjiro [Kyushu Univ., Interdisciplinary Graduate School of Engineering Sciences, Fukuoka (Japan)

    2001-07-01

    A large density profile modification was successfully obtained by voltage biasing to electrodes inserted in a RF (radio frequency) produced, magnetized plasma, and formation of strong shear of azimuthal plasma rotation velocity in a supersonic regime was found. For the case of biasing to an electrode near the central plasma region, two types of density transitions were observed in the outer plasma region: one was an oscillatory transition between two states, and the other was a transition from high to low density states with a large reduction of density fluctuations. (author)

  15. High order harmonic generation from plasma mirror

    International Nuclear Information System (INIS)

    Thaury, C.

    2008-09-01

    When an intense laser beam is focused on a solid target, its surface is rapidly ionized and forms a dense plasma that reflects the incident field. For laser intensities above few 10 15 W/cm 2 , high order harmonics of the laser frequency, associated in the time domain to a train of atto-second pulses (1 as = 10 18 s), can be generated upon this reflection. Because such a plasma mirror can be used with arbitrarily high laser intensities, this process should eventually lead to the production of very intense pulses in the X-ray domain. In this thesis, we demonstrate that for laser intensities about 10 19 W/cm 2 , two mechanisms can contribute to the generation of high order harmonics: the coherent wake emission and the relativistic emission. These two mechanisms are studied both theoretically and experimentally. In particular, we show that, thanks to very different properties, the harmonics generated by these two processes can be unambiguously distinguished experimentally. We then investigate the phase properties of the harmonic, in the spectral and in the spatial domain. Finally, we illustrate how to exploit the coherence of the generation mechanisms to get information on the dynamics of the plasma electrons. (author)

  16. Foundations of High-Pressure Thermal Plasmas

    Science.gov (United States)

    Murphy, Anthony B.; Uhrlandt, Dirk

    2018-06-01

    An introduction to the main methods used to produce, model and measure thermal plasmas is provided, with emphasis on the differences between thermal plasmas and other types of processing plasmas. The critical properties of thermal plasmas are explained in physical terms and their importance in different applications is considered. The characteristics, and advantages and disadvantages, of the different main types of thermal plasmas (transferred and non-transferred arcs, radio-frequency inductively-coupled plasmas and microwave plasmas) are discussed. The methods by which flow is stabilized in arc plasmas are considered. The important concept of local thermodynamic equilibrium (LTE) is explained, leading into a discussion of the importance of thermophysical properties, and their calculation in LTE and two-temperature plasmas. The standard equations for modelling thermal plasmas are presented and contrasted with those used for non-equilibrium plasmas. Treatments of mixed-gas and non-LTE plasmas are considered, as well as the sheath regions adjacent to electrodes. Finally, the main methods used for electrical, optical, spectroscopic and laser diagnostics of thermal plasmas are briefly introduced, with an emphasis on the required assumptions for their reliable implementation, and the specific requirements of thermal plasmas.

  17. High frequency CARM driver for rf linacs

    International Nuclear Information System (INIS)

    Danly, B.G.

    1993-01-01

    This CARM program has successfully demonstrated the first ever long-pulse CARM oscillator operation; these results demonstrate the potential of CARMs as an alternative source of millimeter waves to the gyrotron for ECRH plasma heating. The result of 1.8 MW at 27.8 GHz and 0.5 μs pulse width in the TE 11 mode represent a clear demonstration of the capabilities of the CARM oscillator for the production of high powers with large frequency upshift. It is hoped that this successful proof-of-principle demonstration.will lead to further development of the CARM as an ECRH source by the DOE Office of Fusion Energy, Development and Technology Division. This success is a direct outcome of this support of the Advanced Energy Projects Office of DOE in the form of this program. The CARM amplifier component of the program, although unsuccessful at obtaining CARM amplifier operation at 17 GHz, has succeeded by furthering the understanding of the limitations and difficulties that lie ahead for continued CARM amplifier development. The amplifier component of the program has successfully demonstrated a high power second and third harmonic gyro-TWT amplifier. Up to 5 MW of power at 17.1 GHz and >50dB gain have been obtained. These results should be viewed as an important contribution of this program to the development of viable microwave sources for powering the next linear collider. Indeed, the present gyro-amplifier, which resulted from this program, is presently being used in ongoing high-gradient accelerator research at MIT under a DOE High Energy Physics grant. As a result of both the oscillator and amplifier advances made during this program, the CARM and harmonic gyro-TWT have reached a significantly more mature level; their future role in specific applications of benefit to DOEs OFE and HEP offices may now be pursued

  18. Low frequency waves in streaming quantum dusty plasmas

    Science.gov (United States)

    Rozina, Ch.; Jamil, M.; Khan, Arroj A.; Zeba, I.; Saman, J.

    2017-09-01

    The influence of quantum effects on the excitation of two instabilities, namely quantum dust-acoustic and quantum dust-lower-hybrid waves due to the free streaming of ion/dust particles in uniformly magnetized dusty plasmas has been investigated using a quantum hydrodynamic model. We have obtained dispersion relations under some particular conditions applied on streaming ions and two contrastreaming dust particle beams at equilibrium and have analyzed the growth rates graphically. We have shown that with the increase of both the electron number density and the streaming speed of ion there is enhancement in the instability due to the fact that the dense plasma particle system with more energetic species having a high speed results in the increase of the growth rate in the electrostatic mode. The application of this work has been pointed out for laboratory as well as for space dusty plasmas.

  19. Improved Frequency Fluctuation Model for Spectral Line Shape Calculations in Fusion Plasmas

    International Nuclear Information System (INIS)

    Ferri, S.; Calisti, A.; Mosse, C.; Talin, B.; Lisitsa, V.

    2010-01-01

    A very fast method to calculate spectral line shapes emitted by plasmas accounting for charge particle dynamics and effects of an external magnetic field is proposed. This method relies on a new formulation of the Frequency Fluctuation Model (FFM), which yields to an expression of the dynamic line profile as a functional of the static distribution function of frequencies. This highly efficient formalism, not limited to hydrogen-like systems, allows to calculate pure Stark and Stark-Zeeman line shapes for a wide range of density, temperature and magnetic field values, which is of importance in plasma physics and astrophysics. Various applications of this method are presented for conditions related to fusion plasmas.

  20. High-beta plasma blobs in the morningside plasma sheet

    Directory of Open Access Journals (Sweden)

    G. Haerendel

    1999-12-01

    Full Text Available Equator-S frequently encountered, i.e. on 30% of the orbits between 1 March and 17 April 1998, strong variations of the magnetic field strength of typically 5–15-min duration outside about 9RE during the late-night/early-morning hours. Very high-plasma beta values were found, varying between 1 and 10 or more. Close conjunctions between Equator-S and Geotail revealed the spatial structure of these "plasma blobs" and their lifetime. They are typically 5–10° wide in longitude and have an antisymmetric plasma or magnetic pressure distribution with respect to the equator, while being altogether low-latitude phenomena  (≤ 15°. They drift slowly sunward, exchange plasma across the equator and have a lifetime of at least 15–30 min. While their spatial structure may be due to some sort of mirror instability, little is known about the origin of the high-beta plasma. It is speculated that the morningside boundary layer somewhat further tailward may be the source of this plasma. This would be consistent with the preference of the plasma blobs to occur during quiet conditions, although they are also found during substorm periods. The relation to auroral phenomena in the morningside oval is uncertain. The energy deposition may be mostly too weak to generate a visible signature. However, patchy aurora remains a candidate for more disturbed periods.Key words. Magnetospheric physics (plasma convection; plasma sheet; plasma waves and instabilities

  1. Preface to Special Topic: Advances in Radio Frequency Physics in Fusion Plasmas

    International Nuclear Information System (INIS)

    Tuccillo, Angelo A.; Ceccuzzi, Silvio; Phillips, Cynthia K.

    2014-01-01

    It has long been recognized that auxiliary plasma heating will be required to achieve the high temperature, high density conditions within a magnetically confined plasma in which a fusion “burn” may be sustained by copious fusion reactions. Consequently, the application of radio and microwave frequency electromagnetic waves to magnetically confined plasma, commonly referred to as RF, has been a major part of the program almost since its inception in the 1950s. These RF waves provide heating, current drive, plasma profile control, and Magnetohydrodynamics (MHD) stabilization. Fusion experiments employ electromagnetic radiation in a wide range of frequencies, from tens of MHz to hundreds of GHz. The fusion devices containing the plasma are typically tori, axisymmetric or non, in which the equilibrium magnetic fields are composed of a strong toroidal magnetic field generated by external coils, and a poloidal field created, at least in the symmetric configurations, by currents flowing in the plasma. The waves are excited in the peripheral regions of the plasma, by specially designed launching structures, and subsequently propagate into the core regions, where resonant wave-plasma interactions produce localized heating or other modification of the local equilibrium profiles. Experimental studies coupled with the development of theoretical models and advanced simulation codes over the past 40+ years have led to an unprecedented understanding of the physics of RF heating and current drive in the core of magnetic fusion devices. Nevertheless, there are serious gaps in our knowledge base that continue to have a negative impact on the success of ongoing experiments and that must be resolved as the program progresses to the next generation devices and ultimately to “demo” and “fusion power plant.” A serious gap, at least in the ion cyclotron (IC) range of frequencies and partially in the lower hybrid frequency ranges, is the difficulty in coupling large amount of

  2. Preface to Special Topic: Advances in Radio Frequency Physics in Fusion Plasmas

    Science.gov (United States)

    Tuccillo, Angelo A.; Phillips, Cynthia K.; Ceccuzzi, Silvio

    2014-06-01

    It has long been recognized that auxiliary plasma heating will be required to achieve the high temperature, high density conditions within a magnetically confined plasma in which a fusion "burn" may be sustained by copious fusion reactions. Consequently, the application of radio and microwave frequency electromagnetic waves to magnetically confined plasma, commonly referred to as RF, has been a major part of the program almost since its inception in the 1950s. These RF waves provide heating, current drive, plasma profile control, and Magnetohydrodynamics (MHD) stabilization. Fusion experiments employ electromagnetic radiation in a wide range of frequencies, from tens of MHz to hundreds of GHz. The fusion devices containing the plasma are typically tori, axisymmetric or non, in which the equilibrium magnetic fields are composed of a strong toroidal magnetic field generated by external coils, and a poloidal field created, at least in the symmetric configurations, by currents flowing in the plasma. The waves are excited in the peripheral regions of the plasma, by specially designed launching structures, and subsequently propagate into the core regions, where resonant wave-plasma interactions produce localized heating or other modification of the local equilibrium profiles. Experimental studies coupled with the development of theoretical models and advanced simulation codes over the past 40+ years have led to an unprecedented understanding of the physics of RF heating and current drive in the core of magnetic fusion devices. Nevertheless, there are serious gaps in our knowledge base that continue to have a negative impact on the success of ongoing experiments and that must be resolved as the program progresses to the next generation devices and ultimately to "demo" and "fusion power plant." A serious gap, at least in the ion cyclotron (IC) range of frequencies and partially in the lower hybrid frequency ranges, is the difficulty in coupling large amount of power to the

  3. Very high plasma switches. Basic plasma physics and switch technology

    International Nuclear Information System (INIS)

    Doucet, H.J.; Roche, M.; Buzzi, J.M.

    1988-01-01

    A review of some high power switches recently developed for very high power technology is made with a special attention to the aspects of plasma physics involved in the mechanisms, which determine the limits of the possible switching parameters

  4. Turbulence of high-beta plasma

    International Nuclear Information System (INIS)

    Khvesyuk, V.I.; Chirkov, A.Y.

    1999-01-01

    Principals of numerical modelling of turbulence in high-beta plasma (β > 0.1) are discussed. Creation of transport model for axial symmetric nonuniform confining magnetic field is considered. Numerical model of plasma turbulence in FRC is presented. The physical and mathematical models are formulated from nonuniform axial symmetric high-beta plasma. It is shown that influence of waves arise under this plasma conditions lead to chaotic motion of charged particles across magnetic field. (author)

  5. Cooking Appliances Using High-Frequency Heating

    OpenAIRE

    木村, 秀行; Hideyuki, KIMURA; (株)日立製作所機械研究所

    2007-01-01

    We have produced a guide suitable for people with no technical knowledge of cooking appliances that use high-frequency heating. In general, cooking appliances that use an electric heat source are popular since, they are simple to use because the offer easy heat control, are safe because they do not have naked flames, and do not make kitchens dirty because there is no exhaust. In recent years, high-efficiency cooking appliances using high-frequency heating technology have surged in popularity....

  6. High frequency oscillations in brain hemodynamic response

    Science.gov (United States)

    Akin, Ata; Bolay, Hayrunnisa

    2007-07-01

    Tight autoregulation of vessel tone guarantees proper delivery of nutrients to the tissues. This regulation is maintained at a more delicate level in the brain since any decrease in the supply of glucose and oxygen to neuronal tissues might lead to unrecoverable injury. Functional near infrared spectroscopy has been proposed as a new tool to monitor the cerebrovascular response during cognitive activity. We have observed that during a Stroop task three distinct oscillatory patterns govern the control of the cerebrovascular reactivity: very low frequency (0.02-0.05 Hz), low frequency (0.08-0.12 Hz) and high frequency (0.12-0.18 Hz). High frequency oscillations have been shown to be related to stress level of the subjects. Our findings indicate that as the stress level is increased so does the energy of the high frequency component indicating a higher stimulation from the autonomic nervous system.

  7. High order harmonic generation from plasma mirrors

    International Nuclear Information System (INIS)

    George, H.

    2010-01-01

    When an intense laser beam is focused on a solid target, the target's surface is rapidly ionized and forms dense plasma that reflects the incident field. For laser intensities above few 10 to the power of 15 Wcm -2 , high order harmonics of the laser frequency, associated in the time domain to a train of atto-second pulses (1 as 10 -18 s), can be generated upon this reflection. In this thesis, we developed numerical tools to reveal original aspects of harmonic generation mechanisms in three different interaction regime: the coherent wake emission, the relativistic emission and the resonant absorption. In particular, we established the role of these mechanisms when the target is a very thin foil (thickness of the order of 100 nm). Then we study experimentally the spectral, spatial and coherence properties of the emitted light. We illustrate how to exploit these measurements to get information on the plasma mirror dynamics on the femtosecond and atto-second time scales. Last, we propose a technique for the single-shot complete characterization of the temporal structure of the harmonic light emission from the laser-plasma mirror interaction. (author)

  8. 75 FR 81284 - Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology; Draft...

    Science.gov (United States)

    2010-12-27

    ... Frequency and Ultra High Frequency Active SONAR Technology; Draft Programmatic Environmental Assessment and... Programmatic Environmental Assessment (PEA) for the Nationwide Use of High Frequency (HF) and Ultra High... potential impacts of each alternative on the human and natural environments. DATES: Comments and related...

  9. High frequency dynamics in centrifugal compressors

    NARCIS (Netherlands)

    Twerda, A.; Meulendijks, D.; Smeulers, J.P.M.; Handel, R. van den; Lier, L.J. van

    2008-01-01

    Problems with centrifugal compressors relating to high frequency, i.e. Blade passing frequency (BPF) are increasing. Pulsations and vibrations generated in centrifugal compressors can lead to nuisance, due to strong tonal noise, and even breakdown. In several cases the root cause of a failure or a

  10. High-frequency electrodeless plasmatrons and their application in chemistry and material engineering

    International Nuclear Information System (INIS)

    Czernichowska, A.; Jurewicz, J.

    1975-01-01

    An apparatus used to obtain high frequency induction-coupled type plasma was described with regard to the working chamber design, methods employed for stabilization of plasma, types of working gases, operating conditions such as pressure, plasmatron power rating, diameter of plasma stream and its temperature. The methods of high frequency discharge ignition, inductor design as well as the requirements to be satisfied by the generators employed for excitation of high frequency electrodeless plasma were briefly discussed. A number of applications of high frequency electrodeless plasma were mentioned such as monocrystal growing, excitation of spectra in the optical spectroscopy, spheroidization of powders and other processes with particular emphasis on chemical reactions. A review of plasmotron designs was also made. (author)

  11. Generation of sheet currents by high frequency fast MHD waves

    Energy Technology Data Exchange (ETDEWEB)

    Núñez, Manuel, E-mail: mnjmhd@am.uva.es

    2016-07-01

    The evolution of fast magnetosonic waves of high frequency propagating into an axisymmetric equilibrium plasma is studied. By using the methods of weakly nonlinear geometrical optics, it is shown that the perturbation travels in the equatorial plane while satisfying a transport equation which enables us to predict the time and location of formation of shock waves. For plasmas of large magnetic Prandtl number, this would result into the creation of sheet currents which may give rise to magnetic reconnection and destruction of the original equilibrium. - Highlights: • Regular solutions of quasilinear hyperbolic systems may evolve into shocks. • The shock location is found for high frequency fast MHD waves. • The result is applied to static axisymmetric equilibria. • The previous process may lead to the formation of sheet currents and destruction of the equilibrium.

  12. Low frequency RF heating of plasmas in a toroidal stellarator

    International Nuclear Information System (INIS)

    Golovato, S.N.

    1977-01-01

    Studies of transit-time magnetic pumping and Alfven wave heating have been done in the Proto-Cleo stellarator. Both plasma heating and plasma confinement have been investigated. A traveling wave was launched around the Proto-Cleo l = 2, 6 field period stellarator to attempt transit-time magnetic pumping of a pulsed electron beam moving along the magnetic field lines. An apparent loss of the beam was seen when the transit-time magnetic pumping was applied. A random walk diffusion of the beam electrons with a step size determined by the radial EXB drift due to the poloidal electric field agrees well with the experimental results. Alfven wave heating was applied to plasmas in the Proto-Cleo l = 3, 7 field period stellarator. Global excitation of Alfven waves was accomplished by exciting an electrostatically shielded helical winding corresponding to a q = 3 rational field line with a pulsed, high-power RF source. Theoretical analysis of this helical wave launcher predicted effective energy absorption in the Proto-Cleo gun-produced plasma

  13. Superconducting high frequency high power resonators

    International Nuclear Information System (INIS)

    Hobbis, C.; Vardiman, R.; Weinman, L.

    1974-01-01

    A niobium superconducting quarter-wave helical resonator has been designed and built. The resonator has been electron-beam welded and electropolished to produce a smooth flaw-free surface. This has been followed by an anodization to produce a 1000 A layer of Nb 2 0 5 . At the resonant frequency of approximately 15 MHz the unloaded Q was approximately equal to 4.6x10 6 with minimal dielectric support. With the resonator open to the helium bath to provide cooling, and rigidly supported by a teflon cylinder, 350 V of power were transferred at a doubly loaded Q of 3500. The extrapolation of the results to a Qsub(DL) of 1000 meet the power handling criteria of one kilowatt for the intended application. (author)

  14. Effect of suprathermal electrons on the intensity and Doppler frequency of electron plasma lines

    Directory of Open Access Journals (Sweden)

    P. Guio

    Full Text Available In an incoherent scattering radar experiment, the spectral measurement of the so-called up- and downshifted electron plasma lines provides information about their intensity and their Doppler frequency. These two spectral lines correspond, in the backscatter geometry, to two Langmuir waves travelling towards and away from the radar. In the daytime ionosphere, the presence of a small percentage of photoelectrons produced by the solar EUV of the total electron population can excite or damp these Langmuir waves above the thermal equilibrium, resulting in an enhancement of the intensity of the lines above the thermal level. The presence of photo-electrons also modifies the dielectric response function of the plasma from the Maxwellian and thus influences the Doppler frequency of the plasma lines. In this paper, we present a high time-resolution plasma-line data set collected on the Eiscat VHF radar. The analysed data are compared with a model that includes the effect of a suprathermal electron population calculated by a transport code. By comparing the intensity of the analysed plasma lines data to our model, we show that two sharp peaks in the electron suprathermal distribution in the energy range 20-30 eV causes an increased Landau damping around 24.25 eV and 26.25 eV. We have identified these two sharp peaks as the effect of the photoionisation of N2 and O by the intense flux of monochromatic HeII radiation of wavelength 30.378 nm (40.812 eV created in the chromospheric network and coronal holes. Furthermore, we see that what would have been interpreted as a mean Doppler drift velocity for a Maxwellian plasma is actually a shift of the Doppler frequency of the plasma lines due to suprathermal electrons.

    Key words. Ionosphere (electric fields and currents; solar radiation and cosmic ray effects

  15. Effect of suprathermal electrons on the intensity and Doppler frequency of electron plasma lines

    Directory of Open Access Journals (Sweden)

    P. Guio

    1999-07-01

    Full Text Available In an incoherent scattering radar experiment, the spectral measurement of the so-called up- and downshifted electron plasma lines provides information about their intensity and their Doppler frequency. These two spectral lines correspond, in the backscatter geometry, to two Langmuir waves travelling towards and away from the radar. In the daytime ionosphere, the presence of a small percentage of photoelectrons produced by the solar EUV of the total electron population can excite or damp these Langmuir waves above the thermal equilibrium, resulting in an enhancement of the intensity of the lines above the thermal level. The presence of photo-electrons also modifies the dielectric response function of the plasma from the Maxwellian and thus influences the Doppler frequency of the plasma lines. In this paper, we present a high time-resolution plasma-line data set collected on the Eiscat VHF radar. The analysed data are compared with a model that includes the effect of a suprathermal electron population calculated by a transport code. By comparing the intensity of the analysed plasma lines data to our model, we show that two sharp peaks in the electron suprathermal distribution in the energy range 20-30 eV causes an increased Landau damping around 24.25 eV and 26.25 eV. We have identified these two sharp peaks as the effect of the photoionisation of N2 and O by the intense flux of monochromatic HeII radiation of wavelength 30.378 nm (40.812 eV created in the chromospheric network and coronal holes. Furthermore, we see that what would have been interpreted as a mean Doppler drift velocity for a Maxwellian plasma is actually a shift of the Doppler frequency of the plasma lines due to suprathermal electrons.Key words. Ionosphere (electric fields and currents; solar radiation and cosmic ray effects

  16. Mechanism for plasma waves at the harmonics of the plasma frequency in the electron foreshock boundary

    International Nuclear Information System (INIS)

    Klimas, A.J.

    1983-01-01

    A bump-on-tail unstable reduced velocity distribution has been constructed from data obtained at the upstream boundary of the electron foreshock by the GSFC electron spectrometer experiment on the ISEE 1 satellite. This distribution is used as the initial plasma state for a numerical integration of the one-dimensional Vlasov-Maxwell system of equations. The integration is carried through the growth of the instability, beyond its saturation, and well into the stabilized plasma regime. A power spectrum for the electric field of the stabilized plasma is computed. The spectrum is dominated by a narrow peak at the Bohm-Gross frequency of the unstable field mode but it also contain significant power at the harmonics of the Bohm-Gross frequency. The harmonic power is in sharp peaks which are split into closely spaced doublets. The fundamental peak at the Bohm-Gross frequency is also split, in this case into a closely space triplet. The fundamental peak at the Bohm-Gross frequency is also split, in this case into a closely space triplet. The splitting is due to slow modulations of the stabilized electric field oscillations which, it is thought, are caused by wave-particle trapping. The wavelength of mth harmonic of the Bohm-Gross frequency is given by lambda/sub u//m, where lambda/sub u/ is the wavelength of the unstable mode. The mechanism for excitation of the second harmonic is shwn to be second-order wave-wave coupling which takes place during that period in the evolution of the instability which would otherwise be called the linear growth phase. It is conjectured that the higher harmonics are excited by the same mechanism. It is further argued that harmonic excitation at the boundary of the electron foreshock should be a common occurrence

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

    Science.gov (United States)

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

    2016-09-01

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

  18. Overview of the Advanced High Frequency Branch

    Science.gov (United States)

    Miranda, Felix A.

    2015-01-01

    This presentation provides an overview of the competencies, selected areas of research and technology development activities, and current external collaborative efforts of the NASA Glenn Research Center's Advanced High Frequency Branch.

  19. Nanostructures for Very High Frequency Electronics

    National Research Council Canada - National Science Library

    Gelmont, Boris

    2002-01-01

    The study of a new class of mesoscopic high frequency semi-conductor devices based on resonant tunneling in staggered-bandgap heterostructures with III-V semi-conductor ternary alloys such as AlGaSb...

  20. Radio-frequency plasma nitriding and nitrogen plasma immersion ion implantation of Ti-6Al-4V alloy

    International Nuclear Information System (INIS)

    Wang, S.Y.; Chu, P.K.; Tang, B.Y.; Zeng, X.C.; Wang, X.F.; Chen, Y.B.

    1997-01-01

    Nitrogen ion implantation improves the wear resistance of Ti-6Al-4V alloys by forming a hard TiN superficial passivation layer. However, the thickness of the layer formed by traditional ion implantation is typically 100-200 nm and may not be adequate for many industrial applications. We propose to use radio-frequency (RF) plasma nitriding and nitrogen plasma immersion ion implantation (PIII) to increase the layer thickness. By using a newly designed inductively coupled RF plasma source and applying a series of negative high voltage pulses to the Ti-6Al-4V samples. RF plasma nitriding and nitrogen PIII can be achieved. Our process yields a substantially thicker modified layer exhibiting more superior wear resistance characteristics, as demonstrated by data from micro-hardness testing, pin-on-disc wear testing, scanning electron microscopy (SEM), as well as Auger electron spectroscopy (AES). The performance of our newly developed inductively coupled RF plasma source which is responsible for the success of the experiments is also described. (orig.)

  1. High frequency system project implementation plan

    International Nuclear Information System (INIS)

    Moon, L.L.

    1976-01-01

    The High Frequency System is a new mobile, digital diagnostic recording system for use at the Nevada Test Site. Many different kinds of event data will be digitized in real-time by this system, and these data will be recorded and stored for later read-out and transmission to NADCEN. The hardware and software requirements of the High Frequency System are examined, and the parameters of the system are proposed

  2. Modeling of physical processes in radio-frequency plasma thrusters

    OpenAIRE

    Tian, Bin

    2017-01-01

    This Thesis presents an investigation of the plasma-wave interaction in Helicon Plasma Thrusters (HPT). The HPT is a new concept of electric space propulsion, which generates plasmas with RF heating and provides thrust by the electrodeless acceleration of plasmas in a magnetic nozzle. An in-depth and extensive literature review of the state of the art of the models and experiments of plasma-wave interaction in helicon plasma sources and thrusters is carried out. Then, a theoret...

  3. High-vacuum plasma pump

    International Nuclear Information System (INIS)

    Dorodnov, A.M.; Minajchev, V.E.; Miroshkin, S.I.

    1980-01-01

    The action of an electric-arc high-vacuum pump intended for evacuating the volumes in which the operation processes are followed by a high gas evolution is considered. The operation of the pump is based on the principle of controlling the getter feed according to the gas load and effect of plasma sorbtion pumping. The pump performances are given. The starting pressure is about 5 Pa, the limiting residual pressure is about 5x10 -6 Pa, the pumping out rate of nitrogen in the pressure range 5x10 -5 -5x10 -3 Pa accounts for about 4000 l/s, the power consumption comes to 6 kW. Analyzing the results of the test operation of the pump, it has been concluded that its principal advantages are the high starting pressure, controlled getter feed rate and possibility of pumping out the gases which are usually pumped out with difficulty. The operation reliability of the pump is defined mainly by reliable operation of the ignition system of the vacuum arc [ru

  4. RF plasma production and heating below ion-cyclotron frequencies in Uragan torsatrons

    International Nuclear Information System (INIS)

    Moiseenko, V.E.; Berezhnyj, V.L.; Bondarenko, V.N.; Burchenko, P.Ya.; Chechkin, V.V.; Chernyshenko, V.Ya.; Dreval, M.B.; Garkusha, I.E.; Glazunov, G.P.; Grigor'eva, L.I.; Konovalov, V.G.; Kotsubanov, V.D.; Kramskoi, Ye.D.; Kulaga, A.E.; Lozin, A.V.; Castejon, F.; Hidalgo, C.; Hartmann, D.; Koch, R.; Lyssoivan, A.I.

    2011-01-01

    In the IPP-Kharkiv there are two torsatrons (stellarators) in operation, and in both of them Alfven resonance heating under high-k || conditions is used. This method of heating is advantageous for small-size devices, since in contrast to the minority and second-harmonic heating it can be realized at lower plasma densities. A series of experiments has been performed at the Uragan-3M torsatron with an aim to investigate the features of the discharge with a three-half-turn antenna. Electron temperatures in the T-bar = 0.2-0.5 keV range are achieved at plasma densities n-bar e approx. (0.5-1.5) x 10 13 cm -3 . The plasma energy content has increased by a factor of 2 with respect to the plasma produced with the frame antenna. A new four-strap shielded antenna has been manufactured and installed in the Uragan-2M. A high-frequency discharge for wall conditioning is introduced in the Uragan-2M torsatron. The discharge is sustained by a specially designed small frame antenna, and efficient hydrogen dissociation is achieved. A self-consistent model has been developed for simulation of plasma production in ICRF. The model includes a set of particle and energy-balance equations for the electrons, and the boundary problem for the Maxwell equations. The first calculation results on RF plasma production in the Uragan-2M stellarator with the frame-type antenna are presented.

  5. High frequency conductivity in carbon nanotubes

    Directory of Open Access Journals (Sweden)

    S. S. Abukari

    2012-12-01

    Full Text Available We report on theoretical analysis of high frequency conductivity in carbon nanotubes. Using the kinetic equation with constant relaxation time, an analytical expression for the complex conductivity is obtained. The real part of the complex conductivity is initially negative at zero frequency and become more negative with increasing frequency, until it reaches a resonance minimum at ω ∼ ωB for metallic zigzag CNs and ω < ωB for armchair CNs. This resonance enhancement is indicative for terahertz gain without the formation of current instabilities induced by negative dc conductivity. We noted that due to the high density of states of conduction electrons in metallic zigzag carbon nanotubes and the specific dispersion law inherent in hexagonal crystalline structure result in a uniquely high frequency conductivity than the corresponding values for metallic armchair carbon nanotubes. We suggest that this phenomenon can be used to suppress current instabilities that are normally associated with a negative dc differential conductivity.

  6. Characteristics of ceramic oxide nanoparticles synthesized using radio frequency produced thermal plasma

    International Nuclear Information System (INIS)

    Dhamale, Gayatri D.; Mathe, V.L.; Bhoraskar, S.V.; Ghorui, S.

    2015-01-01

    Thermal plasma devices with their unique processing capabilities due to extremely high temperature and steep temperature gradient play an important role in synthesis of ultrafine powders in the range of 100nm or less. High temperature gas phase synthesis in Radio Frequency (RF) thermal plasma reactor is an attractive route for mass production of refractory nanoparticles, especially in the case of rare earth oxides. Here we report synthesis of Yttrium Oxide (Y_2O_3), Neodymium Oxide (Nd_2O_3) and Aluminum Oxide (Al_2O_3) in an inductively coupled radio frequency thermal plasma reactor. Synthesized nanoparticles find wide application in various fields like gate dielectrics, photocatalytic applications, laser devices and photonics. Nano sized Yttrium oxide, Neodymium Oxide and Aluminum oxide powders were separately synthesized in an RF plasma reactor starting with micron sized irregular shaped precursor powders. The system was operated at 3MHz in atmospheric pressure at different power levels. Synthesized powders were scrapped out from different deposition locations inside the reactor and characterized for their phase, morphology, particle size, crystallinity and other characteristic features. Highly crystalline nature of the synthesized particles, narrow size distribution, location dependent phase formation, and distinct variation in the inherent defect states compared to the bulk are some of the important characteristic features observed

  7. The effect of plasma etching on the surface topography of niobium superconducting radio frequency cavities

    Science.gov (United States)

    Radjenović, B.; Radmilović-Radjenović, M.

    2014-11-01

    In this letter the evolution of the surface topography of a niobium superconducting radio frequency cavity caused by different plasma etching modes (isotropic and anisotropic) is studied by the three-dimensional level set method. The initial rough surface is generated starting from an experimental power spectral density. The time dependence of the rms roughness is analyzed and the growth exponential factors β are determined for two etching modes (isotropic and anisotropic) assuming that isotropic etching is a much more effective mechanism of smoothing. The obtained simulation results could be useful for optimizing the parameters of the etching processes needed to obtain high quality niobium surfaces for superconducting radio frequency cavities.

  8. Extremely high frequency RF effects on electronics.

    Energy Technology Data Exchange (ETDEWEB)

    Loubriel, Guillermo Manuel; Vigliano, David; Coleman, Phillip Dale; Williams, Jeffery Thomas; Wouters, Gregg A.; Bacon, Larry Donald; Mar, Alan

    2012-01-01

    The objective of this work was to understand the fundamental physics of extremely high frequency RF effects on electronics. To accomplish this objective, we produced models, conducted simulations, and performed measurements to identify the mechanisms of effects as frequency increases into the millimeter-wave regime. Our purpose was to answer the questions, 'What are the tradeoffs between coupling, transmission losses, and device responses as frequency increases?', and, 'How high in frequency do effects on electronic systems continue to occur?' Using full wave electromagnetics codes and a transmission-line/circuit code, we investigated how extremely high-frequency RF propagates on wires and printed circuit board traces. We investigated both field-to-wire coupling and direct illumination of printed circuit boards to determine the significant mechanisms for inducing currents at device terminals. We measured coupling to wires and attenuation along wires for comparison to the simulations, looking at plane-wave coupling as it launches modes onto single and multiconductor structures. We simulated the response of discrete and integrated circuit semiconductor devices to those high-frequency currents and voltages, using SGFramework, the open-source General-purpose Semiconductor Simulator (gss), and Sandia's Charon semiconductor device physics codes. This report documents our findings.

  9. High-beta plasma blobs in the morningside plasma sheet

    Directory of Open Access Journals (Sweden)

    G. Haerendel

    Full Text Available Equator-S frequently encountered, i.e. on 30% of the orbits between 1 March and 17 April 1998, strong variations of the magnetic field strength of typically 5–15-min duration outside about 9RE during the late-night/early-morning hours. Very high-plasma beta values were found, varying between 1 and 10 or more. Close conjunctions between Equator-S and Geotail revealed the spatial structure of these "plasma blobs" and their lifetime. They are typically 5–10° wide in longitude and have an antisymmetric plasma or magnetic pressure distribution with respect to the equator, while being altogether low-latitude phenomena 
    (≤ 15°. They drift slowly sunward, exchange plasma across the equator and have a lifetime of at least 15–30 min. While their spatial structure may be due to some sort of mirror instability, little is known about the origin of the high-beta plasma. It is speculated that the morningside boundary layer somewhat further tailward may be the source of this plasma. This would be consistent with the preference of the plasma blobs to occur during quiet conditions, although they are also found during substorm periods. The relation to auroral phenomena in the morningside oval is uncertain. The energy deposition may be mostly too weak to generate a visible signature. However, patchy aurora remains a candidate for more disturbed periods.

    Key words. Magnetospheric physics (plasma convection; plasma sheet; plasma waves and instabilities

  10. Electron energy distributions and excitation rates in high-frequency argon discharges

    International Nuclear Information System (INIS)

    Ferreira, C.M.; Loureiro, J.

    1983-06-01

    The electron energy distribution functions and rate coefficients for excitation and ionisation in argon under the action of an uniform high-frequency electric field were calculated by numerically solving the homogeneous Boltzmann equation. Analytic calculations in the limiting cases ω>>νsub(c) and ω<<νsub(c), where ω is the wave angular frequency and νsub(c) is the electron-neutral collision frequency for momentum transfer, are also presented and shown to be in very good agreement with the numerical computations. The results reported here are relevant for the modelling of high-frequency discharges in argon and, in particular, for improving recent theoretical descriptions of a plasma column sustained by surface microwaves. The properties of surface wave produced plasmas make them interesting as possible substitutes for other more conventional plasma sources for such important applications as plasma chemistry laser excitation, plasma etching spectroscopic sources etc...

  11. Influence of the matrix composition in the Emission spectroscopic analysis of solutions with continuous nebulization of the sample and excitation of the spectrum in a high-frequency inductively coupled plasma discharge

    International Nuclear Information System (INIS)

    Zil'bershtein, K.I.; Kartasheva, M.A.; Mushkovich, G.N.

    1986-01-01

    Numerous investigations have shown that the emission spectroscopic analysis of solutions with the use of a high-frequency inductively coupled plasma discharge is characterized by the absence of an influence or the presence of a small influence of the matrix elements on the amplitudes of the analytical signals of the elements being determined and, consequently, on the results of an analysis. The influences of the first type include the influences of easily ionized elements, which, as we know, are very significant in spectroscopic analysis with the use of traditional sources for the excitation of the spectra (arcs, sparks, and flames). The influences of the second type include, in particular, the influences associated with changes in the viscosity and surface tension of the solutions as the concentration of the matrix elements in the solutions is increased. In order to obtain correct results from an analysis in the case of spectral interference, special methods for treating the spectra are used for the purpose of taking into account the background and the instances of superposition and establishing the true (''pure'') intensity of the analytical lines. Results are shown of the Determination of impurities in aqueous solutions of sodium Molybate Single Crystals (the concentration of Na 2 Mo 2 O 7 in the solution was 1 mg/ml). When the solutions being analyzed are diluted to a concentration of Na 2 Mo 2 O 7 equal to 1 mg/ml, good agreement between the results of the determination of vanadium (and other impurities) obtained with the use of reference solutions not containing the matrix elements and the results obtained with the use of reference solutions containing the matrix elements in the same concentrations as in the solutions being analyzed (1mg/ml) was guaranteed

  12. High-Frequency Percussive Ventilation Revisited

    Science.gov (United States)

    2010-01-01

    be implemented. ‡ Follow the reverse of the ventilation sequence if respiratory alkalosis develops—however, start at ventilation goal sequence 1 not at...High-frequency percussive ventilation (HFPV) has demonstrated a potential role as a rescue option for refractory acute respiratory distress syndrome...frequency percussive ventilation (HFPV) has demon- strated a potential role as a salvage option for refrac- tory acute respiratory distress syndrome

  13. Atomic processes in high temperature plasmas

    International Nuclear Information System (INIS)

    Hahn, Y.

    1990-03-01

    Much theoretical and experimental efforts have been expended in recent years to study those atomic processes which are specially relevant to understanding high temperature laboratory plasmas. For magnetically confined fusion plasmas, the temperature range of interest spans from the hundreds of eV at plasma edges to 10 keV at the center of the plasma, where most of the impurity ions are nearly fully ionized. These highly stripped ions interact strongly with electrons in the plasma, leading to further excitation and ionization of the ions, as well as electron capture. Radiations are emitted during these processes, which easily escape to plasma container walls, thus cooling the plasma. One of the dominant modes of radiation emission has been identified with dielectronic recombination. This paper reviews this work

  14. Role of Radio Frequency and Microwaves in Magnetic Fusion Plasma Research

    Directory of Open Access Journals (Sweden)

    Hyeon K. Park

    2017-10-01

    Full Text Available The role of electromagnetic (EM waves in magnetic fusion plasma—ranging from radio frequency (RF to microwaves—has been extremely important, and understanding of EM wave propagation and related technology in this field has significantly advanced magnetic fusion plasma research. Auxiliary heating and current drive systems, aided by various forms of high-power RF and microwave sources, have contributed to achieving the required steady-state operation of plasmas with high temperatures (i.e., up to approximately 10 keV; 1 eV = 10000 K that are suitable for future fusion reactors. Here, various resonance values and cut-off characteristics of wave propagation in plasmas with a nonuniform magnetic field are used to optimize the efficiency of heating and current drive systems. In diagnostic applications, passive emissions and active sources in this frequency range are used to measure plasma parameters and dynamics; in particular, measurements of electron cyclotron emissions (ECEs provide profile information regarding electron temperature. Recent developments in state-of-the-art 2D microwave imaging systems that measure fluctuations in electron temperature and density are largely based on ECE. The scattering process, phase delays, reflection/diffraction, and the polarization of actively launched EM waves provide us with the physics of magnetohydrodynamic instabilities and transport physics.

  15. High Frequency Traders and Market Structure

    NARCIS (Netherlands)

    Menkveld, A.J.

    2014-01-01

    The arrival of high-frequency traders (HFTs) coincided with the entry of new markets and, subsequently, strong fragmentation of the order flow. These trends might be related as new markets serve HFTs who seek low fees and high speed. New markets only thrive on competitive price quotes that

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

    International Nuclear Information System (INIS)

    Hopkins, Mark A.; King, Lyon B.

    2014-01-01

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

  17. 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

  18. High-frequency and microwave circuit design

    CERN Document Server

    Nelson, Charles

    2007-01-01

    An integral part of any communications system, high-frequency and microwave design stimulates major progress in the wireless world and continues to serve as a foundation for the commercial wireless products we use every day. The exceptional pace of advancement in developing these systems stipulates that engineers be well versed in multiple areas of electronics engineering. With more illustrations, examples, and worked problems, High-Frequency and Microwave Circuit Design, Second Edition provides engineers with a diverse body of knowledge they can use to meet the needs of this rapidly progressi

  19. High frequency and pulse scattering physical acoustics

    CERN Document Server

    Pierce, Allan D

    1992-01-01

    High Frequency and Pulse Scattering investigates high frequency and pulse scattering, with emphasis on the phenomenon of echoes from objects. Geometrical and catastrophe optics methods in scattering are discussed, along with the scattering of sound pulses and the ringing of target resonances. Caustics and associated diffraction catastrophes are also examined.Comprised of two chapters, this volume begins with a detailed account of geometrically based approximation methods in scattering theory, focusing on waves transmitted through fluid and elastic scatterers and glory scattering; surface ray r

  20. New aspects of high energy density plasma

    International Nuclear Information System (INIS)

    Hotta, Eiki

    2005-10-01

    The papers presented at the symposium on 'New aspects of high energy density plasma' held at National Institute for Fusion Science are collected in this proceedings. The papers reflect the present status and recent progress in the experiments and theoretical works on high energy density plasma produced by pulsed power technology. The 13 of the presented papers are indexed individually. (J.P.N.)

  1. Transverse ion energization and low-frequency plasma waves in the mid-altitude auroral zone: A case study

    International Nuclear Information System (INIS)

    Peterson, W.K.; Shelley, E.G.; Boardsen, S.A.; Gurnett, D.A.; Ledley, B.G.; Sugiura, M.; Moore, T.E.; Waite, J.H.

    1988-01-01

    The transport of ions from the ionosphere to the magnetosphere requires that ions acquire significant energy in directions both transverse and parallel to the magnetic field. There is a considerable body of experimental evidence that shows that transverse energization occurs over a wide range of altitudes on auroral field lines. Many recent analytical and simulation studies have addressed the microphysics involved in transverse ion energization. There are, however, remarkably few published high-resolution plasma and plasma wave observations obtained in the mid-altitude auroral region available to compare with the analytical and simulation studies. Several hundred hours of high-resolution plasma data obtained from the Dynamics Explorer 1 satellite have been surveyed. A wide variety of plasma environments that are difficult to simply characterize were found. We present here a comprehensive set of high-sensitivity, high-resolution plasma wave, ion, and magnetometer data obtained from an evening auroral zone crossing at r/R/sub E/∼3. The total density, thermal structure, and composition of the plasma in this representative interval varied rapidly, as did the character (mode) of low-frequency plasma waves observed. We did not find an unambiguous particle and wave signature of local transverse ion energization, but we did frequently find intervals where local transverse ion heating was consistent with the observations. We also found a downward flowing ion distribution that occurred simultaneously with a region of intense plasma wave emissions primarily below the lower hybrid resonance frequency. copyright American Geophysical Union 1988

  2. Dust removal in radio-frequency plasmas by a traveling potential modulation

    International Nuclear Information System (INIS)

    Li Yangfang; Jiang Ke; Thomas, Hubertus M.; Morfill, Gregor E.

    2010-01-01

    The dust contamination in plasma deposition processes plays a crucial role in the quality and the yield of the products. To improve the quality and the yield of plasma processing, a favorable way is to remove the dust particles actively from the plasma reactors.Our recent experiments in the striped electrode device show that a traveling plasma modulation allows for a systematic particle removal independent of the reactor size. Besides the rf powered electrode, the striped electrode device includes a segmented electrode that consists of 100 electrically insulated narrow stripes. A traveling potential profile is produced by the modulation of the voltage signals applied on the stripes. The dust particles are trapped in the potential wells and transported with the traveling of the potential profile.The particle-in-cell (PIC) simulation on the potential above the segmented electrode indicates that the traveling potential profile can be realized either by applying low-frequency (0.1-10 Hz) voltage signals with a fixed phase shift between adjacent stripes or high-frequency (10 kHz a circumflex AS 100 MHz) signals with the amplitudes modulated by a low-frequency envelope. The transportation of the dust particles is simulated with a two-dimensional molecular dynamics (MD) code with the potential profile obtained from the PIC simulation. The MD results reproduce the experimental observations successfully.This technology allows for an active removal of the contaminating particles in processing plasmas and it is independent of the reactor size. The removal velocity is controllable by adjusting the parameters for the modulation.

  3. Rf-biasing of highly idealized plasmas

    NARCIS (Netherlands)

    Westermann, R.H.J.; Blauw, M.A.; Goedheer, W.J.; Sanden, van de M.C.M.; Schmidt, J.; Simek, M.; Pekarek, S.; Prukner, V.

    2007-01-01

    Remote plasmas, which are subjected to a radio-frequency (RF) biased surface, have been investigated theoretically and experimentally for decades. The relation between the complex power (DC) voltage characteristics, the ion energy distribution and control losses of the ion bombardment are of

  4. Plasma instabilities in high electric fields

    DEFF Research Database (Denmark)

    Morawetz, K.; Jauho, Antti-Pekka

    1994-01-01

    expression is derived for the nonequilibrium dielectric function epsilon(K, omega). For certain values of momenta K and frequency omega, Imepsilon(K, omega) becomes negative, implying a plasma instability. This new instability exists only for strong electric fields, underlining its nonequilibrium origin....

  5. Dry friction damping couple at high frequencies

    Czech Academy of Sciences Publication Activity Database

    Půst, Ladislav; Pešek, Luděk; Košina, Jan; Radolfová, Alena

    2014-01-01

    Roč. 8, č. 1 (2014), s. 91-100 ISSN 1802-680X Institutional support: RVO:61388998 Keywords : dry friction * damping * high frequencies Subject RIV: BI - Acoustics http://www.kme.zcu.cz/acm/acm/article/view/239/265

  6. High Frequency Trading, Information, and Takeovers

    NARCIS (Netherlands)

    Humphery-Jenner, M.

    2011-01-01

    This paper (1) proposes new variables to detect informed high-frequency trading (HFT), (2) shows that HFT can help to predict takeover targets, and (3) shows that HFT in uences target announcement announcement returns. Prior literature suggests that informed trade may occur before takeovers, but has

  7. Essays on high frequency financial econometrics

    NARCIS (Netherlands)

    Yang, X.

    2015-01-01

    It has long been demonstrated that continuous-time methods are powerful tools in financial modeling. Yet only in recent years, their counterparts in empirical analysis—high frequency econometrics—began to emerge with the availability of intra-day data and relevant statistical tools. This

  8. Analytical and numerical study of a gaseous plasma dipole in the UHF frequency band

    NARCIS (Netherlands)

    Melazzi, Davide; Lancellotti, Vito; Capobianco, Antonio Daniele

    2017-01-01

    Gaseous plasma antennas are appealing in applications in which reconfigurability is desired, because the radiation properties can be changed by tuning the plasma parameters. In this paper, an analytical and numerical analysis of a gaseous plasma dipole that works in the 0.3-3 GHz frequency range is

  9. A theoretical study of hot plasma spheroids in the presence of low-frequency electromagnetic waves

    Science.gov (United States)

    Ahmadizadeh, Y.; Jazi, B.; Barjesteh, S.

    2016-07-01

    While taking into account thermal motion of electrons, scattering of electromagnetic waves with low frequency from hot plasma spheroids is investigated. In this theoretical research, ions are heavy to respond to electromagnetic fluctuations. The solution of scalar wave equation in spheroidal coordinates for electric potential inside the plasma spheroids are obtained. The variations of resonance frequencies vs. Debye length are studied and consistency between the obtained results in this paper and the results for the well-known plasma objects such as plasma column and spherical plasma have been proved.

  10. Structured waves near the plasma frequency observed in three auroral rocket flights

    Directory of Open Access Journals (Sweden)

    M. Samara

    2006-11-01

    Full Text Available We present observations of waves at and just above the plasma frequency (fpe from three high frequency electric field experiments on three recent rockets launched to altitudes of 300–900 km in active aurora. The predominant observed HF waves just above fpe are narrowband, short-lived emissions with amplitudes ranging from <1 mV/m to 20 mV/m, often associated with structured electron density. The nature of these HF waves, as determined from frequency-time spectrograms, is highly variable: in some cases, the frequency decreases monotonically with time as in the "HF-chirps" previously reported (McAdams and LaBelle, 1999, but in other cases rising frequencies are observed, or features which alternately rise and fall in frequency. They exhibit two timescales of amplitude variation: a short timescale, typically 50–100 ms, associated with individual discrete features, and a longer timescale associated with the general decrease in the amplitudes of the emissions as the rocket moves away from where the condition f~fpe holds. The latter timescale ranges from 0.6 to 6.0 s, corresponding to distances of 2–7 km, assuming the phenomenon to be stationary and using the rocket velocity to convert time to distance.

  11. Structured waves near the plasma frequency observed in three auroral rocket flights

    Directory of Open Access Journals (Sweden)

    M. Samara

    2006-11-01

    Full Text Available We present observations of waves at and just above the plasma frequency (fpe from three high frequency electric field experiments on three recent rockets launched to altitudes of 300–900 km in active aurora. The predominant observed HF waves just above fpe are narrowband, short-lived emissions with amplitudes ranging from <1 mV/m to 20 mV/m, often associated with structured electron density. The nature of these HF waves, as determined from frequency-time spectrograms, is highly variable: in some cases, the frequency decreases monotonically with time as in the "HF-chirps" previously reported (McAdams and LaBelle, 1999, but in other cases rising frequencies are observed, or features which alternately rise and fall in frequency. They exhibit two timescales of amplitude variation: a short timescale, typically 50–100 ms, associated with individual discrete features, and a longer timescale associated with the general decrease in the amplitudes of the emissions as the rocket moves away from where the condition f~fpe holds. The latter timescale ranges from 0.6 to 6.0 s, corresponding to distances of 2–7 km, assuming the phenomenon to be stationary and using the rocket velocity to convert time to distance.

  12. Modeling Plasma Formation in a Micro-gap at Microwave Frequency

    Science.gov (United States)

    Bowman, Arthur; Remillard, Stephen

    2013-03-01

    In the presence of a strong electric field, gas molecules become ionized, forming a plasma. The study of this dielectric breakdown at microwave frequency has important applications in improving the operation of radio frequency (RF) devices, where the high electric fields present in small gaps can easily ionize gases like air. A cone and tuner resonant structure was used to induce breakdown of diatomic Nitrogen in adjustable micro-gaps ranging from 13 to 1,156 μm. The electric field for plasma formation exhibited strong pressure dependence in the larger gap sizes, as predicted by previous theoretical and experimental work. Pressure is proportional to the frequency of collision between electrons and molecules, which increases with pressure when the gap is large, but levels off in the micro-gap region. A separate model of the breakdown electric field based on the characteristic diffusion length of the plasma also fit the data poorly for these smaller gap sizes. This may be explained by a hypothesis that dielectric breakdown at and below the 100 μm gap size occurs outside the gap, an argument that is supported by the observation of very high breakdown threshold electric fields in this region. Optical emissions revealed that vibrational and rotational molecular transitions of the first positive electronic system are suppressed in micro-gaps, indicating that transitions into the molecular ground state do not occur in micro-gap plasmas. Acknowledgements: National Science Foundation under NSF-REU Grant No. PHY/DMR-1004811, the Provost's Office of Hope College, and the Hope College Division of Natural and Applied Sciences.

  13. Control of Reactive Species Generated by Low-frequency Biased Nanosecond Pulse Discharge in Atmospheric Pressure Plasma Effluent

    Science.gov (United States)

    Takashima, Keisuke; Kaneko, Toshiro

    2016-09-01

    The control of hydroxyl radical and the other gas phase species generation in the ejected gas through air plasma (air plasma effluent) has been experimentally studied, which is a key to extend the range of plasma treatment. Nanosecond pulse discharge is known to produce high reduced electric field (E/N) discharge that leads to efficient generation of the reactive species than conventional low frequency discharge, while the charge-voltage cycle in the low frequency discharge is known to be well-controlled. In this study, the nanosecond pulse discharge biased with AC low frequency high voltage is used to take advantages of these discharges, which allows us to modulate the reactive species composition in the air plasma effluent. The utilization of the gas-liquid interface and the liquid phase chemical reactions between the modulated long-lived reactive species delivered from the air plasma effluent could realize efficient liquid phase chemical reactions leading to short-lived reactive species production far from the air plasma, which is crucial for some plasma agricultural applications.

  14. Evolution of Very High Frequency Power Supplies

    DEFF Research Database (Denmark)

    Knott, Arnold; Andersen, Toke Meyer; Kamby, Peter

    2013-01-01

    The ongoing demand for smaller and lighter power supplies is driving the motivation to increase the switching frequencies of power converters. Drastic increases however come along with new challenges, namely the increase of switching losses in all components. The application of power circuits used...... in radio frequency transmission equipment helps to overcome those. However those circuits were not designed to meet the same requirements as power converters. This paper summarizes the contributions in recent years in application of very high frequency (VHF) technologies in power electronics, shows results...... of the recent advances and describes the remaining challenges. The presented results include a self-oscillating gate-drive, air core inductor optimizations, an offline LED driver with a power density of 8.9 W/cm3 and a 120 MHz, 9 W DC powered LED driver with 89 % efficiency as well as a bidirectional VHF...

  15. Influence of radio frequency waves on the interchange stability in HANBIT mirror plasmas

    International Nuclear Information System (INIS)

    Hogun Jhang; Kim, S.S.; Lee, S.G.; Park, B.H.; Bak, J.G.

    2005-01-01

    Experimental and theoretical studies are made of the influence of high frequency radio frequency (rf) waves upon interchange stability in HANBIT mirror plasmas. An emphasis is put on the interchange stability near the resonance region, ω 0 ∼Ω i , where ω 0 is the angular frequency of the applied rf wave and Ω i is the ion cyclotron frequency. Recent HANBIT experiments have shown the existence of the interchange-stable operation window in favor of ω 0 /Ω i ≤1 with its sensitivity on the applied rf power. A strong nonlinear interaction between the rf wave and the interchange mode has been observed with the generation of sideband waves. A theoretical analysis including both the ponderomotive force and the nonlinear sideband wave coupling has been developed and applied to the interpretation of the experiments, resulting in a good agreement. From the study, it is concluded that the nonlinear wave-wave coupling process is responsible for the rf stabilization of the interchange modes in HANBIT mirror plasmas operating near the resonance condition. (author)

  16. High-frequency strontium vapor laser for biomedical applications

    Science.gov (United States)

    Hvorostovsky, A.; Kolmakov, E.; Kudashev, I.; Redka, D.; Kancer, A.; Kustikova, M.; Bykovskaya, E.; Mayurova, A.; Stupnikov, A.; Ruzankina, J.; Tsvetkov, K.; Lukyanov, N.; Paklinov, N.

    2018-02-01

    Sr-laser with high pulse repetition rate and high peak radiation power is a unique tool for studying rapidly occurring processes in time (plasma diagnostics, photoablation, etc.). In addition, the study of the frequency characteristics of the active medium of the laser helps to reveal the physics of the formation of an inverse medium in metal vapor lasers. In this paper, an experimental study of an Sr-laser with an active volume of 5.8 cm3 in the pulse repetition frequency range from 25 to 200 kHz is carried out, and a comparison with the frequency characteristics of media with large active volumes is given. We considered the frequency characteristics of the active medium in two modes: at a constant energy in the excitation pulse CU2 / 2 and at a constant average power consumed by the rectifier. In the presented work with a small-volume GRT using the TASITR-5/12 TASITRON switch, a laser was generated for Pairs of strontium at a CSF of 200 kHz. The behavior of the characteristics of the generation lines of 6.456 μm, 1 μm, and 3 μm at increased repetition frequencies is considered. Using the example of large-volume GRT, it is shown that tubes with a large active volume increase their energy characteristics with the growth of the CSF. The possibility of laser operation at pulse repetition rates above 200 kHz is shown.

  17. Radio-frequency oxygen-plasma-enhanced pulsed laser deposition of IGZO films

    Directory of Open Access Journals (Sweden)

    Chia-Man Chou

    2017-07-01

    Full Text Available We demonstrate the crystalline structures, optical transmittance, surface and cross-sectional morphologies, chemical compositions, and electrical properties of indium gallium zinc oxide (IGZO-based thin films deposited on glass and silicon substrates through pulsed laser deposition (PLD incorporated with radio-frequency (r.f.-generated oxygen plasma. The plasma-enhanced pulsed laser deposition (PEPLD-based IGZO thin films exhibited a c-axis-aligned crystalline (CAAC structure, which was attributed to the increase in Zn-O under high oxygen vapor pressure (150 mTorr. High oxygen vapor pressure (150 mTorr and low r.f. power (10 W are the optimal deposition conditions for fabricating IGZO thin films with improved electrical properties.

  18. Radio-frequency oxygen-plasma-enhanced pulsed laser deposition of IGZO films

    Science.gov (United States)

    Chou, Chia-Man; Lai, Chih-Chang; Chang, Chih-Wei; Wen, Kai-Shin; Hsiao, Vincent K. S.

    2017-07-01

    We demonstrate the crystalline structures, optical transmittance, surface and cross-sectional morphologies, chemical compositions, and electrical properties of indium gallium zinc oxide (IGZO)-based thin films deposited on glass and silicon substrates through pulsed laser deposition (PLD) incorporated with radio-frequency (r.f.)-generated oxygen plasma. The plasma-enhanced pulsed laser deposition (PEPLD)-based IGZO thin films exhibited a c-axis-aligned crystalline (CAAC) structure, which was attributed to the increase in Zn-O under high oxygen vapor pressure (150 mTorr). High oxygen vapor pressure (150 mTorr) and low r.f. power (10 W) are the optimal deposition conditions for fabricating IGZO thin films with improved electrical properties.

  19. Dense high-temperature plasma transport processes

    International Nuclear Information System (INIS)

    Giniyatova, Sh.G.

    2002-01-01

    In this work the transport processes in dense high-temperature semiclassical plasma are studied on the base of the kinetic equation, where the semiclassical potential was used, in its collision integral. The coefficient of plasma electrical conductivity, viscosity and thermal conductivity were received. There were compared with the other authors' results. The Grad's method was used obtaining of viscosity and thermal coefficients. (author)

  20. Nonlinear radiation of waves at combination frequencies due to radiation-surface wave interaction in plasmas

    International Nuclear Information System (INIS)

    El Naggar, I.A.; Hussein, A.M.; Khalil, Sh.M.

    1992-09-01

    Electromagnetic waves radiated with combination frequencies from a semi-bounded plasma due to nonlinear interaction of radiation with surface wave (both of P-polarization) has been investigated. Waves are radiated both into vacuum and plasma are found to be P-polarized. We take into consideration the continuity at the plasma boundary of the tangential components of the electric field of the waves. The case of normal incidence of radiation and rarefield plasma layer is also studied. (author). 7 refs

  1. Space and phase resolved ion energy and angular distributions in single- and dual-frequency capacitively coupled plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yiting; Kushner, Mark J. [Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, Michigan 48109-2122 (United States); Moore, Nathaniel; Pribyl, Patrick; Gekelman, Walter [Department of Physics, University of California, Los Angeles, California 90095 (United States)

    2013-11-15

    The control of ion energy and angular distributions (IEADs) is critically important for anisotropic etching or deposition in microelectronic fabrication processes. With single frequency capacitively coupled plasmas (CCPs), the narrowing in angle and spread in energy of ions as they cross the sheath are definable functions of frequency, sheath width, and mean free path. With increases in wafer size, single frequency CCPs are finding difficulty in meeting the requirement of simultaneously controlling plasma densities, ion fluxes, and ion energies. Dual-frequency CCPs are being investigated to provide this flexible control. The high frequency (HF) is intended to control the plasma density and ion fluxes, while the ion energies are intended to be controlled by the low frequency (LF). However, recent research has shown that the LF can also influence the magnitude of ion fluxes and that IEADs are determined by both frequencies. Hence, separate control of fluxes and IEADs is complex. In this paper, results from a two-dimensional computational investigation of Ar/O{sub 2} plasma properties in an industrial reactor are discussed. The IEADs are tracked as a function of height above the substrate and phase within the rf cycles from the bulk plasma to the presheath and through the sheath with the goal of providing insights to this complexity. Comparison is made to laser-induced fluorescence experiments. The authors found that the ratios of HF/LF voltage and driving frequency are critical parameters in determining the shape of the IEADs, both during the transit of the ion through the sheath and when ions are incident onto the substrate. To the degree that contributions from the HF can modify plasma density, sheath potential, and sheath thickness, this may provide additional control for the IEADs.

  2. Resonator as high frequency electromagnetic field oscillation generator

    International Nuclear Information System (INIS)

    Svoroba, O.V.; Scherbina, V.O.

    2007-01-01

    The problem of finding the u(x-vector) field potential in a specific waveguide with generalized corrugated core geometry is considered. The perturbation is brought to the system by high energy electron beam, injected in a waveguide. It is shown that the Neumann spectral problem can be reduced to finding Green approximation solution, and how it can be solved by the discretization technique. Considered parameterization allow to optimize the u(x-vector) field for specific frequency tuning. This method can be used as plasma heating method for thermonuclear temperature control

  3. High-frequency Rayleigh-wave method

    Science.gov (United States)

    Xia, J.; Miller, R.D.; Xu, Y.; Luo, Y.; Chen, C.; Liu, J.; Ivanov, J.; Zeng, C.

    2009-01-01

    High-frequency (???2 Hz) Rayleigh-wave data acquired with a multichannel recording system have been utilized to determine shear (S)-wave velocities in near-surface geophysics since the early 1980s. This overview article discusses the main research results of high-frequency surface-wave techniques achieved by research groups at the Kansas Geological Survey and China University of Geosciences in the last 15 years. The multichannel analysis of surface wave (MASW) method is a non-invasive acoustic approach to estimate near-surface S-wave velocity. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that simultaneous inversion with higher modes and the fundamental mode can increase model resolution and an investigation depth. The other important seismic property, quality factor (Q), can also be estimated with the MASW method by inverting attenuation coefficients of Rayleigh waves. An inverted model (S-wave velocity or Q) obtained using a damped least-squares method can be assessed by an optimal damping vector in a vicinity of the inverted model determined by an objective function, which is the trace of a weighted sum of model-resolution and model-covariance matrices. Current developments include modeling high-frequency Rayleigh-waves in near-surface media, which builds a foundation for shallow seismic or Rayleigh-wave inversion in the time-offset domain; imaging dispersive energy with high resolution in the frequency-velocity domain and possibly with data in an arbitrary acquisition geometry, which opens a door for 3D surface-wave techniques; and successfully separating surface-wave modes, which provides a valuable tool to perform S-wave velocity profiling with high-horizontal resolution. ?? China University of Geosciences (Wuhan) and Springer-Verlag GmbH 2009.

  4. High-Order Frequency-Locked Loops

    DEFF Research Database (Denmark)

    Golestan, Saeed; Guerrero, Josep M.; Quintero, Juan Carlos Vasquez

    2017-01-01

    In very recent years, some attempts for designing high-order frequency-locked loops (FLLs) have been made. Nevertheless, the advantages and disadvantages of these structures, particularly in comparison with a standard FLL and high-order phase-locked loops (PLLs), are rather unclear. This lack...... study, and its small-signal modeling, stability analysis, and parameter tuning are presented. Finally, to gain insight about advantages and disadvantages of high-order FLLs, a theoretical and experimental performance comparison between the designed second-order FLL and a standard FLL (first-order FLL...

  5. Design and development of ITER high-frequency magnetic sensor

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Y., E-mail: Yunxing.Ma@iter.org [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); Fircroft Engineering, Lingley House, 120 Birchwood Point, Birchwood Boulevard, Warrington, WA3 7QH (United Kingdom); Vayakis, G. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); Begrambekov, L.B. [National Research Nuclear University (MEPhI), 115409, Moscow, Kashirskoe shosse 31 (Russian Federation); Cooper, J.-J. [Culham Centre for Fusion Energy (CCFE), Abingdon, Oxfordshire OX14 3DB (United Kingdom); Duran, I. [IPP Prague, Za Slovankou 1782/3, 182 00 Prague 8 (Czech Republic); Hirsch, M.; Laqua, H.P. [Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, Wendelsteinstraße 1, D-17491 Greifswald (Germany); Moreau, Ph. [CEA Cadarache, 13108 Saint Paul lez Durance Cedex (France); Oosterbeek, J.W. [Eindhoven University of Technology (TU/e), PO Box 513, 5600 MB Eindhoven (Netherlands); Spuig, P. [CEA Cadarache, 13108 Saint Paul lez Durance Cedex (France); Stange, T. [Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, Wendelsteinstraße 1, D-17491 Greifswald (Germany); Walsh, M. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France)

    2016-11-15

    Highlights: • ITER high-frequency magnetic sensor system has been designed. • Prototypes have been successfully manufactured. • Manufactured prototypes have been tested in various labs. • Test results experimentally validated the design. - Abstract: High-frequency (HF) inductive magnetic sensors are the primary ITER diagnostic set for Toroidal Alfvén Eigenmodes (TAE) detection, while they also supplement low-frequency MHD and plasma equilibrium measurements. These sensors will be installed on the inner surface of ITER vacuum vessel, operated in a harsh environment with considerable neutron/nuclear radiation and high thermal load. Essential components of the HF sensor system, including inductive coil, electron cyclotron heating (ECH) shield, electrical cabling and termination load, have been designed to meet ITER measurement requirements. System performance (e.g. frequency response, thermal conduction) has been assessed. A prototyping campaign was initiated to demonstrate the manufacturability of the designed components. Prototypes have been produced according to the specifications. A series of lab tests have been performed to examine assembly issues and validate electrical and thermo-mechanical aspects of the design. In-situ microwave radiation test has been conducted in the MISTRAL test facility at IPP-Greifswald to experimentally examine the microwave shielding efficiency and structural integrity of the ECH shield. Low-power microwave attenuation measurement and scanning electron microscopic inspection were conducted to probe and examine the quality of the metal coating on the ECH shield.

  6. Low-frequency fluctuations in a pure toroidal magnetized plasma

    Indian Academy of Sciences (India)

    A magnetized, low- plasma in pure toroidal configuration is formed and extensively studied with ion mass as control parameter. Xenon, krypton and argon plasmas are formed at a fixed toroidal magnetic field of 0.024 T, with a peak density of ∼ 1011 cm-3, ∼ 4 × 1010 cm-3 and ∼ 2 × 1010 cm−3 respectively.

  7. High Temperature, High Frequency Fuel Metering Valve, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Active Signal Technologies and its subcontractor Moog propose to develop a high-frequency actuator driven valve intended to achieve TRL 6 by the end of Phase II....

  8. Stabilizing effects of hot electrons on low frequency plasma drift waves

    International Nuclear Information System (INIS)

    Huang Chaosong; Qiu Lijian; Ren Zhaoxing

    1988-01-01

    The MHD equation is used to study the stabilization of low frequency drift waves driven by density gradient of plasma in a hot electron plasma. The dispersion relation is derived, and the stabilizing effects of hot electrons are discussed. The physical mechanism for hot electron stabilization of the low frequency plasma perturbations is charge uncovering due to the hot electron component, which depends only on α, the ratio of N h /N i , but not on the value of β h . The hot electrons can reduce the growth rate of the interchange mode and drift wave driven by the plasma, and suppress the enomalous plasma transport caused by the drift wave. Without including the effectof β h , the stabilization of the interchange mode requires α≅2%, and the stabilization of the drift wave requires α≅40%. The theoretical analyses predict that the drift wave is the most dangerous low frequency instability in the hot electron plasma

  9. Ionospheric heating with oblique high-frequency waves

    International Nuclear Information System (INIS)

    Field, E.C. Jr.; Bloom, R.M.; Kossey, P.A.

    1990-01-01

    This paper presents calculations of ionospheric electron temperature and density perturbations and ground-level signal changes produced by intense oblique high-frequency (HF) radio waves. The analysis takes into account focusing at caustics, the consequent Joule heating of the surrounding plasma, heat conduction, diffusion, and recombination processes, these being the effects of a powerful oblique modifying wave. It neglects whatever plasma instabilities might occur. The authors then seek effects on a secondary test wave that is propagated along the same path as the first. The calculations predict ground-level field strength reductions of several decibels in the test wave for modifying waves having effective radiated power (ERP) in the 85- to 90-dBW range. These field strength changes are similar in sign, magnitude, and location to ones measured in Soviet experiments. The location of the signal change is sensitive to the frequency and the model ionosphere assumed; so future experiments should employ the widest possible range of frequencies and propagation conditions. An ERP of 90 dBW seems to be a sort of threshold that, if exceeded, might result in substantial rather than small signal changes. The conclusions are based solely on Joule heating and subsequent refraction of waves passing through caustic regions

  10. 78 FR 70567 - Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology; Final...

    Science.gov (United States)

    2013-11-26

    ... Frequency and Ultra High Frequency Active SONAR Technology; Final Programmatic Environmental Assessment and... each alternative on the human and natural environments. FOR FURTHER INFORMATION CONTACT: If you have... Programmatic Environmental Assessment The scope of the PEA focuses on potential impacts associated with the...

  11. 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

  12. Radio frequency plasma heating in large tokamak systems near the lower hybrid resonance

    International Nuclear Information System (INIS)

    Deitz, A.; Hooke, W.M.

    1975-01-01

    The frequency range, power, efficiency, and pulse length of a high power rf system are discussed as they might be applied to the TFTR Tokamak facility as well as on a full scale reactor. Comparisons are made of the size, power output, and costs to obtain microwave power sufficient to satisfy the physics requirements. A new microwave feed concept is discussed which will improve the coupling of the microwave energy into the plasma. The unique advantages of waveguide feed systems is apparent when one considers the practical problems associated with coupling supplementary heating energy into a reactor

  13. Investigation of low-frequency fluctuations in the edge plasma of ASDEX

    Energy Technology Data Exchange (ETDEWEB)

    Rudyj, A; Carlson, A; Giannone, L.; Niedermeyer, H [Max-Planck-Institut fuer Plasmaphysik, Garching (Germany, F.R.); Bengtson, R D; Ritz, Ch P [Texas Univ., Austin, TX (USA); Kraemer, M [Bochum Univ. (Germany, F.R.); Tsois, N [NRS Demokritos, Attiki (Greece)

    1989-01-01

    Density fluctuations in the edge plasma of tokamaks in the frequency range up to a few 100 kHz have been reported for many years. The fluctuations are easily observed with Langmuir probes and are also visible in the H/sub {alpha}/ emission at locations with sufficient neutral gas density. High speed cine films taken on ASDEX show fluctuating stripes aligned approximately parallel to the magnetic field. It has been shown that these fluctuations, which are electrostatic, cause a major part if not all of the particle transport at the plasma edge. The mechanism driving these instabilities is however not yet clear. Langmuir probe measurements and optical observations were performed on ASDEX and a comparison was made with magnetic fluctuation measurements in order to further clarify the mechanism responsible for the edge turbulence. 5 refs., 3 figs.

  14. Investigation of low-frequency fluctuations in the edge plasma of ASDEX

    International Nuclear Information System (INIS)

    Rudyj, A.; Carlson, A.; Giannone, L.; Niedermeyer, H.; Bengtson, R.D.; Ritz, Ch.P.; Kraemer, M.; Tsois, N.

    1989-01-01

    Density fluctuations in the edge plasma of tokamaks in the frequency range up to a few 100 kHz have been reported for many years. The fluctuations are easily observed with Langmuir probes and are also visible in the H α emission at locations with sufficient neutral gas density. High speed cine films taken on ASDEX show fluctuating stripes aligned approximately parallel to the magnetic field. It has been shown that these fluctuations, which are electrostatic, cause a major part if not all of the particle transport at the plasma edge. The mechanism driving these instabilities is however not yet clear. Langmuir probe measurements and optical observations were performed on ASDEX and a comparison was made with magnetic fluctuation measurements in order to further clarify the mechanism responsible for the edge turbulence. 5 refs., 3 figs

  15. Inverter design for high frequency power distribution

    Science.gov (United States)

    King, R. J.

    1985-01-01

    A class of simple resonantly commutated inverters are investigated for use in a high power (100 KW - 1000 KW) high frequency (10 KHz - 20 KHz) AC power distribution system. The Mapham inverter is found to provide a unique combination of large thyristor turn-off angle and good utilization factor, much better than an alternate 'current-fed' inverter. The effects of loading the Mapham inverter entirely with rectifier loads are investigated by simulation and with an experimental 3 KW 20 KHz inverter. This inverter is found to be well suited to a power system with heavy rectifier loading.

  16. Calculation of the resonance frequency change for a cavity charged by a plasma with or without a static magnetic field

    International Nuclear Information System (INIS)

    Melin, G.

    1967-03-01

    In the mere case of a cold plasma with or without static magnetic field, are given two methods of calculation of resonance frequency shift and absorption in a cylindrical cavity crossed by a plasma column: 1. A perturbation method, already known and used for electronic density measurements is restated and its application is used for several high frequency cavity modes. 2. An exact method employing Maxwell's equations, which however necessitates a computer, is compared with the first one; it permits a determination of the validity limits of the perturbation method and to draw conclusions, [fr

  17. Dynamic shear stabilization of hydromagnetic instabilities in low-beta plasma column by a frequency near the ion cyclotron frequency

    International Nuclear Information System (INIS)

    Minami, Kazuo; Sato, Kazunori.

    1978-09-01

    The dynamic shear stabilization of the hydromagnetic instability in low-beta plasmas by an axial RF current whose frequency is not much smaller than the ion cyclotron frequency ωsub(ci) is analyzed in some detail. We adopt the simple model of a uniform plasma column with infinite conductivity. Attention is limited to the case of the m = 1 kink mode with long wave lengths. The Mathieu equation, in which the effect of the ion cyclotron motion is taken into account, is derived. It is shown that the dynamic shear stabilization is still effective, even if the frequency of the applied RF current is of the order of ωsub(ci), which is considerably higher than the frequencies believed to be available in the previous analyses. (author)

  18. Plasma inhomogeneities near the electrodes of a capacitively-coupled radio-frequency discharge containing dust particles

    Science.gov (United States)

    Tawidian, H.; Mikikian, M.; Couëdel, L.; Lecas, T.

    2011-11-01

    Small plasma spheroids are evidenced and analyzed in front of the electrodes of a capacitively-coupled radio-frequency discharge in which dust particles are growing. These regions are characterized by a spherical shape, a slightly enhanced luminosity and are related to instabilities induced by the presence of dust particles. Several types of behaviors are identified and particularly their chaotic appearance or disappearance and their rotational motion along the electrode periphery. Correlations with the unstable behavior of the global plasma glow are performed. These analyses are obtained thanks to high-speed imaging which is the only diagnostics able to evidence these plasma spheroids.

  19. Advances in Very High Frequency Power Conversion

    DEFF Research Database (Denmark)

    Kovacevic, Milovan

    Resonant and quasi-resonant converters operated at frequencies above 30 MHz have attracted special attention in the last two decades. Compared to conventional converters operated at ~100 kHz, they offer significant advantages: smaller volume and weight, lower cost, and faster transient performance....... Excellent performance and small size of magnetic components and capacitors at very high frequencies, along with constant advances in performance of power semiconductor devices, suggests a sizable shift in consumer power supplies market into this area in the near future. To operate dc-dc converter power...... method provides low complexity and low gate loss simultaneously. A direct design synthesis method is provided for resonant SEPIC converters employing this technique. Most experimental prototypes were developed using low cost, commercially available power semiconductors. Due to very fast transient...

  20. Parametric nanomechanical amplification at very high frequency.

    Science.gov (United States)

    Karabalin, R B; Feng, X L; Roukes, M L

    2009-09-01

    Parametric resonance and amplification are important in both fundamental physics and technological applications. Here we report very high frequency (VHF) parametric resonators and mechanical-domain amplifiers based on nanoelectromechanical systems (NEMS). Compound mechanical nanostructures patterned by multilayer, top-down nanofabrication are read out by a novel scheme that parametrically modulates longitudinal stress in doubly clamped beam NEMS resonators. Parametric pumping and signal amplification are demonstrated for VHF resonators up to approximately 130 MHz and provide useful enhancement of both resonance signal amplitude and quality factor. We find that Joule heating and reduced thermal conductance in these nanostructures ultimately impose an upper limit to device performance. We develop a theoretical model to account for both the parametric response and nonequilibrium thermal transport in these composite nanostructures. The results closely conform to our experimental observations, elucidate the frequency and threshold-voltage scaling in parametric VHF NEMS resonators and sensors, and establish the ultimate sensitivity limits of this approach.

  1. Fine frequency tuning of the PHOENIX charge breeder used as a probe for ECRIS plasmas

    International Nuclear Information System (INIS)

    Lamy, T.; Angot, J.; Melanie, M.J.; Medard, J.; Sortais, P.; Thuillier, T.; Galata, A.; Koivisto, Hannu; Tarvainen, Olli

    2012-01-01

    Fine frequency tuning of ECR ion sources is a main issue to optimize the production of multiply charged ion beams. The PHOENIX charge breeder operation has been tested in the range 13.75 - 14.5 GHz with an HF power of about 400 W. The effect of this tuning is analyzed by measuring the multi-ionization efficiency obtained for various characterized injected 1+ ion beams (produced by the 2.45 GHz COMIC source). The 1+/n+ method includes the capture and the multi ionization processes of the 1+ beam and may be considered as a plasma probe. The n+ spectra obtained could be considered, in first approach, as an image of the plasma of the charge breeder. However, in certain conditions it has been observed that the injection of a few hundreds of nA of 1+ ions (i.e.: Xe+) in the plasma of the charge breeder, is able to destroy the charge state distribution of the support gas (i.e.: up to 40 % of O 6+ and O 7+ disappears). The study of this phenomenon will be presented along with plasma potential measurements for various charge states. This study may help to understand the creation (or destruction) of highly charged ions inside an ECRIS. The paper is followed by the slides of the presentation. (authors)

  2. A high sensitivity momentum flux measuring instrument for plasma thruster exhausts and diffusive plasmas.

    Science.gov (United States)

    West, Michael D; Charles, Christine; Boswell, Rod W

    2009-05-01

    A high sensitivity momentum flux measuring instrument based on a compound pendulum has been developed for use with electric propulsion devices and radio frequency driven plasmas. A laser displacement system, which builds upon techniques used by the materials science community for surface stress measurements, is used to measure with high sensitivity the displacement of a target plate placed in a plasma thruster exhaust. The instrument has been installed inside a vacuum chamber and calibrated via two different methods and is able to measure forces in the range of 0.02-0.5 mN with a resolution of 15 microN. Measurements have been made of the force produced from the cold gas flow and with a discharge ignited using argon propellant. The plasma is generated using a Helicon Double Layer Thruster prototype. The instrument target is placed about 1 mean free path for ion-neutral charge exchange collisions downstream of the thruster exit. At this position, the plasma consists of a low density ion beam (10%) and a much larger downstream component (90%). The results are in good agreement with those determined from the plasma parameters measured with diagnostic probes. Measurements at various flow rates show that variations in ion beam velocity and plasma density and the resulting momentum flux can be measured with this instrument. The instrument target is a simple, low cost device, and since the laser displacement system used is located outside the vacuum chamber, the measurement technique is free from radio frequency interference and thermal effects. It could be used to measure the thrust in the exhaust of other electric propulsion devices and the momentum flux of ion beams formed by expanding plasmas or fusion experiments.

  3. Topics in high-intensity laser plasma interaction

    International Nuclear Information System (INIS)

    Leemans, W.P.

    1991-01-01

    The interaction of high intensity laser pulses with pre-formed and laser-produced plasmas is studied. Through experiments and simulations we have investigated stimulated Compton scattering in preformed plasmas and the plasma physics aspects of tunnel-ionized gases. A theoretical study is presented on the nonlinear dynamics of relativistic plasma waves driven by colinear optical mixing. The electron density-fluctuation spectra induced by stimulated Compton scattering have been directly observed for the first time. A CO2 laser was focused into pre-formed plasmas with densities n(e) varied from 0.4-6 x 10(exp 16) cu cm. The fluctuations corresponding to backscatter were probed using Thomson scattering. At low n(e), the scattered spectra peak at a frequency shift Delta omega is approximately kv e and appears to be in a linear regime. At the highest n(e), a nonlinear saturation of the SCS instability is observed due to a self-induced perturbation of the electron distribution function. Tunnel-ionized plasmas have been studied through experiments and particle simulations. Experimentally, qualitative evidence for plasma temperature control by varying the laser polarization was obtained by the measurement of stimulated Compton scattering fluctuation spectra and x-ray emission from such plasmas. A higher parallel temperature than expected from the single-particle tunneling model was observed. Simulations indicate that stochastic heating and the Weibel instability play an important role in plasma heating in all directions and isotropization. The non-linear dynamics associated with beatwave (Delta omega, Delta k) excited long wavelength plasma waves in the presence of strong, short wavelength density ripple have been examined, using the relativistic Lagrangian oscillator model. This model shows period doubling that roughly follows Feigenbaum scaling, and a transition to chaos

  4. High levels of circulating triiodothyronine induce plasma cell differentiation.

    Science.gov (United States)

    Bloise, Flavia Fonseca; Oliveira, Felipe Leite de; Nobrega, Alberto Félix; Vasconcellos, Rita; Cordeiro, Aline; Paiva, Luciana Souza de; Taub, Dennis D; Borojevic, Radovan; Pazos-Moura, Carmen Cabanelas; Mello-Coelho, Valéria de

    2014-03-01

    The effects of hyperthyroidism on B-cell physiology are still poorly known. In this study, we evaluated the influence of high-circulating levels of 3,5,3'-triiodothyronine (T3) on bone marrow, blood, and spleen B-cell subsets, more specifically on B-cell differentiation into plasma cells, in C57BL/6 mice receiving daily injections of T3 for 14 days. As analyzed by flow cytometry, T3-treated mice exhibited increased frequencies of pre-B and immature B-cells and decreased percentages of mature B-cells in the bone marrow, accompanied by an increased frequency of blood B-cells, splenic newly formed B-cells, and total CD19(+)B-cells. T3 administration also promoted an increase in the size and cellularity of the spleen as well as in the white pulp areas of the organ, as evidenced by histological analyses. In addition, a decreased frequency of splenic B220(+) cells correlating with an increased percentage of CD138(+) plasma cells was observed in the spleen and bone marrow of T3-treated mice. Using enzyme-linked immunospot assay, an increased number of splenic immunoglobulin-secreting B-cells from T3-treated mice was detected ex vivo. Similar results were observed in mice immunized with hen egg lysozyme and aluminum adjuvant alone or together with treatment with T3. In conclusion, we provide evidence that high-circulating levels of T3 stimulate plasma cytogenesis favoring an increase in plasma cells in the bone marrow, a long-lived plasma cell survival niche. These findings indicate that a stimulatory effect on plasma cell differentiation could occur in untreated patients with Graves' disease.

  5. Plasma inhomogeneities near the electrodes of a capacitively-coupled radio-frequency discharge containing dust particles

    International Nuclear Information System (INIS)

    Tawidian, H; Mikikian, M.; Couedel, L.; Lecas, T.

    2011-01-01

    Dusty plasmas can be found in fusion devices. In this paper we analyse a new phenomenon occurring during dust particle growth instabilities and consisting of the appearance of small plasma spheroids in the vicinity of discharge electrodes. Small plasma spheroids are evidenced and analyzed in front of the electrodes of a capacitively-coupled radio-frequency discharge in which dust particles are growing. These regions are characterized by a spherical shape, a slightly enhanced luminosity and are related to instabilities induced by the presence of dust particles. Several types of behaviors are identified and particularly their chaotic appearance or disappearance and their rotational motion along the electrode periphery. Correlations with the unstable behavior of the global plasma glow are performed. These analyses are obtained thanks to high-speed imaging which is the only diagnostics able to evidence these plasma spheroids

  6. Tha AGS Booster high frequency rf system

    International Nuclear Information System (INIS)

    Sanders, R.; Cameron, P.; Damn, R.

    1988-01-01

    A high level rf system, including a power amplifier and cavity has been designed for the AGS Booster. It covers a frequency range of 2.4 to 4.2 Mhz and will be used to accelerate high intensity proton, and low intensity polarized proton beams to 1.5 GeV and heavy ions to 0.35 GeV per nucleon. A total accelerating voltage of up to 90kV will be provided by two cavities, each having two gaps. The internally cross-coupled, pushpull cavities are driven by an adjacently located power amplifier. In order to accommodate the high beam intensity, up to 0.75 /times/ 10 13 protons per bunch, a low plate resistance power tetrode is used. The tube anode is magnetically coupled to one of the cavity's two paralleled cells. The amplifier is a grounded cathode configuration driven by a remotely located solid state amplifier

  7. Cultures of High-frequency Trading

    DEFF Research Database (Denmark)

    Lange, Ann-Christina; Lenglet, Marc; Seyfert, Robert

    2016-01-01

    As part of ongoing work to lay a foundation for social studies of high-frequency trading (HFT), this paper introduces the culture(s) of HFT as a sociological problem relating to knowledge and practice. HFT is often discussed as a purely technological development, where all that matters is the speed...... of allocating, processing and transmitting data. Indeed, the speed at which trades are executed and data transmitted is accelerating, and it is fair to say that algorithms are now the primary interacting agents operating in the financial markets. However, we contend that HFT is first and foremost a cultural...

  8. Pulsed-High Field/High-Frequency EPR Spectroscopy

    Science.gov (United States)

    Fuhs, Michael; Moebius, Klaus

    Pulsed high-field/high-frequency electron paramagnetic resonance (EPR) spectroscopy is used to disentangle many kinds of different effects often obscured in continuous wave (cw) EPR spectra at lower magnetic fields/microwave frequencies. While the high magnetic field increases the resolution of G tensors and of nuclear Larmor frequencies, the high frequencies allow for higher time resolution for molecular dynamics as well as for transient paramagnetic intermediates studied with time-resolved EPR. Pulsed EPR methods are used for example for relaxation-time studies, and pulsed Electron Nuclear DOuble Resonance (ENDOR) is used to resolve unresolved hyperfine structure hidden in inhomogeneous linewidths. In the present article we introduce the basic concepts and selected applications to structure and mobility studies on electron transfer systems, reaction centers of photosynthesis as well as biomimetic models. The article concludes with an introduction to stochastic EPR which makes use of an other concept for investigating resonance systems in order to increase the excitation bandwidth of pulsed EPR. The limited excitation bandwidth of pulses at high frequency is one of the main limitations which, so far, made Fourier transform methods hardly feasible.

  9. Internal modes in high-temperature plasmas

    International Nuclear Information System (INIS)

    Crew, G.B.

    1983-02-01

    The linear stability of current-carrying toroidal plamsas is examined to determine the possibility of exciting global internal modes. The ideal magnetohydrodynamic (MHD) theory provides a useful framework for the analysis of these modes, which involve a kinking of the central portion of the plasma column. Non-ideal effects can also be important, and these are treated for high-temperature regimes where the plasma is collisionless

  10. Simulation of plasma loading of high-pressure RF cavities

    Science.gov (United States)

    Yu, K.; Samulyak, R.; Yonehara, K.; Freemire, B.

    2018-01-01

    Muon beam-induced plasma loading of radio-frequency (RF) cavities filled with high pressure hydrogen gas with 1% dry air dopant has been studied via numerical simulations. The electromagnetic code SPACE, that resolves relevant atomic physics processes, including ionization by the muon beam, electron attachment to dopant molecules, and electron-ion and ion-ion recombination, has been used. Simulations studies have been performed in the range of parameters typical for practical muon cooling channels.

  11. Simulation of plasma loading of high-pressure RF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Yu, K. [Brookhaven National Lab. (BNL), Upton, NY (United States). Computational Science Initiative; Samulyak, R. [Brookhaven National Lab. (BNL), Upton, NY (United States). Computational Science Initiative; Stony Brook Univ., NY (United States). Dept. of Applied Mathematics and Statistics; Yonehara, K. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Freemire, B. [Northern Illinois Univ., DeKalb, IL (United States)

    2018-01-11

    Muon beam-induced plasma loading of radio-frequency (RF) cavities filled with high pressure hydrogen gas with 1% dry air dopant has been studied via numerical simulations. The electromagnetic code SPACE, that resolves relevant atomic physics processes, including ionization by the muon beam, electron attachment to dopant molecules, and electron-ion and ion-ion recombination, has been used. Simulations studies have also been performed in the range of parameters typical for practical muon cooling channels.

  12. Investigation of beech wood modified by radio-frequency discharge plasma

    Czech Academy of Sciences Publication Activity Database

    Novák, I.; Popelka, A.; Špitalský, Z.; Mičušík, M.; Omastová, M.; Valentin, M.; Sedliačik, J.; Janigová, I.; Kleinová, A.; Šlouf, Miroslav

    2015-01-01

    Roč. 119, September (2015), s. 88-94 ISSN 0042-207X Institutional support: RVO:61389013 Keywords : radio-frequency plasma * beech wood * adhesive properties Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.558, year: 2015

  13. High speed and high functional inverter power supplies for plasma generation and control, and their performance

    International Nuclear Information System (INIS)

    Uesugi, Yoshihiko; Razzak, Mohammad A.; Kondo, Kenji; Kikuchi, Yusuke; Takamura, Shuichi; Imai, Takahiro; Toyoda, Mitsuhiro

    2003-01-01

    The Rapid development of high power and high speed semiconductor switching devices has led to their various applications in related plasma fields. Especially, a high speed inverter power supply can be used as an RF power source instead of conventional linear amplifiers and a power supply to control the magnetic field in a fusion plasma device. In this paper, RF thermal plasma production and plasma heating experiments are described emphasis placed on using a static induction transistor inverter at a frequency range between 200 kHz and 2.5 MHz as an RF power supply. Efficient thermal plasma production is achieved experimentally by using a flexible and easily operated high power semiconductor inverter power supply. Insulated gate bipolar transistor (IGBT) inverter power supplies driven by a high speed digital signal processor are applied as tokamak joule coil and vertical coil power supplies to control plasma current waveform and plasma equilibrium. Output characteristics, such as the arbitrary bipolar waveform generation of a pulse width modulation (PWM) inverter using digital signal processor (DSP) can be successfully applied to tokamak power supplies for flexible plasma current operation and fast position control of a small tokamak. (author)

  14. Low-frequency instabilities of electron-hole plasmas in crossed fields

    International Nuclear Information System (INIS)

    Schneider, W.; Kirchesch, P.

    1978-01-01

    Using local point-contact probes, we observed two types of low-frequency instabilities in n-InSb at 85 K if the samples were exposed to crossed fields. One is a local density instability with threshold frequencies of f = 1 ... 20 Mc, the other a more turbulent current instability. The threshold values of U 0 and B for the onset of these instabilities and the dependence of their amplitudes on the fields have been measured. If a rectangular semiconductor slab is placed in crossed fields, regions of high electric field strength at opposite edges of the contacts are caused by the distortion of the Hall field, giving rise to the generation of electron-hole plasmas by impact ionization. These plasmas are the sources of the observed instabilities. This is especially evident in the case of the local density instability, which originates at the anode high field corner. Several possible reasons for the development of the instabilities are discussed. (orig.) [de

  15. Oblique propagation of electron thermal modes below the electron plasma frequency without boundary effects

    International Nuclear Information System (INIS)

    Ohnuma, T.; Watanabe, T.; Sanuki, H.

    1981-08-01

    Propagation characteristics and refractive effects of an oblique electron thermal mode without boundary effects below the electron plasma frequency are studied experimentally and theoretically in an inhomogeneous magnetized plasma. The behavior of this mode observed experimentally was confirmed by the theoretical analysis based on a new type of ray theory. (author)

  16. Low-frequency dust-lower-hybrid modes in a dusty plasma

    International Nuclear Information System (INIS)

    Salimullah, M.

    1995-10-01

    The existence of low-frequency dust-lower-hybrid modes in a magnetized dusty plasma has been examined. These modes arise on account of the inequalities of charge and number densities of electrons, ions, and dust particles, and finite Larmor radius effects in a dusty plasma. (author). 14 refs

  17. Construction of a high beta plasma source

    International Nuclear Information System (INIS)

    Naraghi, M.; Torabi-Fard, A.

    1976-02-01

    A high beta plasma source has been designed and constructed. This source will serve as a means of developing and exercising different diagnostic techniques as required for ALVAND I, linear theta pinch experiment. Also, it will serve to acquaint the technicians with some of the techniques and safety rules of high voltage and capacitor discharge experiments. The operating parameters of the theta pinch and Z-pinch preionization is presented and the program of diagnostic measurements on the high beta plasma source is discussed

  18. High Tc superconductors at microwave frequencies

    International Nuclear Information System (INIS)

    Gruener, G.

    1991-01-01

    The author discusses various experiments conducted in the micro- and millimeter wave spectral range on thin film and single crystal specimens of the high temperature oxide superconductors. For high quality film the surface resistance R s is, except at low temperatures, due to thermally excited carriers, with extrinsic effects playing only a secondary role. Because of the low loss various passive microwave components, such as resonators, delay lines and filters, with performance far superior to those made of normal metals can be fabricated. The conductivity measured at millimeter wave frequencies displays a peak below T c . Whether this is due to coherence factors or due to the change of the relaxation rate when the materials enter the superconducting state remains to be seen

  19. High-frequency Stark effect and two-quantum transitions

    International Nuclear Information System (INIS)

    Hildebrandt, J

    2007-01-01

    A problem which motivated a great deal of work about 20 years ago, namely, satellite lines occurring for atomic emitters undergoing a harmonic perturbation, is revisited. On a theoretical point of view, two photon mechanisms or equivalent are involved to explain those satellites due to high-frequency electric fields. Although today the activity on these problems is rather low, interest in observing such effects in the domain of x-ray spectroscopy exists, namely for hot and dense plasmas. More generally, satellites can be also seen as connected to turbulence diagnostics. This mainly motivates the design of plasmas and improvements of x-ray spectroscopy techniques. However, up to now, attempts to extend the methods of nonlinear spectroscopy to this domain have been rather disappointing. As a promotion for a resurgence of the field, an improved theory, founded on formalisms of nonlinear optics, is developed to suggest a new interpretation of the experiments. Previous publications are modified and an old problem is closed. Hopefully, this will help us to stimulate new applications of two-photon techniques in plasmas

  20. High-frequency behavior of magnetic composites

    International Nuclear Information System (INIS)

    Lagarkov, Andrey N.; Rozanov, Konstantin N.

    2009-01-01

    The paper reviews recent progress in the field of microwave magnetic properties of composites. The problem under discussion is developing composites with high microwave permeability that are needed in many applications. The theory of magnetic composites is briefly sketched with the attention paid to the laws governing the magnetic frequency dispersion in magnetic materials and basic mixing rules for composites. Recent experimental reports on the microwave performance of magnetic composites, as well as data on the agreement of the mixing rules with the measured permeability of composites that are available from the literature are discussed. From the data, a conclusion is made that the validity of a mixing rule is determined by the permeability contrast in the composite, i.e., the difference between permeability of inclusions and that of the host matrix. When the contrast is low, the Maxwell Garnet mixing rule is frequently valid. When the contrast is high, which is of the most interest for obtaining high microwave permeability of a composite, no conventionally accepted theory is capable of accurately predicting the permeability of the composites. Therefore, the mixing rules do not allow the microwave properties of magnetic composites to be predicted when the permeability of inclusions is high, that is the case of the most interest. Because of that, general limitations to the microwave performance of composites are of importance. In particular, an important relation constraining the microwave permeability of composites follows from Kittel's theory of ferromagnetic resonance and analytical properties of frequency dependence of permeability. Another constraint concerning the bandwidth of electromagnetic wave absorbers follows from the Kramers-Kronig relations for the reflection coefficient. The constraints are of importance in design and analysis of electromagnetic wave absorbers and other devices that employ the microwave magnetic properties of composites, such as

  1. Frequency downshifting and trapping of an electromagnetic wave by a rapidly created spatially periodic plasma

    International Nuclear Information System (INIS)

    Faith, J.; Kuo, S.P.; Huang, J.

    1997-01-01

    Experimental and numerical results of the interaction of electromagnetic waves with rapidly time varying spatially periodic plasmas are presented. It is shown that a number of Floquet modes, each with their own oscillation frequency, are created during the interaction. Included among these modes are downshifted waves which will not exist in the single slab case, and also waves with a larger upshifted frequency than one can obtain with a single plasma layer of the same density. In addition, the periodic structure is characterized by pass and stop bands that are different from those of a single plasma layer, and the frequencies of the downshifted modes falling in the stop band of a single plasma layer. Therefore these waves are trapped within the plasma structure until the plasma decays away. To show this phenomenon a chamber experiment is conducted, with the periodic plasma being produced by a capacitive discharge. The power spectrum recorded for waves interacting with the plasma shows vastly improved efficiency in the downshift mechanism, which the numerical calculations suggest is related to the trapping of the wave within the plasma. Reproducible results are recorded which are found to agree well with the numerical simulation. copyright 1997 The American Physical Society

  2. Experimental study of high beta toroidal plasmas

    International Nuclear Information System (INIS)

    Kellman, A.G.

    1983-09-01

    Experiments on the Wisconsin Levitated Toroidal Octupole have produced a wide range of stable high β plasmas with β significantly above single fluid MHD theory predictions. A stable β approx. 8% plasma, twice the fluid limit, is obtained with 5 rho/sub i/ approx. L/sub n/ and tau/sub β/ approx. = 6000 tau/sub Alfven/ = 600 μsec. The enhanced stability is explained with a kinetic treatment that includes the effect of finite ion gyroradius which couples the ballooning mode to an ion drift wave. In a more collisional, large gyroradius (2 rho/sub i/ approx. L/sub n/) regime, a stable β approx. 35% plasma is obtained with a decay time of 1000 Alfven times. Measurement of the equilibrium magnetic field in this regime indicates that the diamagnetic current density is five times smaller than predicted by ideal MHD, probably due to ion gyroviscosity. Particle transport is anomalous and ranges from agreement with the classical diffusion rate at the highest beta, lowest field plasma (B/sub P/ = 200 G), to thirteen times the classical rate in a β=11%, high field plasma (B/sub P/ = 860 G) where the level of enhancement increase with magnetic field. Fluctuations in density, electrostatic potential, and magnetic field have been studied in plasmas with β from 0.1% to 40%

  3. Characterizing electrostatic turbulence in tokamak plasmas with high MHD activity

    Energy Technology Data Exchange (ETDEWEB)

    Guimaraes-Filho, Z O; Santos Lima, G Z dos; Caldas, I L; Nascimento, I C; Kuznetsov, Yu K [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66316, 05315-970, Sao Paulo, SP (Brazil); Viana, R L, E-mail: viana@fisica.ufpr.b [Departamento de Fisica, Universidade Federal do Parana, Caixa Postal 19044, 81531-990, Curitiba, PR (Brazil)

    2010-09-01

    One of the challenges in obtaining long lasting magnetic confinement of fusion plasmas in tokamaks is to control electrostatic turbulence near the vessel wall. A necessary step towards achieving this goal is to characterize the turbulence level and so as to quantify its effect on the transport of energy and particles of the plasma. In this paper we present experimental results on the characterization of electrostatic turbulence in Tokamak Chauffage Alfven Bresilien (TCABR), operating in the Institute of Physics of University of Sao Paulo, Brazil. In particular, we investigate the effect of certain magnetic field fluctuations, due to magnetohydrodynamical (MHD) instabilities activity, on the spectral properties of electrostatic turbulence at plasma edge. In some TCABR discharges we observe that this MHD activity may increase spontaneously, following changes in the edge safety factor, or after changes in the radial electric field achieved by electrode biasing. During the high MHD activity, the magnetic oscillations and the plasma edge electrostatic turbulence present several common linear spectral features with a noticeable dominant peak in the same frequency. In this article, dynamical analyses were applied to find other alterations on turbulence characteristics due to the MHD activity and turbulence enhancement. A recurrence quantification analysis shows that the turbulence determinism radial profile is substantially changed, becoming more radially uniform, during the high MHD activity. Moreover, the bicoherence spectra of these two kinds of fluctuations are similar and present high bicoherence levels associated with the MHD frequency. In contrast with the bicoherence spectral changes, that are radially localized at the plasma edge, the turbulence recurrence is broadly altered at the plasma edge and the scrape-off layer.

  4. A high frequency, high power CARM proposal for the DEMO ECRH system

    International Nuclear Information System (INIS)

    Mirizzi, Francesco; Spassovsky, Ivan; Ceccuzzi, Silvio; Dattoli, Giuseppe; Di Palma, Emanuele; Doria, Andrea; Gallerano, Gianpiero; Lampasi, Alessandro; Maffia, Giuseppe; Ravera, GianLuca; Sabia, Elio; Tuccillo, Angelo Antonio; Zito, Pietro

    2015-01-01

    Highlights: • ECRH system for DEMO. • Cyclotron Auto-Resonance Maser (CARM) devices. • Relativistic electron beams. • Bragg reflectors. • High voltage pulse modulators. - Abstract: ECRH&CD systems are extensively used on tokamak plasmas due to their capability of highly tailored power deposition, allowing very localised heating and non-inductive current drive, useful for MHD and profiles control. The high electron temperatures expected in DEMO will require ECRH systems with operating frequency in the 200–300 GHz range, equipped with a reasonable number of high power (P ≥ 1 MW) CW RF sources, for allowing central RF power deposition. In this frame the ENEA Fusion Department (Frascati) is coordinating a task force aimed at the study and realisation of a suitable high power, high frequency reliable source.

  5. A high frequency, high power CARM proposal for the DEMO ECRH system

    Energy Technology Data Exchange (ETDEWEB)

    Mirizzi, Francesco, E-mail: francesco.mirizzi@enea.it [Consorzio CREATE, Via Claudio 21, I-80125 Napoli (Italy); Spassovsky, Ivan [Unità Tecnica Applicazioni delle Radiazioni – ENEA, C.R. Frascati, via E. Fermi 45, I-00044 Frascati (Italy); Ceccuzzi, Silvio [Unità Tecnica Fusione – ENEA C. R. Frascati, via E. Fermi 45, 00044 Frascati, Roma (Italy); Dattoli, Giuseppe; Di Palma, Emanuele; Doria, Andrea; Gallerano, Gianpiero [Unità Tecnica Applicazioni delle Radiazioni – ENEA, C.R. Frascati, via E. Fermi 45, I-00044 Frascati (Italy); Lampasi, Alessandro; Maffia, Giuseppe; Ravera, GianLuca [Unità Tecnica Fusione – ENEA C. R. Frascati, via E. Fermi 45, 00044 Frascati, Roma (Italy); Sabia, Elio [Unità Tecnica Applicazioni delle Radiazioni – ENEA, C.R. Frascati, via E. Fermi 45, I-00044 Frascati (Italy); Tuccillo, Angelo Antonio; Zito, Pietro [Unità Tecnica Fusione – ENEA C. R. Frascati, via E. Fermi 45, 00044 Frascati, Roma (Italy)

    2015-10-15

    Highlights: • ECRH system for DEMO. • Cyclotron Auto-Resonance Maser (CARM) devices. • Relativistic electron beams. • Bragg reflectors. • High voltage pulse modulators. - Abstract: ECRH&CD systems are extensively used on tokamak plasmas due to their capability of highly tailored power deposition, allowing very localised heating and non-inductive current drive, useful for MHD and profiles control. The high electron temperatures expected in DEMO will require ECRH systems with operating frequency in the 200–300 GHz range, equipped with a reasonable number of high power (P ≥ 1 MW) CW RF sources, for allowing central RF power deposition. In this frame the ENEA Fusion Department (Frascati) is coordinating a task force aimed at the study and realisation of a suitable high power, high frequency reliable source.

  6. Wall stabilization of high beta plasmas in DIII-D

    International Nuclear Information System (INIS)

    Taylor, T.S.; Strait, E.J.; Lao, L.L.; Turnbull, A.D.; Burrell, K.H.; Chu, M.S.; Ferron, J.R.; Groebner, R.J.; La Haye, R.J.; Mauel, M.

    1995-02-01

    Detailed analysis of recent high beta discharges in the DIII-D tokamak demonstrates that the resistive vacuum vessel can provide stabilization of low n magnetohydrodynamic (MHD) modes. The experimental beta values reaching up to β T = 12.6% are more than 30% larger than the maximum stable beta calculated with no wall stabilization. Plasma rotation is essential for stabilization. When the plasma rotation slows sufficiently, unstable modes with the characteristics of the predicted open-quotes resistive wallclose quotes mode are observed. Through slowing of the plasma rotation between the q = 2 and q = 3 surfaces with the application of a non-axisymmetric field, the authors have determined that the rotation at the outer rational surfaces is most important, and that the critical rotation frequency is of the order of Ω/2π = 1 kHz

  7. Angular dependence of high Mach number plasma interactions

    International Nuclear Information System (INIS)

    Thomas, V.A.; Brecht, S.H.

    1987-01-01

    In this paper a 2-1/2-dimensional hybrid code is used to examine the collisionless large spatial scale (kc/ω pi ∼ 1) low-frequency (ω ∼ ω ci ) interaction initiated by a plasma shell of finite width traveling at high Alfven Mach number relative to a uniform background plasma. Particular attention is given to the angle of the relative velocity relative to the ambient magnetic field for the range of angles O < θ < π/2. An attempt is made to parameterize some of the important physics including the Alfven ion cyclotron instability, the field-aligned electromagnetic ion counter streaming instability, mixing of the plasma shell with the background ions, and structuring of the interaction region. These results are applicable to various astrophysical interactions such as bow shocks and interplanetary shocks

  8. Effect of Radio-Frequency and Low-Frequency Bias Voltage on the Formation of Amorphous Carbon Films Deposited by Plasma Enhanced Chemical Vapor Deposition

    International Nuclear Information System (INIS)

    Manis-Levy, Hadar; Mintz, Moshe H.; Livneh, Tsachi; Zukerman Ido; Raveh, Avi

    2014-01-01

    The effect of radio-frequency (RF) or low-frequency (LF) bias voltage on the formation of amorphous hydrogenated carbon (a-C:H) films was studied on silicon substrates with a low methane (CH 4 ) concentration (2–10 vol.%) in CH 4 +Ar mixtures. The bias substrate was applied either by RF (13.56 MHz) or by LF (150 kHz) power supply. The highest hardness values (∼18–22 GPa) with lower hydrogen content in the films (∼20 at.%) deposited at 10 vol.% CH 4 , was achieved by using the RF bias. However, the films deposited using the LF bias, under similar RF plasma generation power and CH 4 concentration (50 W and 10 vol.%, respectively), displayed lower hardness (∼6–12 GPa) with high hydrogen content (∼40 at.%). The structures analyzed by Fourier Transform Infrared (FTIR) and Raman scattering measurements provide an indication of trans-polyacetylene structure formation. However, its excessive formation in the films deposited by the LF bias method is consistent with its higher bonded hydrogen concentration and low level of hardness, as compared to the film prepared by the RF bias method. It was found that the effect of RF bias on the film structure and properties is stronger than the effect of the low-frequency (LF) bias under identical radio-frequency (RF) powered electrode and identical PECVD (plasma enhanced chemical vapor deposition) system configuration. (plasma technology)

  9. Quantum Phenomena in High Energy Density Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Murnane, Margaret [Univ. of Colorado, Boulder, CO (United States); Kapteyn, Henry [Univ. of Colorado, Boulder, CO (United States)

    2017-05-10

    The possibility of implementing efficient (phase matched) HHG upconversion of deep- UV lasers in multiply-ionized plasmas, with potentially unprecedented conversion efficiency is a fascinating prospect. HHG results from the extreme nonlinear response of matter to intense laser light:high harmonics are radiated as a result of a quantum coherent electron recollision process that occurs during laser field ionization of an atom. Under current support from this grant in work published in Science in 2015, we discovered a new regime of bright HHG in highly-ionized plasmas driven by intense UV lasers, that generates bright harmonics to photon energies >280eV

  10. Large Amplitude Low Frequency Waves in a Magnetized Nonuniform Electron-Positron-Ion Plasma

    Institute of Scientific and Technical Information of China (English)

    Q. Haque; H. Saleem

    2004-01-01

    @@ It is shown that the large amplitude low-frequency electromagnetic drift waves in electron-positron-ion plasmas might give rise to dipolar vortices. A linear dispersion relation of several coupled electrostatic and electromagnetic low-frequency modes is obtained. The relevance of this work to both laboratory and astrophysical situations is pointed out.

  11. Nonlinear beat excitation of low frequency wave in degenerate plasmas

    Science.gov (United States)

    Mir, Zahid; Shahid, M.; Jamil, M.; Rasheed, A.; Shahbaz, A.

    2018-03-01

    The beat phenomenon due to the coupling of two signals at slightly different frequencies that generates the low frequency signal is studied. The linear dispersive properties of the pump and sideband are analyzed. The modified nonlinear dispersion relation through the field coupling of linear modes against the beat frequency is derived in the homogeneous quantum dusty magnetoplasmas. The dispersion relation is used to derive the modified growth rate of three wave parametric instability. Moreover, significant quantum effects of electrons through the exchange-correlation potential, the Bohm potential, and the Fermi pressure evolved in macroscopic three wave interaction are presented. The analytical results are interpreted graphically describing the significance of the work. The applications of this study are pointed out at the end of introduction.

  12. Propagation characteristics of a Gaussian laser beam in plasma with modulated collision frequency

    International Nuclear Information System (INIS)

    Wang Ying; Yuan Chengxun; Zhou Zhongxiang; Gao Ruilin; Li Lei; Du Yanwei

    2012-01-01

    The propagation characteristics of a Gaussian laser beam in cold plasma with the electron collision frequency modulated by laser intensity are presented. The nonlinear dynamics of the ponderomotive force, which induce nonlinear self-focusing as opposed to spatial diffraction, are considered. The effective dielectric function of the Drude model and complex eikonal function are adopted in deriving coupled differential equations of the varying laser beam parameters. In the framework of ponderomotive nonlinearity, the frequency of electron collision in plasmas, which is proportional to the spatial electron density, is strongly interrelated with the laser beam propagation characteristics. Hence, the propagation properties of the laser beam and the modulated electron collision frequency distribution in plasma were studied and explained in depth. Employing this self-consistent method, the obtained simulation results approach practical conditions, which is of significance to the study of laser–plasma interactions.

  13. Initial frequency shift of large amplitude plasma wave, 2

    International Nuclear Information System (INIS)

    Yamanaka, K.; Sugihara, R.; Ohsawa, Y.; Kamimura, T.

    1979-07-01

    A nonlinear complex frequency shift of the ion acoustic wave in the initial phase defined by 0 0 and ωsub(s)/k as long as ωsub(s) >> γsub( l), where phi 0 , ωsub(s), γsub( l) and t sub(c) are the initial value of the potential, the frequency of the wave, the linear Landau damping coefficient and the time for the first minimum of the amplitude oscillation, respectively. A simulation study is also carried out. The results confirm the validity of the theory. (author)

  14. Numerical simulation of dual frequency etching reactors: Influence of the external process parameters on the plasma characteristics

    International Nuclear Information System (INIS)

    Georgieva, V.; Bogaerts, A.

    2005-01-01

    A one-dimensional particle-in-cell/Monte Carlo model is used to investigate Ar/CF 4 /N 2 discharges sustained in capacitively coupled dual frequency reactors, with special emphasis on the influence of the reactor parameters such as applied voltage amplitudes and frequencies of the two voltage sources. The presented calculation results include plasma density, ion current, average sheath potential and width, electron and ion average energies and energy distributions, and ionization rates. The simulations were carried out for high frequencies (HFs) of 27, 40, 60, and 100 MHz and a low frequency (LF) of 1 or 2 MHz, varying the LF voltage and keeping the HF voltage constant and vice versa. It is observed that the decoupling of the two sources is possible by increasing the applied HF to very high values (above 60 MHz) and it is not defined by the frequency ratio. Both voltage sources have influence on the plasma characteristics at a HF of 27 MHz and to some extent at 40 MHz. At HFs of 60 and 100 MHz, the plasma density and ion flux are determined only by the HF voltage source. The ion energy increases and the ion energy distribution function (IEDF) becomes broader with HF or LF voltage amplitude, when the other voltage is kept constant. The IEDF is broader with the increase of HF or the decrease of LF

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

    Science.gov (United States)

    Doleans, Marc

    2016-12-01

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

  16. 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.

  17. Ion source plasma parameters measurement based on Langmuir probe with commercial frequency sweep

    International Nuclear Information System (INIS)

    Xie, Y.H.; Hu, C.D.; Liu, S.; Shong, S.H.; Jiang, C.C.; Liu, Z.M.

    2010-01-01

    Langmuir probe is one of the main diagnostic tools to measure the plasma parameters in the ion source. In this article, the commercial frequency power, which is sine wave of 50 Hz, was supplied on the Langmuir probe to measure the plasma parameters. The best feature of this probe sweep voltage is that it does not need extra design. The probe I-V characteristic curve can be got in less than 5 ms and the plasma parameters, the electron temperature and the electron density, varying with the time can be got in one plasma discharge of 400 ms.

  18. Operation of the ORNL High Particle Flux Helicon Plasma Source

    International Nuclear Information System (INIS)

    Goulding, Richard Howell; Biewer, Theodore M.; Caughman, John B.; Chen, Guangye; Owen, Larry W.; Sparks, Dennis O.

    2011-01-01

    A high power, high particle flux rf-based helicon plasma source has been constructed at ORNL and operated at power levels up to 30 kW. High-density hydrogen and helium plasmas have been produced. The source has been designed as the basis for a linear plasma materials interaction (PMI) test facility that will generate particle fluxes Gamma(p) > 10(23) M-3 s(-1), and utilize additional ion and electron cyclotron heating to produce high parallel (to the magnetic field) heat fluxes of similar to 10 MW/m(2). An rf-based source for PMI research is of interest because high plasma densities are generated with no internal electrodes, allowing true steady state operation with minimal impurity generation. The ORNL helicon source has a diameter of 15 cm and to-date has operated at a frequency f = 13.56 MHz, with magnetic field strength vertical bar B vertical bar in the antenna region up to similar to 0.15 T. Maximum densities of 3 x 10(19) M-3 in He and 2.5 x 10(19) m(-3) in H have been achieved. Radial density profiles have been seen to be dependent on the axial vertical bar B vertical bar profile.

  19. Operation of the ORNL High Particle Flux Helicon Plasma Source

    International Nuclear Information System (INIS)

    Goulding, R. H.; Biewer, T. M.; Caughman, J. B. O.; Chen, G. C.; Owen, L. W.; Sparks, D. O.

    2011-01-01

    A high power, high particle flux rf-based helicon plasma source has been constructed at ORNL and operated at power levels up to 30 kW. High-density hydrogen and helium plasmas have been produced. The source has been designed as the basis for a linear plasma materials interaction (PMI) test facility that will generate particle fluxes Γ p 10 23 m -3 s -1 , and utilize additional ion and electron cyclotron heating to produce high parallel (to the magnetic field) heat fluxes of ∼10 MW/m 2 . An rf-based source for PMI research is of interest because high plasma densities are generated with no internal electrodes, allowing true steady state operation with minimal impurity generation. The ORNL helicon source has a diameter of 15 cm and to-date has operated at a frequency f = 13.56 MHz, with magnetic field strength |B| in the antenna region up to ∼0.15 T. Maximum densities of 3x10 19 m -3 in He and 2.5x10 19 m -3 in H have been achieved. Radial density profiles have been seen to be dependent on the axial |B| profile.

  20. Plasma phospholipid pentadecanoic acid, EPA, and DHA, and the frequency of dairy and fish product intake in young children.

    Science.gov (United States)

    Lund-Blix, Nicolai A; Rønningen, Kjersti S; Bøås, Håkon; Tapia, German; Andersen, Lene F

    2016-01-01

    There is a lack of studies comparing dietary assessment methods with the biomarkers of fatty acids in children. The objective was to evaluate the suitability of a food frequency questionnaire (FFQ) to rank young children according to their intake of dairy and fish products by comparing food frequency estimates to the plasma phospholipid fatty acids pentadecanoic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Cross-sectional data for the present study were derived from the prospective cohort 'Environmental Triggers of Type 1 Diabetes Study'. Infants were recruited from the Norwegian general population during 2001-2007. One hundred and ten (age 3-10 years) children had sufficient volumes of plasma and FFQ filled in within 2 months from blood sampling and were included in this evaluation study. The quantitative determination of plasma phospholipid fatty acids was done by fatty acid methyl ester analysis. The association between the frequency of dairy and fish product intake and the plasma phospholipid fatty acids was assessed by a Spearman correlation analysis and by investigating whether participants were classified into the same quartiles of distribution. Significant correlations were found between pentadecanoic acid and the intake frequency of total dairy products (r=0.29), total fat dairy products (r=0.39), and cheese products (r=0.36). EPA and DHA were significantly correlated with the intake frequency of oily fish (r=0.26 and 0.37, respectively) and cod liver/fish oil supplements (r=0.47 for EPA and r=0.50 DHA). To a large extent, the FFQ was able to classify individuals into the same quartile as the relevant fatty acid biomarker. The present study suggests that, when using the plasma phospholipid fatty acids pentadecanoic acid, EPA, and DHA as biomarkers, the FFQ used in young children showed a moderate capability to rank the intake frequency of dairy products with a high-fat content and cod liver/fish oil supplements.

  1. Effect of high-frequency excitation on natural frequencies of spinning discs

    DEFF Research Database (Denmark)

    Hansen, Morten Hartvig

    2000-01-01

    The effect of high-frequency, non-resonant parametric excitation on the low-frequency response of spinning discs is considered. The parametric excitation is obtained through a non-constant rotation speed, where the frequency of the pulsating overlay is much higher than the lowest natural frequenc......The effect of high-frequency, non-resonant parametric excitation on the low-frequency response of spinning discs is considered. The parametric excitation is obtained through a non-constant rotation speed, where the frequency of the pulsating overlay is much higher than the lowest natural...

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

    Energy Technology Data Exchange (ETDEWEB)

    Moiseenko, V. E., E-mail: moiseenk@ipp.kharkov.ua; Stadnik, Yu. S., E-mail: stadnikys@kipt.kharkov.ua [National Academy of Sciences of Ukraine, National Science Center Kharkov Institute of Physics and Technology (Ukraine); Lysoivan, A. I., E-mail: a.lyssoivan@fz-juelich.de [Royal Military Academy, EURATOM-Belgian State Association, Laboratory for Plasma Physics (Belgium); Korovin, V. B. [National Academy of Sciences of Ukraine, National Science Center Kharkov Institute of Physics and Technology (Ukraine)

    2013-11-15

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

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  4. High-order harmonics generation from overdense plasmas

    International Nuclear Information System (INIS)

    Quere, F.; Thaury, C.; Monot, P.; Martin, Ph.; Geindre, J.P.; Audebert, P.; Marjoribanks, R.

    2006-01-01

    Complete test of publication follows. When an intense laser beam reflects on an overdense plasma generated on a solid target, high-order harmonics of the incident laser frequency are observed in the reflected beam. This process provides a way to produce XUV femtosecond and attosecond pulses in the μJ range from ultrafast ultraintense lasers. Studying the mechanisms responsible for this harmonic emission is also of strong fundamental interest: just as HHG in gases has been instrumental in providing a comprehensive understanding of basic intense laser-atom interactions, HHG from solid-density plasmas is likely to become a unique tool to investigate many key features of laser-plasma interactions at high intensities. We will present both experimental and theoretical evidence that two mechanisms contribute to this harmonic emission: - Coherent Wake Emission: in this process, harmonics are emitted by plasma oscillations in te overdense plasma, triggered in the wake of jets of Brunel electrons generated by the laser field. - The relativistic oscillating mirror: in this process, the intense laser field drives a relativistic oscillation of the plasma surface, which in turn gives rise to a periodic phase modulation of the reflected beam, and hence to the generation of harmonics of the incident frequency. Left graph: experimental harmonic spectrum from a polypropylene target, obtained with 60 fs laser pulses at 10 19 W/cm 2 , with a very high temporal contrast (10 10 ). The plasma frequency of this target corresponds to harmonics 15-16, thus excluding the CWE mechanism for the generation of harmonics of higher orders. Images on the right: harmonic spectra from orders 13 et 18, for different distances z between the target and the best focus. At the highest intensity (z=0), harmonics emitted by the ROM mechanism are observed above the 15th order. These harmonics have a much smaller spectral width then those due to CWE (below the 15th order). These ROM harmonics vanish as soon

  5. Development and experimental evaluation of theoretical models for ion cyclotron resonance frequency heating of tokamak plasmas

    International Nuclear Information System (INIS)

    Mantsinen, M.

    1999-01-01

    Heating with electromagnetic waves in the ion cyclotron range of frequencies (ICRF) is a well-established method for auxiliary heating of present-day tokamak plasmas and is envisaged as one of the main heating techniques for the International Thermonuclear Experimental Reactor (ITER) and future reactor plasmas. In order to predict the performance of ICRF heating in future machines, it is important to benchmark present theoretical modelling with experimental results on present tokamaks. This thesis reports on development and experimental evaluation of theoretical models for ICRF heating at the Joint European Torus (JET). Several ICRF physics effects and scenarios have been studied. Direct importance to the ITER is the theoretical analysis of ICRF heating experiments with deuterium-tritium (D-T) plasmas. These experiments clearly demonstrate the potential of ICRF heating for auxiliary heating of reactor plasmas. In particular, scenarios with potential for good bulk ion heating and enhanced D-T fusion reactivity have been identified. Good bulk ion heating is essential for reactor plasmas in order to obtain a high ion temperature and a high fusion reactivity. In JET good bulk ion heating with ICRF waves has been achieved in high-performance discharges by adding ICRF heating to neutral beam injection. In these experiments, as in other JET discharges where damping at higher harmonics of the ion cyclotron frequency takes place, so-called finite Larmor radius (FLR) effects play an important role. Due to FLR effects, the resonating ion velocity distribution function can have a strong influence on the power deposition. Evidence for this effect has been obtained from the third harmonic deuterium heating experiments. Because of FLR effects, the wave-particle interaction can also become weak at certain ion energies, which prevents resonating ions from reaching higher energies. When interacting with the wave, an ion receives not only a change in energy but also a change in

  6. Development and experimental evaluation of theoretical models for ion cyclotron resonance frequency heating of tokamak plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Mantsinen, M. [Helsinki Univ. of Technology, Espoo (Finland). Dept. of Technical Physics

    1999-06-01

    Heating with electromagnetic waves in the ion cyclotron range of frequencies (ICRF) is a well-established method for auxiliary heating of present-day tokamak plasmas and is envisaged as one of the main heating techniques for the International Thermonuclear Experimental Reactor (ITER) and future reactor plasmas. In order to predict the performance of ICRF heating in future machines, it is important to benchmark present theoretical modelling with experimental results on present tokamaks. This thesis reports on development and experimental evaluation of theoretical models for ICRF heating at the Joint European Torus (JET). Several ICRF physics effects and scenarios have been studied. Direct importance to the ITER is the theoretical analysis of ICRF heating experiments with deuterium-tritium (D-T) plasmas. These experiments clearly demonstrate the potential of ICRF heating for auxiliary heating of reactor plasmas. In particular, scenarios with potential for good bulk ion heating and enhanced D-T fusion reactivity have been identified. Good bulk ion heating is essential for reactor plasmas in order to obtain a high ion temperature and a high fusion reactivity. In JET good bulk ion heating with ICRF waves has been achieved in high-performance discharges by adding ICRF heating to neutral beam injection. In these experiments, as in other JET discharges where damping at higher harmonics of the ion cyclotron frequency takes place, so-called finite Larmor radius (FLR) effects play an important role. Due to FLR effects, the resonating ion velocity distribution function can have a strong influence on the power deposition. Evidence for this effect has been obtained from the third harmonic deuterium heating experiments. Because of FLR effects, the wave-particle interaction can also become weak at certain ion energies, which prevents resonating ions from reaching higher energies. When interacting with the wave, an ion receives not only a change in energy but also a change in

  7. High-Latitude Space Plasma Physics

    International Nuclear Information System (INIS)

    Hultqvist, B.; Hagfors, T.

    1983-01-01

    This book constitutes the proceedings of the Nobel Symposium No. 54 on High Latitude Magnetospheric/Ionospheric Plasma Physics. The main purpose of the symposium was to prepare for the European research effort in space plasma physics in the mid-1980's, in which two major constituents are the European Incoherent Scatter Association (EISCAT) facilities and the Swedish satellite Viking. The physics of the high-latitude ionosphere and how this part of near space is affected by the properties of the solar wind and the interplanetary magnetic field are explored. A detailed discussion is provided on high-latitude magnetospheric physics at altitudes of 1-2 earth radii, the main focus of the Viking project. Specific topics considered include the role of the auroral ionosphere in magnetospheric substorms, the low altitude cleft, ionospheric modification and stimulated emissions, plasma physics on auroral field lines, solar wind-magnetosphere energy coupling, cold plasma distribution above a few thousand kilometers at high latitudes, hot electrons in and above the auroral ionosphere, the correlation of auroral kilometric radiation with visual auroras and with Birkeland currents, electrostatic waves in the topside ionosphere, solitary waves and double layers, and an Alfven wave model of auroral arcs

  8. Theory of high temperature plasmas. Final report

    International Nuclear Information System (INIS)

    Davidson, R.C.; Liu, C.S.

    1977-01-01

    This is a report on the technical progress in our analytic studies of high-temperature fusion plasmas. We also emphasize that the research summarized here makes extensive use of computational methods and therefore forms a strong interface with our numerical modeling program which is discussed later in the report

  9. The AGS Booster high frequency rf system

    International Nuclear Information System (INIS)

    Sanders, R.T.; Cameron, P.; Eng, W.; Goldman, M.A.; Jablonski, E.; Kasha, D.; Keane, J.; McNerney, A.; Meth, M.; Plotkin, M.; Puglisi, M.; Ratti, A.; Spitz, R.

    1991-01-01

    A high level rf system, including a power amplifier and cavity, has been designed and built for the AGS Booster. It covers a frequency range of 2.4 to 4.2 MHz and will be used to accelerate high intensity protons. Low intensity polarized protons and heavy ions, to the 1.5 GeV level. A total accelerating voltage of up to 90 kV will be provided by two cavities, each having two gaps. The internally cross coupled, pushpull cavities are driven by an adjacently located power amplifier. In order to accommodate beam intensities up to 0.75 x 10 13 protons per bunch, a low plate resistance power tetrode is used. The tube anode is magnetically coupled to one of the cavity's two parallel cells. The amplifier is a grounded cathode configuration driven by a remotely located solid-state amplifier. It has been tested in the laboratory at full gap voltage with satisfactory results. 5 refs., 2 figs., 1 tab

  10. Double streamer phenomena in atmospheric pressure low frequency corona plasma

    International Nuclear Information System (INIS)

    Kim, Dan Bee; Jung, H.; Gweon, B.; Choe, Wonho

    2010-01-01

    Time-resolved images of an atmospheric pressure corona discharge, generated at 50 kHz in a single pin electrode source, show unique positive and negative corona discharge features: a streamer for the positive period and a glow for the negative period. However, unlike in previous reports of dc pulse and low frequency corona discharges, multistreamers were observed at the initial time stage of the positive corona. A possible physical mechanism for the multistreamers is suggested.

  11. Plasma polymerized high energy density dielectric films for capacitors

    Science.gov (United States)

    Yamagishi, F. G.

    1983-01-01

    High energy density polymeric dielectric films were prepared by plasma polymerization of a variety of gaseous monomers. This technique gives thin, reproducible, pinhole free, conformable, adherent, and insoluble coatings and overcomes the processing problems found in the preparation of thin films with bulk polymers. Thus, devices are prepared completely in a vacuum environment. The plasma polymerized films prepared all showed dielectric strengths of greater than 1000 kV/cm and in some cases values of greater than 4000 kV/cm were observed. The dielectric loss of all films was generally less than 1% at frequencies below 10 kHz, but this value increased at higher frequencies. All films were self healing. The dielectric strength was a function of the polymerization technique, whereas the dielectric constant varied with the structure of the starting material. Because of the thin films used (thickness in the submicron range) surface smoothness of the metal electrodes was found to be critical in obtaining high dielectric strengths. High dielectric strength graft copolymers were also prepared. Plasma polymerized ethane was found to be thermally stable up to 150 C in the presence of air and 250 C in the absence of air. No glass transitions were observed for this material.

  12. Major upgrades of the high frequency B-dot probe diagnostic suite on ASDEX Upgrade

    Directory of Open Access Journals (Sweden)

    Ochoukov Roman

    2017-01-01

    Full Text Available The high frequency B-dot (HFB probe diagnostic on the ASDEX Upgrade tokamak has undergone a considerable upgrade during the 2016 opening of the torus. The probe coverage is now greatly expanded toroidally, as well as radially with the addition of probes on the high field side and the removable manipulator head. A new 2-channel fast digitizer now allows to examine and record radio frequency (RF wave emissions emanating from the plasma in the ion cyclotron range of frequencies (ICRF. Possible studies that can be achieved now include: a study of core ICRF power absorption efficiency; a study of ion cyclotron emissions from the plasma generated by energetic ions; and study of ICRF wave/plasma turbulence interactions in the scrape-off layer region.

  13. Contact resistance measurement structures for high frequencies

    NARCIS (Netherlands)

    Roy, Deepu; Pijper, Ralf M.T.; Tiemeijer, Luuk F.; Wolters, Robertus A.M.

    2011-01-01

    Knowledge of the interfacial contact impedance offered by the device at its operating frequency range is crucial for accurate modelling and understanding of the device. In this article, a novel modified TLM test-structure has been devised to extract interfacial contact parameters at frequencies upto

  14. High beta plasmas in the PBX tokamak

    International Nuclear Information System (INIS)

    Bol, K.; Buchenauer, D.; Chance, M.

    1986-04-01

    Bean-shaped configurations favorable for high β discharges have been investigated in the Princeton Beta Experiment (PBX) tokamak. Strongly indented bean-shaped plasmas have been successfully formed, and beta values of over 5% have been obtained with 5 MW of injected neutral beam power. These high beta discharges still lie in the first stability regime for ballooning modes, and MHD stability analysis implicates the external kink as responsible for the present β limit

  15. High-throughput anisotropic plasma etching of polyimide for MEMS

    International Nuclear Information System (INIS)

    Bliznetsov, Vladimir; Manickam, Anbumalar; Ranganathan, Nagarajan; Chen, Junwei

    2011-01-01

    This note describes a new high-throughput process of polyimide etching for the fabrication of MEMS devices with an organic sacrificial layer approach. Using dual frequency superimposed capacitively coupled plasma we achieved a vertical profile of polyimide with an etching rate as high as 3.5 µm min −1 . After the fabrication of vertical structures in a polyimide material, additional steps were performed to fabricate structural elements of MEMS by deposition of a SiO 2 layer and performing release etching of polyimide. (technical note)

  16. SiOx Ink-Repellent Layer Deposited by Radio Frequency (RF) Plasmas in Continuous Wave and Pulse Mode

    International Nuclear Information System (INIS)

    Chen Qiang; Fu Yabo; Pang Hua; Zhang Yuefei; Zhang Guangqiu

    2007-01-01

    Low surface energy layers, proposed application for non-water printing in computer to plate (CTP) technology, are deposited in both continuous wave and pulse radio frequency (13.56 MHz) plasma with hexamethyldisiloxane (HMDSO) as precursor. It is found that the plasma mode dominates the polymer growth rate and the surface composition. Derived from the spectra of X-ray photoelectron spectroscopy (XPS) and combined with printable test it is concluded that concentration of Si in coatings plays an important role for the ink printability and the ink does not adhere on the surface with high silicon concentration

  17. Initial frequency shift of large amplitude plasma wave

    International Nuclear Information System (INIS)

    Sugihara, Ryo; Yamanaka, Kaoru.

    1979-04-01

    A distribution function which is an exact solution to the collisionless Boltzmann equation is obtained in an expansion form in terms of the potential phi(x, t). A complex nonlinear frequency shift ωsub( n)(t) is obtained by use of the Poisson equation and the expansion. The theory is valid for arbitrary phi 0 and v sub(p) as long as ωsub(p) >> γsub( l), and in the initial phase defined by 0 0 , v sub(p), ωsub(p), γsub( l) and t sub(c) are the initial value of phi, the phase velocity, the Langmuir frequency, the linear Landau damping coefficient and the time for the first minimum of the amplitude oscillation. The ωsub( n)(0) does not vanish and Reωsub( n)(0)/γsub( l) > 1 holds even for e phi 0 /T 1 in the initial phase for v sub( p) > v sub( t). The theory reproduces main features of experimental results and that of simulations. (author)

  18. Study and realisation of a high frequency analyzer; Etude et realisation d'un analyseur de signaux a haute frequence

    Energy Technology Data Exchange (ETDEWEB)

    Bourbigot, J [Commissariat a l' Energie Atomique, Fontenay aux Roses (France). Centre d' Etudes Nucleaires

    1966-07-01

    This device is designed for the amplitude and frequency analysis of electric or electromagnetic signals in the frequency range of 0 to 55 MHz. The frequency spectrum of a preset bandwidth is displayed on the screen of an oscilloscope. Conceived to analyse the electromagnetic oscillations that can be generated in a plasma, its main characteristics are the following: extended bandwidth of analysed frequencies, on both sides of the ion cyclotron frequency in a magnetic field up to 20 kGs; linear amplitude and frequency response; possibility of analysing a narrow band; high sensitivity; analysis repetition rate of 25 per second. The different parts of the analyzer are described after a discussion of the choice of the techniques used in their design. In addition to its present use, the device can be applied to perform all the functions of a commercial spectral analyzer. (author) [French] Cet appareil est destine a l'analyse en frequence et amplitude de signaux electriques ou electromagnetiques dans une gamme de frequences de 0 a 55 MHz. Couple a un oscillographe, il permet de faire apparaitre sur l'ecran, le spectre de frequences dans une gamme choisie. Etudie dans le but d'analyser les oscillations electromagnetiques pouvant apparaitre dans un plasma, ses principales caracteristiques sont les suivantes: une bande etendue de frequences analysees, de part et d'autre de la frequence cyclotronique des ions dans un champ magnetique pouvant atteindre 20 kGs (valeur maximum 55 MHz); une reponse lineaire en amplitude et en frequence; la possibilite d'analyser, une bande restreinte de frequences; une grande sensibilite La frequence d'analyse est de 25 periodes par seconde. Les diverses parties de l'analyseur sont decrites apres l'expose des motifs ayant guide le choix des solutions adoptees pour sa realisation. Les schemas electriques sont egalement presentes. En dehors du but precis qui a motive la realisation de cet appareil, son usage peut s'etendre a toutes les applications

  19. Transport in JET high performance plasmas

    International Nuclear Information System (INIS)

    2001-01-01

    Two type of high performance scenarios have been produced in JET during DTE1 campaign. One of them is the well known and extensively used in the past ELM-free hot ion H-mode scenario which has two distinct regions- plasma core and the edge transport barrier. The results obtained during DTE-1 campaign with D, DT and pure T plasmas confirms our previous conclusion that the core transport scales as a gyroBohm in the inner half of plasma volume, recovers its Bohm nature closer to the separatrix and behaves as ion neoclassical in the transport barrier. Measurements on the top of the barrier suggest that the width of the barrier is dependent upon isotope and moreover suggest that fast ions play a key role. The other high performance scenario is a relatively recently developed Optimised Shear Scenario with small or slightly negative magnetic shear in plasma core. Different mechanisms of Internal Transport Barrier (ITB) formation have been tested by predictive modelling and the results are compared with experimentally observed phenomena. The experimentally observed non-penetration of the heavy impurities through the strong ITB which contradicts to a prediction of the conventional neo-classical theory is discussed. (author)

  20. Transport in JET high performance plasmas

    International Nuclear Information System (INIS)

    1999-01-01

    Two type of high performance scenarios have been produced in JET during DTE1 campaign. One of them is the well known and extensively used in the past ELM-free hot ion H-mode scenario which has two distinct regions- plasma core and the edge transport barrier. The results obtained during DTE-1 campaign with D, DT and pure T plasmas confirms our previous conclusion that the core transport scales as a gyroBohm in the inner half of plasma volume, recovers its Bohm nature closer to the separatrix and behaves as ion neoclassical in the transport barrier. Measurements on the top of the barrier suggest that the width of the barrier is dependent upon isotope and moreover suggest that fast ions play a key role. The other high performance scenario is a relatively recently developed Optimised Shear Scenario with small or slightly negative magnetic shear in plasma core. Different mechanisms of Internal Transport Barrier (ITB) formation have been tested by predictive modelling and the results are compared with experimentally observed phenomena. The experimentally observed non-penetration of the heavy impurities through the strong ITB which contradicts to a prediction of the conventional neo-classical theory is discussed. (author)

  1. 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.

  2. The compact mirrors with high pressure plasmas

    International Nuclear Information System (INIS)

    Anikeev, A.V.; Bagryansky, P.A.; Ivanov, A.A.; Lizunov, A.A.; Murakhtin, S.V.; Prikhodko, V.V.; Collatz, S.; Noack, K.

    2004-01-01

    The gas dynamic trap (GDP) experimental facility at the Budker Institute Novosibirsk is a long axial-symmetric mirror system with a high mirror ratio variable in the range of 12.5 - 100 for the confinement of a two-component plasma. One component is a collisional plasma with ion and electron temperatures up to 100 eV and density up to 10 14 cm -3 . The second component is the population of high-energetic fast ions with energies of 2-18 keV and a density up to 10 13 cm -3 which is produced by neutral beam injection (NBI). GDP is currently undergoing an upgrade whose first stage is the achievement of the synthesized hot ion plasmoid experiment (SHIP). This experiment aims at the investigation of plasmas and at the knowledge of plasma parameters that have never been achieved before in magnetic mirrors. The paper presents the physical concept of the SHIP experiment, the results of numerical pre-calculations and draws conclusions regarding possible scenarios of experiments. The simulation of a maximal NBI power regime with hydrogen injection gave a fast ion density of 1.2*10 14 cm -3 with a mean energy of 14 keV. The calculation of the deuterium injection regime with 2 MW NBI power gave a maximal fast ion density of 1.9*10 14 cm -3 with a beam energy of 9 keV. The calculation of an experimental scenario with reduced magnetic field resulted in a maximal β-value of 62%, so this regime is recommended for the study of high-β effects in plasmas confined in axial-symmetric mirrors

  3. ANTENNA RADIATION NEAR THE LOCAL PLASMA FREQUENCY BY LANGMUIR WAVE EIGENMODES

    International Nuclear Information System (INIS)

    Malaspina, David M.; Cairns, Iver H.; Ergun, Robert E.

    2012-01-01

    Langmuir waves (LWs) in the solar wind are generated by electron beams associated with solar flares, interplanetary shock fronts, planetary bow shocks, and magnetic holes. In principle, LWs localized as eigenmodes of density fluctuations can emit electromagnetic (EM) radiation by an antenna mechanism near the local plasma frequency f p and twice the local plasma frequency. In this work, analytic expressions are derived for the radiated electric and magnetic fields and power generated near f p by LW eigenmodes. The EM wave power emitted near f p is predicted as a function of the eigenmode length scale L, maximum electric field, driving electron beam speed, and the ambient plasma density and temperature. The escape to a distant observer of f p radiation from a localized Langmuir eigenmode is also briefly explored as a function of the plasma conditions.

  4. Kinetic models of partially ionized complex plasmas in the low frequency regime

    International Nuclear Information System (INIS)

    Tolias, P.; Ratynskaia, S.; Angelis, U. de

    2011-01-01

    The results from three kinetic models of complex plasmas taking into account collisions with neutrals are compared in the low-frequency regime: The ''full'' model which considers the absorption of plasma fluxes on dust particles and dust charge fluctuations, the ''multi-component'' model where both these effects are neglected, and the ''standard'' model which takes into account the dust charge perturbations but not the absorption of fluxes. We derive and numerically evaluate expressions of the low frequency responses of these models, also taking into account the modification of the capture cross-sections due to the effect of neutrals. The role of plasma sources and collisions with neutrals is assessed by computing the plasma permittivities and static permittivities for all the three models.

  5. 1 μs broadband frequency sweeping reflectometry for plasma density and fluctuation profile measurements

    Science.gov (United States)

    Clairet, F.; Bottereau, C.; Medvedeva, A.; Molina, D.; Conway, G. D.; Silva, A.; Stroth, U.; ASDEX Upgrade Team; Tore Supra Team; Eurofusion Mst1 Team

    2017-11-01

    Frequency swept reflectometry has reached the symbolic value of 1 μs sweeping time; this performance has been made possible, thanks to an improved control of the ramp voltage driving the frequency source. In parallel, the memory depth of the acquisition system has been upgraded and can provide up to 200 000 signals during a plasma discharge. Additional improvements regarding the trigger delay determination of the acquisition and the voltage ramp linearity required by this ultra-fast technique have been set. While this diagnostic is traditionally dedicated to the plasma electron density profile measurement, such a fast sweeping rate can provide the study of fast plasma events and turbulence with unprecedented time and radial resolution from the edge to the core. Experimental results obtained on ASDEX Upgrade plasmas are presented to demonstrate the performances of the diagnostic.

  6. Low-frequency electrostatic dust-modes in a nonuniform magnetized dusty plasma

    International Nuclear Information System (INIS)

    Paul, S.K.; Duha, S.S.; Mamun, A.A.

    2004-07-01

    A self-consistent and general description of obliquely propagating low frequency electrostatic dust-modes in a inhomogeneous, magnetized dusty plasma system has been presented. A number of different situations, which correspond to different low-frequency electrostatic dust-modes, namely, dust-acoustic mode, dust-drift mode, dust-cyclotron mode, dust-lower-hybrid mode, and other associated modes (such as, accelerated and retarded dust-acoustic modes, accelerated and retarded dust-lower-hybrid modes, etc.), have also been investigated. It has been shown that the effects of obliqueness and inhomogeneities in plasma particle number densities introduce new electrostatic dust modes as well as significantly modify the dispersion properties of the other low-frequency electrostatic dust-modes. The implications of these results to some space and astrophysical dusty plasma systems, especially to planetary ring-systems and cometary tails, are briefly mentioned. (author)

  7. Application of Plasma Waveguides to High Energy Accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Milchberg, Howard M

    2013-03-30

    will continue our development of advanced simulation tools by modifying the QuickPIC algorithm to allow for the simulation of plasma particle pick-up by the wake fields. We have also performed extensive simulations of plasma slow wave structures for efficient THz generation by guided laser beams or accelerated electron beams. We will pursue experimental studies of direct laser acceleration, and THz generation by two methods, ponderomotive-induced THz polarization, and THz radiation by laser accelerated electron beams. We also plan to study both conventional and corrugated plasma channels using our new 30 TW in our new lab facilities. We will investigate production of very long hydrogen plasma waveguides (5 cm). We will study guiding at increasing power levels through the onset of laser-induced cavitation (bubble regime) to assess the role played by the preformed channel. Experiments in direct acceleration will be performed, using laser plasma wakefields as the electron injector. Finally, we will use 2-colour ionization of gases as a high frequency THz source (<60 THz) in order for femtosecond measurements of low plasma densities in waveguides and beams.

  8. Relationship between the induction frequency and LTE in inductively coupled plasmas

    International Nuclear Information System (INIS)

    Mostaghimi, J.; Boulos, M.I.

    1990-01-01

    In this paper, the effect of the induction frequency on the local thermodynamic equilibrium (LTE) conditions in an inductively coupled plasma is investigated. Using generators with frequencies ranging from 5 to 56 MHz, a previous study investigated demonstrated the importance of this effect. Their measurements of the excitation temperatures of the iron atomic lines showed a sharp decrease in this temperature as a result of the increase in frequency. Another conclusion was that, all other parameters constant, increase in frequency will help the promotion of non-LTE effects

  9. Absorption of low-frequency electromagnetic waves by plasma in electromagnetic trap

    International Nuclear Information System (INIS)

    D'yakov, V.E.

    1984-01-01

    Absorption of electromagnetic waves in plasma of the electromagnetic trap is investigated. An integro-differential equation describing the behaviour of the electrical and magnetic fields of the wave is obtained. The wave has a component along the plasma inhomogeneity axis. Solution of this equation is found within the low frequency range corresponding to the anomalous skin-effect. The possibility of ion-acoustic waves excitation is demonstrated. Expressions are found for reflection, absorption and transformation coefficients

  10. A Taiwanese food frequency questionnaire correlates with plasma docosahexaenoic acid but not with plasma eicosapentaenoic acid levels: questionnaires and plasma biomarkers.

    Science.gov (United States)

    Chien, Kuo-Liong; Lee, Meei-Shyuan; Tsai, Yi-Tsen; Chen, Pey-Rong; Lin, Hung-Ju; Hsu, Hsiu-Ching; Lee, Yuan-The; Chen, Ming-Fong

    2013-02-16

    Little evidence is available for the validity of dietary fish and polyunsaturated fatty acid intake derived from interviewer-administered questionnaires and plasma docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) concentration. We estimated the correlation of DHA and EPA intake from both questionnaires and biochemical measurements. Ethnic Chinese adults with a mean (± SD) age of 59.8 (±12.8) years (n = 297) (47% women) who completed a 38-item semi-quantitative food-frequency questionnaire and provided a plasma sample were enrolled. Plasma fatty acids were analyzed by capillary gas chromatography. The Spearmen rank correlation coefficients between the intake of various types of fish and marine n-3 fatty acids as well as plasma DHA were significant, ranging from 0.20 to 0.33 (P food frequency questionnaire, were correlated with the percentages of these fatty acids in plasma, and in particular with plasma DHA. Plasma DHA levels were correlated to dietary intake of long-chain n-3 fatty acids.

  11. Transverse ion energization and low-frequency plasma waves in the mid-altitude auroral zone - A case study

    Science.gov (United States)

    Peterson, W. K.; Shelley, E. G.; Boardsen, S. A.; Gurnett, D. A.; Ledley, B. G.; Sugiura, M.; Moore, T. E.

    1988-01-01

    Evidence of transverse ion energization at altitudes of several earth radii in the auroral zone was reexamined using several hundred hours of high-sensitivity and high-resolution plasma data obtained by the Dynamics Explorer 1 satellite. The data on particle environment encountered at midaltitudes in the auroral zone disclosed rapid variations in the values of total density, thermal structure, and composition of the plasma in the interval measured; the modes of low-frequency plasma waves also varied rapidly. It was not possible to unambiguously identify in these data particle and wave signature of local transverse ion energization; however, many intervals were found where local transverse ion heating was consistent with the observations.

  12. Low Frequency Plasma Oscillations in a 6-kW Magnetically Shielded Hall Thruster

    Science.gov (United States)

    Jorns, Benjamin A.; Hofery, Richard R.

    2013-01-01

    The oscillations from 0-100 kHz in a 6-kW magnetically shielded thruster are experimen- tally characterized. Changes in plasma parameters that result from the magnetic shielding of Hall thrusters have the potential to significantly alter thruster transients. A detailed investigation of the resulting oscillations is necessary both for the purpose of determin- ing the underlying physical processes governing time-dependent behavior in magnetically shielded thrusters as well as for improving thruster models. In this investigation, a high speed camera and a translating ion saturation probe are employed to examine the spatial extent and nature of oscillations from 0-100 kHz in the H6MS thruster. Two modes are identified at 8 kHz and 75-90 kHz. The low frequency mode is azimuthally uniform across the thruster face while the high frequency oscillation is concentrated close to the thruster centerline with an m = 1 azimuthal dependence. These experimental results are discussed in the context of wave theory as well as published observations from an unshielded variant of the H6MS thruster.

  13. Resistive wall mode stabilization in slowly rotating high beta plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Reimerdes, H [Columbia University, New York, NY 10027 (United States); Garofalo, A M [Columbia University, New York, NY 10027 (United States); Okabayashi, M [Princeton Plasma Physics Laboratory, Princeton, NJ 08543-0451 (United States); Strait, E J [General Atomics, San Diego, CA 92186-5608 (United States); Betti, R [University of Rochester, Rochester, NY 14627 (United States); Chu, M S [General Atomics, San Diego, CA 92186-5608 (United States); Hu, B [University of Rochester, Rochester, NY 14627 (United States); In, Y [FAR-TECH, Inc., San Diego, CA 92121 (United States); Jackson, G L [General Atomics, San Diego, CA 92186-5608 (United States); La Haye, R J [General Atomics, San Diego, CA 92186-5608 (United States); Lanctot, M J [Columbia University, New York, NY 10027 (United States); Liu, Y Q [Chalmers University of Technology, S-412 96 Goeteborg (Sweden); Navratil, G A [Columbia University, New York, NY 10027 (United States); Solomon, W M [Princeton Plasma Physics Laboratory, Princeton, NJ 08543-0451 (United States); Takahashi, H [Princeton Plasma Physics Laboratory, Princeton, NJ 08543-0451 (United States); Groebner, R J [General Atomics, San Diego, CA 92186-5608 (United States)

    2007-12-15

    DIII-D experiments show that the resistive wall mode (RWM) can remain stable in high {beta} scenarios despite a low net torque from nearly balanced neutral beam injection heating. The minimization of magnetic field asymmetries is essential for operation at the resulting low plasma rotation of less than 20 krad s{sup -1} (measured with charge exchange recombination spectroscopy using C VI emission) corresponding to less than 1% of the Alfven velocity or less than 10% of the ion thermal velocity. In the presence of n = 1 field asymmetries the rotation required for stability is significantly higher and depends on the torque input and momentum confinement, which suggests that a loss of torque-balance can lead to an effective rotation threshold above the linear RWM stability threshold. Without an externally applied field the measured rotation can be too low to neglect the diamagnetic rotation. A comparison of the instability onset in plasmas rotating with and against the direction of the plasma current indicates the importance of the toroidal flow driven by the radial electric field in the stabilization process. Observed rotation thresholds are compared with predictions for the semi-kinetic damping model, which generally underestimates the rotation required for stability. A more detailed modeling of kinetic damping including diamagnetic and precession drift frequencies can lead to stability without plasma rotation. However, even with corrected error fields and fast plasma rotation, plasma generated perturbations, such as edge localized modes, can nonlinearly destabilize the RWM. In these cases feedback control can increase the damping of the magnetic perturbation and is effective in extending the duration of high {beta} discharges.

  14. HIGH FREQUENCY INDUCTION WELDING OF HIGH SILICON STEEL TUBES

    Directory of Open Access Journals (Sweden)

    Ricardo Miranda Alé

    2012-06-01

    Full Text Available High-Si steel is a low cost alternative for the fabrication of tubular structures resistant to atmospheric corrosion. However, the literature has often pointed out that steels presenting a higher Si content and/or a lower Mn/Si ratio have higher susceptibility to defects at the weld bond line during HFIW (High Frequency Induction Welding process, which has been widely used for manufacturing small diameter tubes. In this study the effect of the HFIW conditions on the quality of steel tubes with high-Si content and low Mn/Si ratio is investigated. The quality of welded tubes was determined by flare test and the defects in the bond line were identified by SEM. It has been found that higher welding speeds, V-convergence angles and power input should be applied in welding of high-Si steel, when compared to similar strength C-Mn steel.

  15. Study of geometrical and operational parameters controlling the low frequency microjet atmospheric pressure plasma characteristics

    International Nuclear Information System (INIS)

    Kim, Dan Bee; Rhee, J. K.; Moon, S. Y.; Choe, W.

    2006-01-01

    Controllability of small size atmospheric pressure plasma generated at low frequency in a pin to dielectric plane electrode configuration was studied. It was shown that the plasma characteristics could be controlled by geometrical and operational parameters of the experiment. Under most circumstances, continuous glow discharges were observed, but both the corona and/or the dielectric barrier discharge characteristics were observed depending on the position of the pin electrode. The plasma size and the rotational temperature were also varied by the parameters. The rotational temperature was between 300 and 490 K, being low enough to treat thermally sensitive materials

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

    Energy Technology Data Exchange (ETDEWEB)

    Maehara, Tsunehiro, E-mail: maehara@phys.sci.ehime-u.ac.jp [Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan); Nishiyama, Kyohei; Onishi, Shingo; Mukasa, Shinobu; Toyota, Hiromichi [Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan); Kuramoto, Makoto [Integrated Center for Science, Ehime University, Matsuyama 790-8577 (Japan); Nomura, Shinfuku [Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan); Kawashima, Ayato [Faculty of Agriculture, Ehime University, Matsuyama 790-8566 (Japan)

    2010-02-15

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

  17. Numerical Simulation of Spheroidization Process of TiAl Alloy Powders in Radio Frequency Plasma

    Directory of Open Access Journals (Sweden)

    ZHU Langping

    2017-06-01

    Full Text Available A numerical simulation method was used to study the radio frequency plasma spheroidization process of TiAl alloy powder. The effects of velocity field and temperature field on the motion trajectory and mass change of TiAl alloy powder with different particle size were analyzed.The results show that the temperature of powder particles increases rapidly under high temperature plasma, surface evaporation cause the reduction of particle size, and particles with small size tend to evaporate quickly. The motion trajectory of particles with different sizes in the lower end of the cooling tube is different obviously, small particles tend to enter the air outlet,while the larger particles are easy to fall down to the bottom of the cooling tube to be collected. Increasing air flow rate can improve the velocity of air flow in the spheroidizing system, causing larger particles to be taken away by the air, resulting in yield reduction. The simulation results of TiAl alloy powder spheroidization are close to the experimental results refer to parameters such as powder size distribution, average particle size and powder yield, and the model is in good accordance with the actual process of the spheroidization.

  18. Low frequency fluid drift turbulence in magnetised plasmas

    International Nuclear Information System (INIS)

    Scott, B.

    2001-03-01

    We start with the first principles of fluid dynamics and classical electrodynamics and then find the regime in which we can reduce to quasineutral dynamics, which also implicitly underlies MHD. Then, we find the limits under which we can specialise to the MHD model as a subset, first of two fluid dynamics, then of the fluid drift dynamics that results when the motions are not vigorous enough to compress the magnetic field. In Chapters 4 and 5 we find the basic character of small disturbances in this system. Chapters 6 through 9 treat various aspects of fluid drift turbulence, also called drift wave turbulence, moving from a simple consideration of the underlying nonlinear dynamics, to some methods by which one can diagnose computations to find out what is going on, and then to the nonlinear instability which is the hallmark of this physics, and then to the interactions with large scale sheared flows. Chapter 10 introduces interchange turbulence, which is the plasma analog of the buoyant convection well known from fluid dynamics. Chapters 11 through 13 treat electromagnetic drift wave turbulence in closed magnetic field geometry, starting with a simplified model treating only the electron pressure and then introducing the electron and ion temperatures. Chapter 14 treats the basic characteristics of the transport that results from fluid drift turbulence, as this is quite different from the kinetic diffusion, such as heat conduction, that is more familiar. Appendices A and B treat the details of the numerical methods and models of magnetic field geometry necessary to treat all but the simplest cases. For this subject is dominated by nonlinear physics and therefore numerical computation. Computations therefore form an integral part of its study right from the beginning. Citations to the literature are not intended to be comprehensive but to serve as starting points for further reading, a section for which is included in every chapter. Much of this work is very new, and

  19. Modulated convection at high frequencies and large modulation amplitudes

    International Nuclear Information System (INIS)

    Swift, J.B.; Hohenberg, P.C.

    1987-01-01

    Modulated Rayleigh-Benard convection is analyzed for high frequencies and large modulation amplitudes. The linear theory of Gershuni and Zhukhovitskii is generalized to the nonlinear domain, and a subcritical bifurcation to convection is found in agreement with the experiments of Niemela and Donnelly. The crossover between the high-frequency (''Stokes layer'') regime and the low-frequency regime studied previously is analyzed

  20. Calculation of Leakage Inductance for High Frequency Transformers

    DEFF Research Database (Denmark)

    Ouyang, Ziwei; Jun, Zhang; Hurley, William Gerard

    2015-01-01

    Frequency dependent leakage inductance is often observed. High frequency eddy current effects cause a reduction in leakage inductance. The proximity effect between adjacent layers is responsible for the reduction of leakage inductance. This paper gives a detailed analysis of high frequency leakag...

  1. Low frequency, electrodynamic simulation of kinetic plasmas with the DArwin Direct Implicit Particle-In-Cell (DADIPIC) method

    International Nuclear Information System (INIS)

    Gibbons, M.R.

    1995-06-01

    This dissertation describes a new algorithm for simulating low frequency, kinetic phenomena in plasmas. DArwin Direct Implicit Particle-in-Cell (DADIPIC), as its name implies, is a combination of the Darwin and direct implicit methods. One of the difficulties in simulating plasmas lies in the enormous disparity between the fundamental scale lengths of a plasma and the scale lengths of the phenomena of interest. The objective is to create models which can ignore the fundamental constraints without eliminating relevant plasma properties. Over the past twenty years several PIC methods have been investigated for overcoming the constraints on explicit electrodynamic PIC. These models eliminate selected high frequency plasma phenomena while retaining kinetic phenomena at low frequency. This dissertation shows that the combination of Darwin and Direct Implicit allows them to operate better than they have been shown to operate in the past. Through the Darwin method the hyperbolic Maxwell's equations are reformulated into a set of elliptic equations. Propagating light waves do not exist in the formulation so the Courant constraint on the time step is eliminated. The Direct Implicit method is applied only to the electrostatic field with the result that electrostatic plasma oscillations do not have to be resolved for stability. With the elimination of these constraints spatial and temporal discretization can be much larger than that possible with explicit, electrodynamic PIC. The code functions in a two dimensional Cartesian region and has been implemented with all components of the particle velocities, the E-field, and the B-field. Internal structures, conductors or dielectrics, may be placed in the simulation region, can be set at desired potentials, and driven with specified currents

  2. RF-heating of plasma in the frequency domain of the ion cyclotron harmonics

    International Nuclear Information System (INIS)

    Hahnekamp, H.G.; Stampa, A.; Tuczek, H.; Laeuter, R.; Wulf, H.O.

    1976-01-01

    Experiments on rf-heating of plasmas in the frequency domain of the ion cyclotron harmonics are reported. The rf-power is coupled to the magneto-acoustic wave for frequencies between ωsub(ci) and 5ωsub(ci). The measurements indicate that the damping of the pump wave is mainly due to the excitation of turbulence, whereas direct resonance at 2ωsub(ci) seems to be of minor importance

  3. An inkjet vision measurement technique for high-frequency jetting

    International Nuclear Information System (INIS)

    Kwon, Kye-Si; Jang, Min-Hyuck; Park, Ha Yeong; Ko, Hyun-Seok

    2014-01-01

    Inkjet technology has been used as manufacturing a tool for printed electronics. To increase the productivity, the jetting frequency needs to be increased. When using high-frequency jetting, the printed pattern quality could be non-uniform since the jetting performance characteristics including the jetting speed and droplet volume could vary significantly with increases in jet frequency. Therefore, high-frequency jetting behavior must be evaluated properly for improvement. However, it is difficult to measure high-frequency jetting behavior using previous vision analysis methods, because subsequent droplets are close or even merged. In this paper, we present vision measurement techniques to evaluate the drop formation of high-frequency jetting. The proposed method is based on tracking target droplets such that subsequent droplets can be excluded in the image analysis by focusing on the target droplet. Finally, a frequency sweeping method for jetting speed and droplet volume is presented to understand the overall jetting frequency effects on jetting performance

  4. An inkjet vision measurement technique for high-frequency jetting

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Kye-Si, E-mail: kskwon@sch.ac.kr; Jang, Min-Hyuck; Park, Ha Yeong [Department of Mechanical Engineering, Soonchunhyang University 22, Soonchunhyang-Ro, Shinchang, Asan Chungnam 336-745 (Korea, Republic of); Ko, Hyun-Seok [Department of Electrical and Robot Engineering, Soonchunhyang University, 22, Soonchunhyang-Ro, Shinchang, Asan Chungnam 336-745 (Korea, Republic of)

    2014-06-15

    Inkjet technology has been used as manufacturing a tool for printed electronics. To increase the productivity, the jetting frequency needs to be increased. When using high-frequency jetting, the printed pattern quality could be non-uniform since the jetting performance characteristics including the jetting speed and droplet volume could vary significantly with increases in jet frequency. Therefore, high-frequency jetting behavior must be evaluated properly for improvement. However, it is difficult to measure high-frequency jetting behavior using previous vision analysis methods, because subsequent droplets are close or even merged. In this paper, we present vision measurement techniques to evaluate the drop formation of high-frequency jetting. The proposed method is based on tracking target droplets such that subsequent droplets can be excluded in the image analysis by focusing on the target droplet. Finally, a frequency sweeping method for jetting speed and droplet volume is presented to understand the overall jetting frequency effects on jetting performance.

  5. Frequency stabilization of a He-Ne gas laser by controlling refractive index of laser plasma

    International Nuclear Information System (INIS)

    Xie Yi; Wu Yizun

    1991-01-01

    A new way to stabilize the frequency of a Zeeman He-Ne gas laser is described. The laser frequency is stabilized by controlling the refractive index of the laser plasma. It does not need a gas laser tube with a piezoelectric ceramic (PZT) made by special technology. As the phase-locking technology is used in the laser servo system, the self-beat frequency is a constant and the frequency stability is better than 2.2 x 10 -11 (averaging time = 10 sec.). The long term frequency fluctuation never exceeded 2 x 10 -8 during two months. The frequency of the locked point can be adjusted continuously in the range of over 200 MHz

  6. Observation of radio frequency ring-shaped hollow cathode discharge plasma with MgO and Al electrodes for plasma processing

    International Nuclear Information System (INIS)

    Ohtsu, Yasunori; Matsumoto, Naoki

    2014-01-01

    Various high-density plasma sources have been proposed for plasma processing. Especially, the hollow cathode discharge is one of the powerful ones. In this work, radio-frequency (RF) driven ring-shaped hollow cathode discharges with high secondary-electron emission have been investigated, using an aluminum (Al) cathode, coated or not with magnesium oxide (MgO). The thickness of MgO thin film is approximately 200 nm. The RF discharge voltage for the coated cathode is almost the same as that for the uncoated one, in a wide range of Ar gas pressure, from 5.3 to 53.2 Pa. The results reveal that the plasma density has a peak at an Ar gas pressure of 10.6 Pa for both cathodes. The plasma density for the coated cathode is about 1.5–3 times higher than that for the uncoated one, at various gas pressures. To the contrary, the electron temperature for the coated cathode is lower than temperature obtained with the uncoated cathode, at various gas pressures. Radial profiles of electron saturation current, which is proportional to plasma flux, are also examined for a wide range of gas pressure. Radial profiles of electron temperature at various axial positions are almost uniform for both cathodes so that the diffusion process due to density gradient is dominant for plasma transport. The secondary electrons emitted from the coated cathode contribute to the improvement of the plasma flux radial profile obtained using the uncoated cathode

  7. The potential for very high-frequency gravitational wave detection

    International Nuclear Information System (INIS)

    Cruise, A M

    2012-01-01

    The science case for observing gravitational waves at frequencies in the millihertz-kilohertz range using LIGO, VIRGO, GEO600 or LISA is very strong and the first results are expected at these frequencies. However, as gravitational wave astronomy progresses beyond the first detections, other frequency bands may be worth exploring. Early predictions of gravitational wave emission from discrete sources at very much higher frequencies (megahertz and above) have been published and more recent studies of cosmological signals from inflation, Kaluza-Klein modes from gravitational interactions in brane worlds and plasma instabilities surrounding violent astrophysical events, are all possible sources. This communication examines current observational possibilities and the detector technology required to make meaningful observations at these frequencies. (paper)

  8. High-speed photography application to pulsed hot plasma investigation

    International Nuclear Information System (INIS)

    Borov'etskij, M.; Koz'yarkevich, V.; Skrzhechanovskij, V.; Socha, R.

    1986-01-01

    Plasma focus is investigated using an electron-optical chamber for high-speed photography (KSK-1). Experimental devices for studying dynamics and structure of a plasma layer in the chosen interval, recording plasma spectra with time resolution as well as for studying the dynamics and structure of a plasma layer by Schlieren- and shadow methods are briefly described. Experimental results are presented

  9. Noise Suppression and Enhanced Focusability in Plasma Raman Amplifier with Multi-frequency Pump

    International Nuclear Information System (INIS)

    Balakin, A.A.; Fraiman, G.M.; Fisch, N.J.; Malkin, V.M.

    2003-01-01

    Laser pulse compression/amplification through Raman backscattering in plasmas can be facilitated by using multi-frequency pump laser beams. The efficiency of amplification is increased by suppressing the Raman instability of thermal fluctuations and seed precursors. Also the focusability of the amplified radiation is enhanced due to the suppression of large-scale longitudinal speckles in the pump wave structure

  10. Determination of the electron-electron collisional frequency by means of plasma electron spectroscopy

    International Nuclear Information System (INIS)

    Kolokolov, N.B.; Kudryavtsev, A.A.; Romanenko, V.A.

    1989-01-01

    Methods of controlling fast part of electron distribution function (DF) in nonlocal regime of current-free plasma are suggested and realized. Artificially created step in DF fast part has a simple link with frequencies of electron-electron and elastic electron-atom collisions that may be defined in the corresponding experiments

  11. Effect of frequency variation on electromagnetic pulse interaction with charges and plasma

    NARCIS (Netherlands)

    Khachatryan, A.G.; van Goor, F.A.; Verschuur, Jeroen W.J.; Boller, Klaus J.

    2005-01-01

    The effect of frequency variation (chirp) in an electromagnetic (EM) pulse on the pulse interaction with a charged particle and plasma is studied. Various types of chirp and pulse envelopes are considered. In vacuum, a charged particle receives a kick in the polarization direction after interaction

  12. The effect of toroidal plasma rotation on low-frequency reversed shear Alfven eigenmodes in tokamaks

    NARCIS (Netherlands)

    Haverkort, J. W.

    2012-01-01

    The influence of toroidal plasma rotation on the existence of reversed shear Alfven eigenmodes (RSAEs) near their minimum frequency is investigated analytically. An existence condition is derived showing that a radially decreasing kinetic energy density is unfavourable for the existence of RSAEs.

  13. Characteristic frequencies of a non-Maxwellian plasma - A method for localizing the exact frequencies of magnetospheric intense natural waves near fpe

    International Nuclear Information System (INIS)

    Belmont, G.

    1981-01-01

    Intense natural waves are commonly observed onboard satellites in the outer earth's magnetosphere, inside a narrow frequency range, including the electron plasma and upper hybrid frequencies. In order to progress in the understanding of their emission processes, it is necessary to determine precisely the relationship which exists between their frequencies and the characteristic frequencies of the magnetospheric plasma. For this purpose, it is necessary to take into account the fact that some of these characteristic frequencies, which are provided by active sounding of the plasma, not only depend on the total density, but also on the shape of the distribution function (which has generally been assumed to be Maxwellian). A method providing a fine diagnosis of general non-Maxwellian plasmas is developed. This method of analysis of the experimental data is based on a theoretical study which points out the influence of the shape of the distribution function on the dispersion curves (for wave vectors perpendicular to the static magnetic field)

  14. A study on the heating and diagnostic of a tokamak plasma by electromagnetic waves of the electron cyclotron range of frequencies

    International Nuclear Information System (INIS)

    Hoshino, Katsumichi

    1989-09-01

    A study on the heating and diagnosis of tokamak plasma by electromagnetic waves of electron cyclotron range of frequency is summarized. The main results obtained are as follows. On the engineering and technology, the technology of injecting high frequency, large power millimeter waves into tokamak plasma was established by carrying out the design, manufacture and test of a 60 GHz, 400 kW high frequency heating system, and the design, manufacture and test of a heterodyne type electron cyclotron radiation multi-channel mealsuring system were carried out, and the technology of measuring the radiation from tokamak plasma with the time resolution of 10 μs in multi-channel was established. On nuclear fusion reactor core engineering and plasma physics, the high efficiency electron heating of tokamak plasma by the incidence of fundamental irregular and regular waves at electron cyclotron frequency was verified. The discovery and analysis of the heating by electrostatic waves arising due to mode transformation from electromagnetic waves in upper hybrid resonance layer were carried out. By the incidence of second harmonic waves, the high efficiency electron heating of tokamak plasma was verified, and the heating characteristics were clarified. And others. (K.I.) 179 refs

  15. Dynamics of r.f. production of Stellarator plasmas in the ion cyclotron range of frequency

    International Nuclear Information System (INIS)

    Moiseenko, V.E.; Lysoivan, A.I.; Kasilov, S.V.; Plyusnin, V.V.

    1995-01-01

    The present study investigated numerically the process of r.f. production of plasma in the URAGAN-3M torsatron in the frequency range below the ion cyclotron frequency (ω ci ). The dynamics of r.f. plasma build-up at the stages of neutral gas burnout and plasma heating were studied using a zero-dimensional transport code, in which the plasma confinement law was determined by large helical device scaling. Two models for input r.f. power were used. In the first case, the r.f. power absorbed by the electrons was computed by a one-dimensional r.f. code solving Maxwell's boundary problem equations. The mechanisms of electron heating through direct excitation of the slow wave (SW) by antennae as well as the conversion of fast wave (FW) into SW in the vicinity of Alfven resonance (scenario of Alfven heating) were taken into account in the computations. In the second case, an 'ideal' model of r.f. power deposition onto the electrons as a linear function of plasma density was employed. A noticeable difference in plasma production dynamics computed for these two cases was found. Better agreement with experimental data obtained from the URAGAN-3M torsatron was found for the first case resulting from combination of the one-dimensional r.f. and zero-dimensional transport codes. ((orig.))

  16. State-space modeling of the radio frequency inductively-coupled plasma generator

    International Nuclear Information System (INIS)

    Dewangan, Rakesh Kumar; Punjabi, Sangeeta B; Mangalvedekar, H A; Lande, B K; Joshi, N K; Barve, D N

    2010-01-01

    Computational fluid dynamics models of RF-ICP are useful in understanding the basic transport phenomenon in an ICP torch under a wide variety of operating conditions. However, these models lack the ability to evaluate the effects of the plasma condition on the RF generator. In this paper, simulation of an induction plasma generator has been done using state space modelling by considering inductively coupled plasma as a part of RF network .The time dependent response of the RF-ICP generator circuit to given input excitation has been computed by extracting the circuit's state-space variables and their constraint matrices. MATLAB 7.1 software has been used to solve the state equations. The values of RF coil current, frequency and plasma power has been measured experimentally also at different plate bias voltage. The simulated model is able to predict RF coil current, frequency, plasma power, overall efficiency of the generator. The simulated and measured values are in agreement with each other. This model can prove useful as a design tool for the Induction plasma generator.

  17. An integrative time-varying frequency detection and channel sounding method for dynamic plasma sheath

    Science.gov (United States)

    Shi, Lei; Yao, Bo; Zhao, Lei; Liu, Xiaotong; Yang, Min; Liu, Yanming

    2018-01-01

    The plasma sheath-surrounded hypersonic vehicle is a dynamic and time-varying medium and it is almost impossible to calculate time-varying physical parameters directly. The in-fight detection of the time-varying degree is important to understand the dynamic nature of the physical parameters and their effect on re-entry communication. In this paper, a constant envelope zero autocorrelation (CAZAC) sequence based on time-varying frequency detection and channel sounding method is proposed to detect the plasma sheath electronic density time-varying property and wireless channel characteristic. The proposed method utilizes the CAZAC sequence, which has excellent autocorrelation and spread gain characteristics, to realize dynamic time-varying detection/channel sounding under low signal-to-noise ratio in the plasma sheath environment. Theoretical simulation under a typical time-varying radio channel shows that the proposed method is capable of detecting time-variation frequency up to 200 kHz and can trace the channel amplitude and phase in the time domain well under -10 dB. Experimental results conducted in the RF modulation discharge plasma device verified the time variation detection ability in practical dynamic plasma sheath. Meanwhile, nonlinear phenomenon of dynamic plasma sheath on communication signal is observed thorough channel sounding result.

  18. High-frequency analog integrated circuit design

    CERN Document Server

    1995-01-01

    To learn more about designing analog integrated circuits (ICs) at microwave frequencies using GaAs materials, turn to this text and reference. It addresses GaAs MESFET-based IC processing. Describes the newfound ability to apply silicon analog design techniques to reliable GaAs materials and devices which, until now, was only available through technical papers scattered throughout hundred of articles in dozens of professional journals.

  19. Coplanar stripline components for high frequency application

    Science.gov (United States)

    Goverdhanam, Kavita; Simons, Rainee N.; Dib, Nihad; Katehi, Linda P. B.

    1996-01-01

    In this paper, coplanar stripline discontinuities such as a slit, a right angle bend and a T-junction are characterized and their performance is parameterized with respect to frequency and geometry. Lumped equivalent circuits are presented for some of them. The element values are obtained from the measured discontinuity scattering (S) parameters. The experimental results are compared with theoretical data obtained using the Finite Difference Time Domain (FD-TD) technique for validation and show very good agreement.

  20. Ultra-low-frequency electrostatic modes in a magnetized dusty plasma

    International Nuclear Information System (INIS)

    Salimullah, M.; Amin, M.R.; Roy Chowdhury, A.R.; Salahuddin, M.

    1997-11-01

    A study on the extremely low-frequency possible electrostatic modes in a finite temperature magnetized dusty plasma taking the charged dust grains as the third component has been carried out using the appropriate Vlasov-kinetic theory for the dynamics of the electrons, ions and the dust particles. It is found that the inequalities of charge and number density of plasma species, and the finite-Larmor-radius thermal kinetic effects of the mobile charged dust grains, introduce the existence of very low-frequency electrostatic eigenmodes in the three-component homogeneous magnetized dusty plasma. The relevance of the present investigation to space and astrophysical situations as well as laboratory experiments for dust Coulomb crystallization has been pointed out. (author)

  1. Etching mechanism of niobium in coaxial Ar/Cl2 radio frequency plasma

    International Nuclear Information System (INIS)

    Upadhyay, J.; Im, Do; Popović, S.; Vušković, L.; Valente-Feliciano, A.-M.; Phillips, L.

    2015-01-01

    The understanding of the Ar/Cl 2 plasma etching mechanism is crucial for the desired modification of inner surface of the three dimensional niobium (Nb) superconductive radio frequency cavities. Uniform mass removal in cylindrical shaped structures is a challenging task because the etch rate varies along the direction of gas flow. The study is performed in the asymmetric coaxial radio-frequency (rf) discharge with two identical Nb rings acting as a part of the outer electrode. The dependence of etch rate uniformity on pressure, rf power, dc bias, Cl 2 concentration, diameter of the inner electrode, temperature of the outer cylinder, and position of the samples in the structure is determined. To understand the plasma etching mechanisms, we have studied several factors that have important influence on the etch rate and uniformity, which include the plasma sheath potential, Nb surface temperature, and the gas flow rate

  2. Etching mechanism of niobium in coaxial Ar/Cl2 radio frequency plasma

    Energy Technology Data Exchange (ETDEWEB)

    Upadhyay, Janardan [Old Dominion Univ., Norfolk, VA (United States); Im, Do [Old Dominion Univ., Norfolk, VA (United States); Popovic, Svetozar [Old Dominion Univ., Norfolk, VA (United States); Valente-Feliciano, Anne -Marie [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Phillips, H. Larry [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Vuskovic, Leposova [Old Dominion Univ., Norfolk, VA (United States)

    2015-03-18

    The understanding of the Ar/Cl2 plasma etching mechanism is crucial for the desired modification of inner surface of the three dimensional niobium (Nb) superconductive radio frequency cavities. Uniform mass removal in cylindrical shaped structures is a challenging task because the etch rate varies along the direction of gas flow. The study is performed in the asymmetric coaxial radio-frequency (rf) discharge with two identical Nb rings acting as a part of the outer electrode. The dependence of etch rate uniformity on pressure, rf power, dc bias, Cl2 concentration, diameter of the inner electrode, temperature of the outer cylinder, and position of the samples in the structure is determined. Furthermore, to understand the plasma etching mechanisms, we have studied several factors that have important influence on the etch rate and uniformity, which include the plasma sheath potential, Nb surface temperature, and the gas flow rate.

  3. Modelling of plasma-antenna coupling and non-linear radio frequency wave-plasma-wall interactions in the magnetized plasma device under ion cyclotron range of frequencies

    International Nuclear Information System (INIS)

    Lu, LingFeng

    2016-01-01

    Ion Cyclotron Resonant Heating (ICRH) by waves in 30-80 MHz range is currently used in magnetic fusion plasmas. Excited by phased arrays of current straps at the plasma periphery, these waves exist under two polarizations. The Fast Wave tunnels through the tenuous plasma edge and propagates to its center where it is absorbed. The parasitically emitted Slow Wave only exists close to the launchers. How much power can be coupled to the center with 1 A current on the straps? How do the emitted radiofrequency (RF) near and far fields interact parasitically with the edge plasma via RF sheath rectification at plasma-wall interfaces? To address these two issues simultaneously, in realistic geometry over the size of ICRH antennas, this thesis upgraded and tested the Self-consistent Sheaths and Waves for ICH (SSWICH) code. SSWICH couples self-consistently RF wave propagation and Direct Current (DC) plasma biasing via non-linear RF and DC sheath boundary conditions (SBCs) at plasma/wall interfaces. Its upgrade is full wave and was implemented in two dimensions (toroidal/radial). New SBCs coupling the two polarizations were derived and implemented along shaped walls tilted with respect to the confinement magnetic field. Using this new tool in the absence of SBCs, we studied the impact of a density decaying continuously inside the antenna box and across the Lower Hybrid (LH) resonance. Up to the memory limits of our workstation, the RF fields below the LH resonance changed with the grid size. However the coupled power spectrum hardly evolved and was only weakly affected by the density inside the box. In presence of SBCs, SSWICH-FW simulations have identified the role of the fast wave on RF sheath excitation and reproduced some key experimental observations. SSWICH-FW was finally adapted to conduct the first electromagnetic and RF-sheath 2D simulations of the cylindrical magnetized plasma device ALINE. (author) [fr

  4. Atomic processes in high temperature plasmas

    International Nuclear Information System (INIS)

    Hahn, Y.

    1991-07-01

    This is the final report on the project Atomic Processes in High Temperature Plasmas', which has been completed in June 30, 1991. The original contract started in 1978. The dielectronic recombination (DR) rate coefficients were calculated for ions with the number of electrons N = 1, 2, 3, 4, 5, 10, 11, and 12. The result was then used to construct a new and improved rate formula. Other important resonant processes, which are closely related to DR, were also studied to interpret experiments and to test the DR theory. The plasma field and the density effects on the rate coefficients was found to be important, and a consistent correction procedure is being developed. The available data on the DR rates and their accuracy do not yet fully meet the requirement for plasma modeling; there are serious gaps in the available data, and the currently adopted theoretical procedure needs improvements. Critical assessment of the current status of the DR problem is presented, and possible future work needed is summarized

  5. Analytic analysis on asymmetrical micro arcing in high plasma potential RF plasma systems

    International Nuclear Information System (INIS)

    Yin, Y; McKenzie, D R; Bilek, M M M

    2006-01-01

    We report experimental and analytical results on asymmetrical micro arcing in a RF (radio frequency) plasma. Micro arcing, resulting from high plasma potential, in RF plasma was found to occur only on the grounded electrode for a variety of electrode and surface configurations. The analytic derivation was based on a simple RF time-dependent Child-Langmuir sheath model and electric current continuity. We found that the minimum potential difference in one RF period across the grounded electrode sheath depends on the area ratio of the grounded electrode to the powered electrode. As the area ratio increases, the minimum potential difference across a sheath increases for the grounded electrode but not for the RF powered electrode. We showed that discharge time in micro arcing is more than 100 RF periods; thus the presence of a continuous high electric field in one RF cycle results in micro arcing on the grounded electrode. However, the minimum potential difference in one RF period across the powered electrode sheath is always small so that it prevents micro arcing occurring even though the average sheath voltage can be large. This simple analytic model is consistent with particle-in-cell simulation results

  6. Electrostatic noise bands associated with the electron gyrofrequency and plasma frequency in the outer magnetosphere

    International Nuclear Information System (INIS)

    Shaw, R.R.

    1975-01-01

    Naturally occurring noise bands near the electron plasma frequency are frequently detected by the University of Iowa plasma wave experiment on the IMP 6 satellite in the region from just inside the plasmapause to radial distances of about 10 earth radii in the outer magnetosphere. The electric field strength of these noise bands is usually small with electric field spectral densities near 10 -15 volts 2 meter -2 Hz -1 . A wave magnetic field has been detected only in a few unusually intense cases, and in these cases the magnetic field energy density is several orders of magnitude smaller than the electric field energy density. The bands are observed at all magnetic latitudes covered by the IMP 6 orbit (parallelγ/sub m/parallel less than or equal to 45 0 ) and appear to be a permanent feature of the outer magnetosphere. They are found at all local times and occur least frequently in the quadrant from 18 to 24 hours. The bands appear to consist of two distinct spectral types, diffuse and narrow. In both types the center frequency of the noise band is bounded by consecutive harmonics of the electron gyrofrequency, and the bands occur most often between harmonics that are near the local electron plasma frequency. These bands appear to merge continuously into two types of plasma wave emissions that are found in dissimilar regions of the magnetosphere (upper hybrid resonance noise, also called Region 3 noise, inside the plasmasphere and (n + 1/2)f/sub g/ harmonics in the outer magnetosphere). It is suggested that this smooth merging is caused by changes in the plasma wave dispersion relation that occur as the spacecraft moves from the cold plasma within the plasmasphere into the warm non-Maxwellian plasma found in the outer magnetosphere

  7. 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

  8. A study of three-half-turn and frame antennae for ion cyclotron range of frequency plasma heating in the URAGAN-3M torsatron

    International Nuclear Information System (INIS)

    Lysoivan, A.I.; Moiseenko, V.E.; Plyusnin, V.V.; Kasilov, S.V.; Bondarenko, V.N.; Chechkin, V.V.; Fomin, I.P.; Grigor'eva, L.I.; Konovalov, V.G.; Koval'ov, S.V.; Litvinov, A.P.; Mironov, Yu.K.; Nazarov, N.I.; Pavlichenko, O.S.; Pavlichenko, R.O.; Shapoval, A.N.; Skibenko, A.I.; Volkov, E.D.

    1995-01-01

    Numerical and experimental results of Alfven wave heating of plasmas in the frequency range below the ion cyclotron frequency (ω ci ) are presented. Two different types of antenna were used for plasma production and heating: a frame type antenna (FTA) conventionally used in the URAGAN-3M device and a three-half-turn antenna (THTA) proposed recently to avoid the deleterious effects of conversion of fast wave to slow wave in the plasma periphery and to perform plasma core heating more effectively. Numerical modeling of electromagnetic field excitation in the URAGAN-3M plasma by the FTA and THTA was performed using a one-dimensional code. The results of calculations showed better performance of the compact THTA compared with the FTA for the case of a high density plasma (approximately 10 13 cm -3 ). When using the THTA, the experiments performed showed the possibility of dense plasma production (more than 2x10 13 cm -3 ) and heating, which had not been obtained earlier in the URAGAN-3M. Shifting the power deposition profile deeper inside the plasma body with the THTA resulted in modification of the plasma density profile and an improvement in plasma confinement. ((orig.))

  9. Low velocity target detection based on time-frequency image for high frequency ground wave radar

    Institute of Scientific and Technical Information of China (English)

    YAN Songhua; WU Shicai; WEN Biyang

    2007-01-01

    The Doppler spectral broadening resulted from non-stationary movement of target and radio-frequency interference will decrease the veracity of target detection by high frequency ground wave(HEGW)radar.By displaying the change of signal energy on two dimensional time-frequency images based on time-frequency analysis,a new mathematical morphology method to distinguish target from nonlinear time-frequency curves is presented.The analyzed results from the measured data verify that with this new method the target can be detected correctly from wide Doppler spectrum.

  10. Effect of driving voltages in dual capacitively coupled radio frequency plasma: A study by nonlinear global model

    International Nuclear Information System (INIS)

    Bora, B.

    2015-01-01

    On the basis of nonlinear global model, a dual frequency capacitively coupled radio frequency plasma driven by 13.56 MHz and 27.12 MHz has been studied to investigate the influences of driving voltages on the generation of dc self-bias and plasma heating. Fluid equations for the ions inside the plasma sheath have been considered to determine the voltage-charge relations of the plasma sheath. Geometrically symmetric as well as asymmetric cases with finite geometrical asymmetry of 1.2 (ratio of electrodes area) have been considered to make the study more reasonable to experiment. The electrical asymmetry effect (EAE) and finite geometrical asymmetry is found to work differently in controlling the dc self-bias. The amount of EAE has been primarily controlled by the phase angle between the two consecutive harmonics waveforms. The incorporation of the finite geometrical asymmetry in the calculations shift the dc self-bias towards negative polarity direction while increasing the amount of EAE is found to increase the dc self-bias in either direction. For phase angle between the two waveforms ϕ = 0 and ϕ = π/2, the amount of EAE increases significantly with increasing the low frequency voltage, whereas no such increase in the amount of EAE is found with increasing high frequency voltage. In contrast to the geometrically symmetric case, where the variation of the dc self-bias with driving voltages for phase angle ϕ = 0 and π/2 are just opposite in polarity, the variation for the geometrically asymmetric case is different for ϕ = 0 and π/2. In asymmetric case, for ϕ = 0, the dc self-bias increases towards the negative direction with increasing both the low and high frequency voltages, but for the ϕ = π/2, the dc-self bias is increased towards positive direction with increasing low frequency voltage while dc self-bias increases towards negative direction with increasing high frequency voltage

  11. Interferometric measurements of plasma density in highplasmas

    International Nuclear Information System (INIS)

    Quinn, W.E.

    1977-01-01

    The coupled-cavity laser interferometer technique is particularly applicable to the measurement of pulsed plasma densities. This technique is based on the fact that if a small fraction of a gas laser's output radiation is reflected into the laser with an external mirror, the intensity of the laser output is modulated. These amplitude or intensity modulations are produced by changes in the laser gain. A rotating corner mirror or an oscillating mirror can be used to produce a continuous feedback modulation of the interferometer which produces a continuous background fringe pattern. The presence of plasma in the outer cavity causes an additional change which results in a phase shift of the regular period of the background fringe pattern. The integral of the plasma density along the line of sight can be evaluated by comparison of the time history of the fringes obtained with and without plasma

  12. Synthesis of tungsten oxide, silver, and gold nanoparticles by radio frequency plasma in water

    International Nuclear Information System (INIS)

    Hattori, Yoshiaki; Nomura, Shinfuku; Mukasa, Shinobu; Toyota, Hiromichi; Inoue, Toru; Usui, Tomoya

    2013-01-01

    Highlights: •RF plasma in water was used for nanoparticle synthesis. •Nanoparticles were produced from erosion of metallic electrode. •Rectangular and spherical tungsten oxide nanoparticles were produced. •No oxidations of the silver and gold spherical nanoparticles were produced. -- Abstract: A process for synthesis of nanoparticles using plasma in water generated by a radio frequency of 27.12 MHz is proposed. Tungsten oxide, silver, and gold nanoparticles were produced at 20 kPa through erosion of a metallic electrode exposed to plasma. Characterization of the produced nanoparticles was carried out by XRD, absorption spectrum, and TEM. The nanoparticle sizes were compared with those produced by a similar technique using plasma in liquid

  13. Experimental study of the hollow cathode radio-frequency plasma mixture: Argon-Oxygen

    International Nuclear Information System (INIS)

    Saloum, S.; Naddaf, M.

    2008-01-01

    This study presents experimental results of plasma gas mixture Ar-O 2 for different mixing ratios in radio-frequency hollow cathode plasma. The following plasma parameters have been investigated: The electronic temperature, plasma potential, floating potential, emission atomic lines intensities, as a function of some variables, where the effect of power has been studied in the range [100-300 W], and the effect of pressure has been studied in the range [0.05-0.3 mbar]. The effect of relative composition has been studied for a fixed power and pressure. Two diagnostic techniques have been employed: Optical emission spectroscopy and langmuir probe. The most important result of this study is the ability to measure the relative atomic density of oxygen by optical emission spectroscopy, where the maximum of this density is obtained for the mixture 40% Ar - 60% O 2 . (author)

  14. Microwave frequency sweep interferometer for plasma density measurements in ECR ion sources: Design and preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Torrisi, Giuseppe [INFN - Laboratori Nazionali del Sud, Via S. Sofia 62, 95125 Catania (Italy); University Mediterranea of Reggio Calabria, Reggio Calabria (Italy); Mascali, David; Neri, Lorenzo; Leonardi, Ornella; Celona, Luigi; Castro, Giuseppe; Agnello, Riccardo; Caruso, Antonio; Passarello, Santi; Longhitano, Alberto; Gammino, Santo [INFN - Laboratori Nazionali del Sud, Via S. Sofia 62, 95125 Catania (Italy); Sorbello, Gino [INFN - Laboratori Nazionali del Sud, Via S. Sofia 62, 95125 Catania (Italy); University of Catania, Catania, Italy and INFN-LNS, Catania (Italy); Isernia, Tommaso [University Mediterranea of Reggio Calabria, Reggio Calabria (Italy)

    2016-02-15

    The Electron Cyclotron Resonance Ion Sources (ECRISs) development is strictly related to the availability of new diagnostic tools, as the existing ones are not adequate to such compact machines and to their plasma characteristics. Microwave interferometry is a non-invasive method for plasma diagnostics and represents the best candidate for plasma density measurement in hostile environment. Interferometry in ECRISs is a challenging task mainly due to their compact size. The typical density of ECR plasmas is in the range 10{sup 11}–10{sup 13} cm{sup −3} and it needs a probing beam wavelength of the order of few centimetres, comparable to the chamber radius. The paper describes the design of a microwave interferometer developed at the LNS-INFN laboratories based on the so-called “frequency sweep” method to filter out the multipath contribution in the detected signals. The measurement technique and the preliminary results (calibration) obtained during the experimental tests will be presented.

  15. High-frequency homogenization of zero frequency stop band photonic and phononic crystals

    CERN Document Server

    Antonakakis, Tryfon; Guenneau, Sebastien

    2013-01-01

    We present an accurate methodology for representing the physics of waves, for periodic structures, through effective properties for a replacement bulk medium: This is valid even for media with zero frequency stop-bands and where high frequency phenomena dominate. Since the work of Lord Rayleigh in 1892, low frequency (or quasi-static) behaviour has been neatly encapsulated in effective anisotropic media. However such classical homogenization theories break down in the high-frequency or stop band regime. Higher frequency phenomena are of significant importance in photonics (transverse magnetic waves propagating in infinite conducting parallel fibers), phononics (anti-plane shear waves propagating in isotropic elastic materials with inclusions), and platonics (flexural waves propagating in thin-elastic plates with holes). Fortunately, the recently proposed high-frequency homogenization (HFH) theory is only constrained by the knowledge of standing waves in order to asymptotically reconstruct dispersion curves an...

  16. High Frequency Acoustic Propagation using Level Set Methods

    Science.gov (United States)

    2007-01-01

    solution of the high frequency approximation to the wave equation. Traditional solutions to the Eikonal equation in high frequency acoustics are...the Eikonal equation derived from the high frequency approximation to the wave equation, ucuH ∇±=∇ )(),( xx , with the nonnegative function c(x...For simplicity, we only consider the case ucuH ∇+=∇ )(),( xx . Two difficulties must be addressed when solving the Eikonal equation in a fixed

  17. New features of current-driven low-frequency instabilities in a Q-machine plasma

    International Nuclear Information System (INIS)

    Dimitriu, Dan-Gheorghe; Ignatescu, Valerian; Lozneanu, Erzilia; Sanduloviciu, Mircea; Ionita, Codrina; Schrittwieser, Roman Wolfgang

    2001-01-01

    Among the instabilities in a low-density magnetized plasma column, the electrostatic ion-cyclotron instability (EICI) and the potential relaxation instability (PRI) are the best known and most thoroughly investigated. Both instabilities are excited by drawing an electron current parallel to the magnetic field towards a circular collector (CO), which is inserted into the plasma column perpendicular to the axis. For the PRI, the radius of CO must be considerably larger than the ion gyroradius so that the ion trajectories can be approximated as one-dimensional. For the EICI, the radius of CO must be considerably smaller than that of the plasma column, but also larger than one ion gyroradius. A transition from the PRI into the EICI was reported earlier. A certain range of CO radii was found where both instabilities could be excited simultaneously. We report on a strong modulation of the EICI by the PRI, obtained for gradually increasing the CO bias, with the EICI appearing at first, and later the PRI. The EICI frequency was about four times larger than that of the PRI. The modulation not only affects the amplitude but also the frequency of the EICI. This leads to the formation of sidebands in the spectrum around f EICI with a frequency difference equal to ± f PRI . In addition, we find that the EICI frequency depends not only on the magnetic field strength but also on the CO current. Our data also show a strong non-linear dependence of the PRI frequency on the magnetic field strength. To explain these features, we propose a new phenomenological model, which is able to clarify the role of complex space charge configurations for low frequency instabilities in a low-density magnetized plasma column. (authors)

  18. Multichannel euv spectroscopy of high temperature plasmas

    International Nuclear Information System (INIS)

    Fonck, R.J.

    1983-11-01

    Spectroscopy of magnetically confined high temperature plasmas in the visible through x-ray spectral ranges deals primarily with the study of impurity line radiation or continuum radiation. Detailed knowledge of absolute intensities, temporal behavior, and spatial distributions of the emitted radiation is desired. As tokamak facilities become more complex, larger, and less accessible, there has been an increased emphasis on developing new instrumentation to provide such information in a minimum number of discharges. The availability of spatially-imaging detectors for use in the vacuum ultraviolet region (especially the intensified photodiode array) has generated the development of a variety of multichannel spectrometers for applications on tokamak facilities

  19. Study of ultrasound-assisted radio-frequency plasma discharges in n-dodecane

    Science.gov (United States)

    Camerotto, Elisabeth; De Schepper, Peter; Nikiforov, Anton Y.; Brems, Steven; Shamiryan, Denis; Boullart, Werner; Leys, Christophe; De Gendt, Stefan

    2012-10-01

    This paper investigates the generation of a stable plasma phase in a liquid hydrocarbon (n-dodecane) by means of ultrasound (US) and radio-frequency (RF) or electromagnetic radiation. It is demonstrated for the first time that ultrasonic aided RF plasma discharges can be generated in a liquid. Plasma discharges are obtained for different gas mixtures at a pressure of 12 kPa and at low ignition powers (100 W for RF and 2.4 W cm-2 for US). Direct carbon deposition from the liquid precursor on Cu, Ni, SiO2 and Si substrates has been obtained and no apparent compositional or structural difference among the substrate materials was observed. Characterization of the deposited solid phase revealed an amorphous structure. In addition, structural changes in the liquid precursor after plasma treatment have been analysed. Optical emission spectroscopy (OES) allowed the estimation of several plasma characteristic temperatures. The plasma excitation temperature was estimated to be about 2.3-2.4 eV. The rotational and vibrational temperatures of the discharge in n-dodecane with Ar as a feed gas were 1400 K and 6500 K, respectively. In Ar/O2 plasma, an increased rotational (1630 K) and vibrational temperature (7200 K) were obtained.

  20. Anion dynamics in the first 10 milliseconds of an argon-acetylene radio-frequency plasma

    International Nuclear Information System (INIS)

    Van de Wetering, F M J H; Beckers, J; Kroesen, G M W

    2012-01-01

    The time evolution of the smallest anions (C 2 H - and H 2 CC - ), just after plasma ignition, is studied by means of microwave cavity resonance spectroscopy (MCRS) in concert with laser-induced photodetachment under varying gas pressure and temperature in an argon-acetylene radio-frequency (13.56 MHz) plasma. These anions act as an initiator for spontaneous dust particle formation in these plasmas. With an intense 355 nm Nd:YAG laser pulse directed through the discharge, electrons are detached only from these anions present in the laser path. This results in a sudden increase in the electron density in the plasma, which can accurately and with sub-microsecond time resolution be measured with MCRS. By adjusting the time after plasma ignition at which the laser is fired through the discharge, the time evolution of the anion density can be studied. We have operated in the linear regime: the photodetachment signal is proportional to the laser intensity. This allowed us to study the trends of the photodetachment signal as a function of the operational parameters of the plasma. The density of the smallest anions steadily increases in the first few milliseconds after plasma ignition, after which it reaches a steady state. While keeping the gas density constant, increasing the gas temperature in the range 30-120 °C limits the number of smallest anions and saturates at a temperature of about 90 °C. A reaction pathway is proposed to explain the observed trends.

  1. Device for plasma confinement and heating by high currents and nonclassical plasma transport properties

    Science.gov (United States)

    Coppi, B.; Montgomery, D.B.

    1973-12-11

    A toroidal plasma containment device having means for inducing high total plasma currents and current densities and at the same time emhanced plasma heating, strong magnetic confinement, high energy density containment, magnetic modulation, microwaveinduced heating, and diagnostic accessibility is described. (Official Gazette)

  2. A plasma microlens for ultrashort high power lasers

    Science.gov (United States)

    Katzir, Yiftach; Eisenmann, Shmuel; Ferber, Yair; Zigler, Arie; Hubbard, Richard F.

    2009-07-01

    We present a technique for generation of miniature plasma lens system that can be used for focusing and collimating a high intensity femtosecond laser pulse. The plasma lens was created by a nanosecond laser, which ablated a capillary entrance. The spatial configuration of the ablated plasma focused a high intensity femtosecond laser pulse. This configuration offers versatility in the plasma lens small f-number for extremely tight focusing of high power lasers with no damage threshold restrictions of regular optical components.

  3. A plasma microlens for ultrashort high power lasers

    International Nuclear Information System (INIS)

    Katzir, Yiftach; Eisenmann, Shmuel; Ferber, Yair; Zigler, Arie; Hubbard, Richard F.

    2009-01-01

    We present a technique for generation of miniature plasma lens system that can be used for focusing and collimating a high intensity femtosecond laser pulse. The plasma lens was created by a nanosecond laser, which ablated a capillary entrance. The spatial configuration of the ablated plasma focused a high intensity femtosecond laser pulse. This configuration offers versatility in the plasma lens small f-number for extremely tight focusing of high power lasers with no damage threshold restrictions of regular optical components.

  4. Numerical studies of independent control of electron density and gas temperature via nonlinear coupling in dual-frequency atmospheric pressure dielectric barrier discharge plasmas

    International Nuclear Information System (INIS)

    Zhang, Z. L.; Nie, Q. Y.; Wang, Z. B.; Gao, X. T.; Kong, F. R.; Sun, Y. F.; Jiang, B. H.

    2016-01-01

    Dielectric barrier discharges (DBDs) provide a promising technology of generating non-equilibrium cold plasmas in atmospheric pressure gases. For both application-focused and fundamental studies, it is important to explore the strategy and the mechanism for enabling effective independent tuning of key plasma parameters in a DBD system. In this paper, we report numerical studies of effects of dual-frequency excitation on atmospheric DBDs, and modulation as well as separate tuning mechanism, with emphasis on dual-frequency coupling to the key plasma parameters and discharge evolution. With an appropriately applied low frequency to the original high frequency, the numerical calculation demonstrates that a strong nonlinear coupling between two frequencies governs the process of ionization and energy deposition into plasma, and thus raises the electron density significantly (e.g., three times in this case) in comparisons with a single frequency driven DBD system. Nevertheless, the gas temperature, which is mainly determined by the high frequency discharge, barely changes. This method then enables a possible approach of controlling both averaged electron density and gas temperature independently.

  5. Calibration of High Frequency MEMS Microphones

    Science.gov (United States)

    Shams, Qamar A.; Humphreys, William M.; Bartram, Scott M.; Zuckewar, Allan J.

    2007-01-01

    Understanding and controlling aircraft noise is one of the major research topics of the NASA Fundamental Aeronautics Program. One of the measurement technologies used to acquire noise data is the microphone directional array (DA). Traditional direction array hardware, consisting of commercially available condenser microphones and preamplifiers can be too expensive and their installation in hard-walled wind tunnel test sections too complicated. An emerging micro-machining technology coupled with the latest cutting edge technologies for smaller and faster systems have opened the way for development of MEMS microphones. The MEMS microphone devices are available in the market but suffer from certain important shortcomings. Based on early experiments with array prototypes, it has been found that both the bandwidth and the sound pressure level dynamic range of the microphones should be increased significantly to improve the performance and flexibility of the overall array. Thus, in collaboration with an outside MEMS design vendor, NASA Langley modified commercially available MEMS microphone as shown in Figure 1 to meet the new requirements. Coupled with the design of the enhanced MEMS microphones was the development of a new calibration method for simultaneously obtaining the sensitivity and phase response of the devices over their entire broadband frequency range. Over the years, several methods have been used for microphone calibration. Some of the common methods of microphone calibration are Coupler (Reciprocity, Substitution, and Simultaneous), Pistonphone, Electrostatic actuator, and Free-field calibration (Reciprocity, Substitution, and Simultaneous). Traditionally, electrostatic actuators (EA) have been used to characterize air-condenser microphones for wideband frequency ranges; however, MEMS microphones are not adaptable to the EA method due to their construction and very small diaphragm size. Hence a substitution-based, free-field method was developed to

  6. 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

  7. Frequency spectral broadening of lower hybrid waves in tokamak plasmas - causes and effects

    Energy Technology Data Exchange (ETDEWEB)

    Pericoli Ridolfini, V; Giannone, L.; Bartiromo, R [Associazione Euratom-ENEA sulla Fusione, Rome (Italy). Centro Ricerche Energia Frascati

    1994-04-01

    The frequency spectral broadening of lower hybrid (LH) waves injected into tokamak plasmas is extensively analyzed with reference mostly to experimental data from the ASDEX tokamak. The link between the magnitude of the pump spectral width and the degradation of the LH current drive efficiency (up to a factor of 2), pointed out in previous works, is explained. The experimental behaviour of LH power absorption is also well reproduced, even in situations when the access of the launched LH waves to the core plasma should be largely forbidden. Experiments are described that are aimed at determined whether parametric decay instabilities (PDIs) or scattering of LH waves by density fluctuations in the plasma edge are causes of the broadening of the LH pump frequency spectrum. Fluctuations emerge as the largely dominant process, while no signature of PDI processes is observed. Careful measurements of the density fluctuations in the ASDEX scrape-off layer plasma allow the analytical description given by Andrews and Perkins to be assumed as the appropriate model of LH scattering. Indeed, it supplies the correct magnitude for the frequency spectral width of the LH pump, and explains quantitatively, together with a ray tracing code, why the CD efficiency decreases with the broadening of the pump spectrum. It can also account for the observed LH power absorption coefficient. (author). 48 refs, 13 figs, 2 tabs.

  8. Cosmic microwave background distortions at high frequencies

    International Nuclear Information System (INIS)

    Peter, W.; Peratt, A.L.

    1988-01-01

    The authors analyze the deviation of the cosmic background radiation spectrum from the 2.76+-0.02 0 Κ blackbody curve. If the cosmic background radiation is due to absorption and re-emission of synchrotron radiation from galactic-width current filaments, higher-order synchrotron modes are less thermalized than lower-order modes, causing a distortion of the blackbody curve at higher frequencies. New observations of the microwave background spectrum at short wavelengths should provide an indication of the number of synchrotron modes thermalized in this process. The deviation of the spectrum from that of a perfect blackbody can thus be correlated with astronomical observations such as filament temperatures and electron energies. The results are discussed and compared with the theoretical predictions of other models which assume the presence of intergalactic superconducting cosmic strings

  9. Frequency domain and wavelet analysis of the laser-induced plasma shock waves

    Energy Technology Data Exchange (ETDEWEB)

    Burger, Miloš, E-mail: milosb@ff.bg.ac.rs; Nikolić, Zoran

    2015-08-01

    In addition to optical emission, another trace of interest that laser-induced plasma provides is a form of acoustic feedback. The acoustic emission (AE) signals were obtained using both microphone and piezo transducers. This kind of optoacoustic signals have some distinct features resembling the short, burst-like sounds, that may differ significantly depending mainly on the sample exposed and irradiance applied. Experiments were performed on atmospheric pressure by irradiating various metallic samples. The recorded waveforms were examined and numerically processed. Single-shot acoustical spectra have shown significant potential of providing valuable supplementary information regarding plasma propagation dynamics. Moreover, the general approach suggests the possibility of making the whole measurement system cost-effective and portable. - Highlights: • We report acoustical waveform, and acoustical spectroscopy measurements and analysis in a laser-induced plasma of a different metals in air. • Both piezo and microphone transducer were used. • The acoustical spectra of the emission were obtained when the sample (and plasma) were enclosed in experimental chamber. • The acquired acoustical spectra are time-integrated and the frequency peaks were sharp and relatively isolated. • Finally, both time and frequency resolved wavelet spectrogram present a novel method of observing laser-induced plasma behavior.

  10. Radial variation of refractive index, plasma frequency and phase velocity in laser induced air plasma

    CSIR Research Space (South Africa)

    Mathuthu, M

    2006-12-01

    Full Text Available is the concentration of the emitting species, is the transition probability, is the emitted wavelength of the detected line, is the statistical weight of the upper level of the transition, is the excitation energy, is the Boltzmann constant, and is the partition... the Boltzmann plane: (3) For each species in a sample, the slope gives the plasma tem- perature while the intercept gives the sample concentration. B. Density Measurement The collisional processes between atoms and ions affect the shape and width...

  11. Plasma phospholipid pentadecanoic acid, EPA, and DHA, and the frequency of dairy and fish product intake in young children

    Directory of Open Access Journals (Sweden)

    Nicolai A. Lund-Blix

    2016-08-01

    Full Text Available Background: There is a lack of studies comparing dietary assessment methods with the biomarkers of fatty acids in children. Objective: The objective was to evaluate the suitability of a food frequency questionnaire (FFQ to rank young children according to their intake of dairy and fish products by comparing food frequency estimates to the plasma phospholipid fatty acids pentadecanoic acid, eicosapentaenoic acid (EPA, and docosahexaenoic acid (DHA. Design: Cross-sectional data for the present study were derived from the prospective cohort ‘Environmental Triggers of Type 1 Diabetes Study’. Infants were recruited from the Norwegian general population during 2001–2007. One hundred and ten (age 3–10 years children had sufficient volumes of plasma and FFQ filled in within 2 months from blood sampling and were included in this evaluation study. The quantitative determination of plasma phospholipid fatty acids was done by fatty acid methyl ester analysis. The association between the frequency of dairy and fish product intake and the plasma phospholipid fatty acids was assessed by a Spearman correlation analysis and by investigating whether participants were classified into the same quartiles of distribution. Results: Significant correlations were found between pentadecanoic acid and the intake frequency of total dairy products (r=0.29, total fat dairy products (r=0.39, and cheese products (r=0.36. EPA and DHA were significantly correlated with the intake frequency of oily fish (r=0.26 and 0.37, respectively and cod liver/fish oil supplements (r=0.47 for EPA and r=0.50 DHA. To a large extent, the FFQ was able to classify individuals into the same quartile as the relevant fatty acid biomarker. Conclusions: The present study suggests that, when using the plasma phospholipid fatty acids pentadecanoic acid, EPA, and DHA as biomarkers, the FFQ used in young children showed a moderate capability to rank the intake frequency of dairy products with a

  12. Emission spectroscopy of highly ionized high-temperature plasma jets

    Energy Technology Data Exchange (ETDEWEB)

    Belevtsev, A A; Chinnov, V F; Isakaev, E Kh [Associated Institute for High Temperatures, Russian Academy of Sciences Izhorskaya 13/19, Moscow, 125412 (Russian Federation)

    2006-08-01

    This paper deals with advanced studies on the optical emission spectroscopy of atmospheric pressure highly ionized high-temperature argon and nitrogen plasma jets generated by a powerful arc plasmatron. The emission spectra are taken in the 200-1000 nm range with a spectral resolution of {approx}0.01-0.02 nm. The exposure times are 6 x 10{sup -6}-2 x 10{sup -2} s, the spatial resolution is 0.02-0.03 mm. The recorded jet spectra are abundant in spectral lines originating from different ionization stages. In nitrogen plasmas, tens of vibronic bands are also observed. To interpret and process these spectra such that plasma characteristics can be derived, a purpose-developed automated processing system is applied. The use of a CCD camera at the spectrograph output allows a simultaneous recording of the spectral and chord intensity distributions of spectral lines, which can yet belong to the overlapped spectra of the first and second orders of interference. The modern optical diagnostic means and methods used permit the determination of spatial distributions of electron number densities and temperatures and evaluation of rotational temperatures. The radial profiles of the irradiating plasma components can also be obtained. Special attention is given to the method of deriving rotational temperatures using vibronic bands with an incompletely identified rotational structure.

  13. Plasmas in saline solutions sustained using rectified ac voltages: polarity and frequency effects on the discharge behaviour

    International Nuclear Information System (INIS)

    Chang Hungwen; Hsu Chengche

    2012-01-01

    In this work, three major problems, namely severe electrode damage, poor plasma stability and excess power consumption, arising in ac-driven plasmas in saline solutions are solved using a rectified power source. Diagnostic studies on the effects of power source polarity and frequency on the plasma behaviour are performed. Examination of I-V characteristics and temporally resolved light emission shows that the polarity significantly influences the current amplitude when the plasma exists, while the frequency alters the bubble dynamics, which in turn affects the plasma ignition voltage. When the plasma is driven by a rectified ac power source, the electrode erosion is reduced substantially. With a low frequency, moderate applied voltage and positively rectified ac power source (e.g. 100 Hz and 350 V), a stable plasma is ignited in nearly every power cycle. (paper)

  14. Potential formation and confinement in high density plasma on the GAMMA 10 tandem mirror

    International Nuclear Information System (INIS)

    Yatsu, K.

    2002-01-01

    After the attainment of doubling of the density due to the potential confinement, GAMMA 10 experiments have been directed to realization of a high density plasma and also to study dependence of the confining potential and confinement time on the plasma density. These problems are important to understand the physics of potential formation in tandem mirrors and also for the development of a tandem mirror reactor. We reported high density plasma production by using an ion cyclotron range of frequency heating at a high harmonic frequency in the last IAEA Conference. However, the diamagnetic signal of the high density plasma decreased when electron cyclotron resonance heating (ECRH) was applied due to some instabilities. Recently, the high density plasma production was much improved by adjusting the spacing of the conducting plates installed in the anchor transition regions, which enabled us to produce a high density plasma without degradation of the diamagnetic signal with ECRH and also to study the density dependence. In this paper we report production of a high density plasma and dependence of the confining potential and the confinement time on the density. (author)

  15. Power supply and impedance matching to drive technological radio-frequency plasmas with customized voltage waveforms.

    Science.gov (United States)

    Franek, James; Brandt, Steven; Berger, Birk; Liese, Martin; Barthel, Matthias; Schüngel, Edmund; Schulze, Julian

    2015-05-01

    We present a novel radio-frequency (RF) power supply and impedance matching to drive technological plasmas with customized voltage waveforms. It is based on a system of phase-locked RF generators that output single frequency voltage waveforms corresponding to multiple consecutive harmonics of a fundamental frequency. These signals are matched individually and combined to drive a RF plasma. Electrical filters are used to prevent parasitic interactions between the matching branches. By adjusting the harmonics' phases and voltage amplitudes individually, any voltage waveform can be approximated as a customized finite Fourier series. This RF supply system is easily adaptable to any technological plasma for industrial applications and allows the commercial utilization of process optimization based on voltage waveform tailoring for the first time. Here, this system is tested on a capacitive discharge based on three consecutive harmonics of 13.56 MHz. According to the Electrical Asymmetry Effect, tuning the phases between the applied harmonics results in an electrical control of the DC self-bias and the mean ion energy at almost constant ion flux. A comparison with the reference case of an electrically asymmetric dual-frequency discharge reveals that the control range of the mean ion energy can be significantly enlarged by using more than two consecutive harmonics.

  16. Transmission line theory for long plasma production by radio frequency discharges between parallel-plate electrodes

    International Nuclear Information System (INIS)

    Nonaka, S.

    1991-01-01

    In order to seek for a radio frequency (RF) eigen-mode of waves in producing a plasma between a pair of long dielectric-covered parallel-plate RF electrodes, this paper analyzed all normal modes propagating along the electrodes by solving Maxwell's equations. The result showed that only an odd surface wave mode will produce the plasma in usual experimental conditions, which will become a basic transmission line theory when use of such long electrodes for on-line mass-production of amorphous silicon solar cells

  17. A simple microwave technique for plasma density measurement using frequency modulation

    International Nuclear Information System (INIS)

    Bora, D.; Jayakumar, R.; Vijayashankar, M.K.

    1984-01-01

    A simple method of determining the phase variation unambiguously during microwave interferometric measurement is described. The frequency of the Klystron source is modulated with the help of staircase voltage pulse. The height of each stair is adjusted such that the corresponding phase shift in the test branch with an additional path length is 90 0 . Signals, proportional to cosine and sine of the phase shift due to plasma, can be generated in the same channel and plasma density information can be inferred. The microwave hardware remains the same as in conventional interferometry and the cost of such a scheme is low. (author)

  18. High frequency response of open quantum dots

    International Nuclear Information System (INIS)

    Brunner, R.; Meisels, R.; Kuchar, F.; Ferry, D.; Elhassan, M.; Ishibashi, K.

    2002-01-01

    Full text: We investigate the response of the transport through open quantum dots to millimeterwave radiation (up to 55 GHz). In the low-field region ( 11 cm -2 and a mobility of 1.2 10 6 cm 2 /Vs. By applying a sufficiently negative voltage to the gates the 2DES is split into two regions connected only by a dot-like region (about 350 nm diameter) between them. The DC data exhibit backscattering peaks at fields of a few tenth of a Tesla. Shubnikovde- Haas (SdH) oscillations appear above 0.5 T. While the SdH oscillations show the usual temperature dependence, the backscattering peaks are temperature independent up to 2.5 K. The backscattering peak shows a reduction of 10 percent due to the millimeterwave irradiation. However, due to the temperature independence of this peak, this reduction cannot simply be attributed to electron heating. This conclusion is supported by the observation of a strong frequency dependence of the reduction of the peak height. (author)

  19. Gender Identification Using High-Frequency Speech Energy: Effects of Increasing the Low-Frequency Limit.

    Science.gov (United States)

    Donai, Jeremy J; Halbritter, Rachel M

    The purpose of this study was to investigate the ability of normal-hearing listeners to use high-frequency energy for gender identification from naturally produced speech signals. Two experiments were conducted using a repeated-measures design. Experiment 1 investigated the effects of increasing high-pass filter cutoff (i.e., increasing the low-frequency spectral limit) on gender identification from naturally produced vowel segments. Experiment 2 studied the effects of increasing high-pass filter cutoff on gender identification from naturally produced sentences. Confidence ratings for the gender identification task were also obtained for both experiments. Listeners in experiment 1 were capable of extracting talker gender information at levels significantly above chance from vowel segments high-pass filtered up to 8.5 kHz. Listeners in experiment 2 also performed above chance on the gender identification task from sentences high-pass filtered up to 12 kHz. Cumulatively, the results of both experiments provide evidence that normal-hearing listeners can utilize information from the very high-frequency region (above 4 to 5 kHz) of the speech signal for talker gender identification. These findings are at variance with current assumptions regarding the perceptual information regarding talker gender within this frequency region. The current results also corroborate and extend previous studies of the use of high-frequency speech energy for perceptual tasks. These findings have potential implications for the study of information contained within the high-frequency region of the speech spectrum and the role this region may play in navigating the auditory scene, particularly when the low-frequency portion of the spectrum is masked by environmental noise sources or for listeners with substantial hearing loss in the low-frequency region and better hearing sensitivity in the high-frequency region (i.e., reverse slope hearing loss).

  20. Research on the FDTD method of scattering effects of obliquely incident electromagnetic waves in time-varying plasma sheath on collision and plasma frequencies

    Science.gov (United States)

    Chen, Wei; Guo, Li-xin; Li, Jiang-ting

    2017-04-01

    This study analyzes the scattering characteristics of obliquely incident electromagnetic (EM) waves in a time-varying plasma sheath. The finite-difference time-domain algorithm is applied. According to the empirical formula of the collision frequency in a plasma sheath, the plasma frequency, temperature, and pressure are assumed to vary with time in the form of exponential rise. Some scattering problems of EM waves are discussed by calculating the radar cross section (RCS) of the time-varying plasma. The laws of the RCS varying with time are summarized at the L and S wave bands.

  1. High density turbulent plasma processes from a shock tube

    International Nuclear Information System (INIS)

    Oyedeji, O.; Johnson, J.A. III

    1991-01-01

    We have finished the first stages of our experimental and theoretical investigations on models for energy and momentum transport and for photon-particle collision processes in a turbulent quasi-stationary high density plasma. The system is explored by beginning to determine the turbulence phenomenology associated with an ionizing shock wave. The theoretical underpinnings are explored for phonon particle collisions by determining the collisional redistribution function, using Lioville Space Green's Function, which will characterize the inelastic scattering of the radiation from one frequency to another. We have observed that a weak magnetic field tends to increase the apparent random-like behaviors in a collisional turbulent plasma. On the theoretical side, we have been able to achieve a form for the collisional redistribution function. It remains to apply these concepts to a stationary turbulent plasma in the reflected ionizing shock wave and to exercise the implications of evaluations of the collisional redistribution function for such a system when it is probed by a strong radiation source. These results are discussed in detail in the publications, which have resulted from the this effort, cited at the end of the report

  2. Low-frequency instabilities of a warm plasma in a magnetic field

    International Nuclear Information System (INIS)

    Smith, D.F.; Hollweg, J.V.

    1977-01-01

    The marginal stability of a plasma carrying current along the static magnetic field with isotropic Maxwellian ions and isotropic Maxwellian electrons drifting relative to the ions is investigated. The complete electromagnetic dispersion relation is studied using numerical techniques; the electron sums are restricted to three terms which limits the analysis to frequencies much less than the electron gyro-frequency, but includes frequencies somewhat above the ion gyro-frequency. A 'kink-like' instability and an instability of the Alfven mode are found to have the lowest threshold drift velocities in most cases. In fact the threshold drift for the kink-like instability can be significantly less than the ion thermal speed. Electrostatic and electromagnetic ion-cyclotron instabilities are also found as well as the electro-static ion-acoustic instability. No instability of the fast magnetosonic mode was found. The stability analysis provides only threshold drift velocities and gives no information about growth rates. (author)

  3. A high-switching-frequency flyback converter in resonant mode

    NARCIS (Netherlands)

    Li, Jianting; van Horck, Frank B.M.; Daniel, Bobby J.; Bergveld, Henk Jan

    2017-01-01

    The demand of miniaturization of power systems has accelerated the research on high-switching-frequency power converters. A flyback converter in resonant mode that features low switching losses, less transformer losses, and low switching noise at high switching frequency is investigated in this

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    The advent of the plasma revolution began in the 1970's with the exploitation of plasma sources for anisotropic etching and processing of materials. In recent years, plasma processing has gained popularity, with research institutions adopting projects in the field and industries implementing dry processing in their production lines. The advantages of utilizing plasma sources would be uniform processing over a large exposed surface area, and the reduction of toxic emissions. This leads to reduced costs borne by manufacturers which could be passed down as consumer savings, and a reduction in negative environmental impacts. Yet, one constraint that plagues the industry would be the control of contaminants in a plasma reactor which becomes evident when reactions are conducted in a clean vacuum environment. In this work, amorphous silicon (a-Si) thin films were grown on glass substrates in a low frequency inductively coupled plasma (LF-ICP) reactor with a top lid made of quartz. Even though the chamber was kept at high vacuum (~10 −4 Pa), it was evident through secondary ion mass spectroscopy (SIMS) and Fourier-transform infra-red spectroscopy (FTIR) that oxygen contaminants were present. With the aid of optical emission spectroscopy (OES) the contaminant species were identified. The design of the LF-ICP reactor was then modified to incorporate an Alumina (Al 2 O 3 ) lid. Results indicate that there were reduced amounts of contaminants present in the reactor, and that an added benefit of increased power transfer to the plasma, improving deposition rate of thin films was realized. The results of this study is conclusive in showing that Al 2 O 3 is a good alternative as a top-lid of an LF-ICP reactor, and offers industries a solution in improving quality and rate of growth of thin films. (author)

  5. 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...

  6. Nanohertz frequency determination for the gravity probe B high frequency superconducting quantum interference device signal.

    Science.gov (United States)

    Salomon, M; Conklin, J W; Kozaczuk, J; Berberian, J E; Keiser, G M; Silbergleit, A S; Worden, P; Santiago, D I

    2011-12-01

    In this paper, we present a method to measure the frequency and the frequency change rate of a digital signal. This method consists of three consecutive algorithms: frequency interpolation, phase differencing, and a third algorithm specifically designed and tested by the authors. The succession of these three algorithms allowed a 5 parts in 10(10) resolution in frequency determination. The algorithm developed by the authors can be applied to a sampled scalar signal such that a model linking the harmonics of its main frequency to the underlying physical phenomenon is available. This method was developed in the framework of the gravity probe B (GP-B) mission. It was applied to the high frequency (HF) component of GP-B's superconducting quantum interference device signal, whose main frequency f(z) is close to the spin frequency of the gyroscopes used in the experiment. A 30 nHz resolution in signal frequency and a 0.1 pHz/s resolution in its decay rate were achieved out of a succession of 1.86 s-long stretches of signal sampled at 2200 Hz. This paper describes the underlying theory of the frequency measurement method as well as its application to GP-B's HF science signal.

  7. The effect of dust charge inhomogeneity on low-frequency modes in a strongly coupled plasma

    International Nuclear Information System (INIS)

    Farid, T.; Mamun, A.A.; Shukla, P.K.

    2000-01-01

    An analysis of low-frequency modes accounting for dust grain charge fluctuation and equilibrium grain charge inhomogeneity in a strongly coupled dusty plasma is presented. The existence of an extremely low frequency mode, which is due to the inhomogeneity in the equilibrium dust grain charge, is reported. Besides, the equilibrium dust grain charge inhomogeneity makes the dust-acoustic mode unstable. The strong correlations in the dust fluid significantly drive a new mode as well as the existing dust-acoustic mode. The applications of these results to recent experimental and to some space and astrophysical situations are discussed

  8. Shell structure in superdeformed nuclei at high rotational frequencies

    International Nuclear Information System (INIS)

    Ploszajczak, M.

    1980-01-01

    Properties of the shell structure in superdeformed nuclei at high rotational frequencies are discussed. Moreover, stability of the high spin compound nucleus with respect to the fission and the emission of light particles is investigated. (author)

  9. Dispersive properties and attraction instability of low-frequency collective modes in dusty plasmas

    International Nuclear Information System (INIS)

    Tsytovich, V.N.; Rezendes, D.

    1998-01-01

    A dispersion relation for low-frequency collective modes in dusty plasmas is derived with allowance for attractive and repulsive forces arising between the dust grains due to dissipative fluxes of plasma particles onto the grain surfaces. It is shown that these fluxes give rise to dust attraction instabilities, which are similar to the gravitational instability. In the range of wave numbers corresponding to the stability domain, two types of dust sound waves arise, depending on whether the wavelengths of the collective modes are longer or shorter than the mean free path of the plasma particles (i.e., the distance they travel before they collide with dust grains). The dispersion relation derived is valid for any ratio between the wavelength of the perturbations and the mean free path and encompasses the entire range of intermediate wave numbers. The critical wave numbers that determine the threshold for the onset of attraction instability, which is similar to the Jeans instability, can, in particular, lie within this range. The thresholds for attraction instability and the instability growth rates are obtained numerically for a wide range of the plasma parameters (such as the ratio of the ion temperature to the electron temperature) that are of interest for present-day experiments with dust crystals, plasma etching, and space plasma studies. Computer simulation shows that, in the nonlinear stage, the attraction instability causes the dust cloud to collapse, which leads to the formation of dust plasma crystals. Our investigation makes it possible to trace the processes in the initial stage of dust crystallization. Results are obtained for hydrogen and silicon plasmas, which are most typical of laboratory experiments

  10. Low-frequency, self-sustained oscillations in inductively coupled plasmas used for optical pumping

    Energy Technology Data Exchange (ETDEWEB)

    Coffer, J.; Encalada, N.; Huang, M.; Camparo, J. [Physical Sciences Laboratories, The Aerospace Corporation 2310, E. El Segundo Blvd., El Segundo, California 90245 (United States)

    2014-10-28

    We have investigated very low frequency, on the order of one hertz, self-pulsing in alkali-metal inductively-coupled plasmas (i.e., rf-discharge lamps). This self-pulsing has the potential to significantly vary signal-to-noise ratios and (via the ac-Stark shift) resonant frequencies in optically pumped atomic clocks and magnetometers (e.g., the atomic clocks now flying on GPS and Galileo global navigation system satellites). The phenomenon arises from a nonlinear interaction between the atomic physics of radiation trapping and the plasma's electrical nature. To explain the effect, we have developed an evaporation/condensation theory (EC theory) of the self-pulsing phenomenon.

  11. A MEMS-based high frequency x-ray chopper

    Energy Technology Data Exchange (ETDEWEB)

    Siria, A; Schwartz, W; Chevrier, J [Institut Neel, CNRS-Universite Joseph Fourier Grenoble, BP 166, F-38042 Grenoble Cedex 9 (France); Dhez, O; Comin, F [ESRF, 6 rue Jules Horowitz, F-38043 Grenoble Cedex 9 (France); Torricelli, G [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)

    2009-04-29

    Time-resolved x-ray experiments require intensity modulation at high frequencies (advanced rotating choppers have nowadays reached the kHz range). We here demonstrate that a silicon microlever oscillating at 13 kHz with nanometric amplitude can be used as a high frequency x-ray chopper. We claim that using micro-and nanoelectromechanical systems (MEMS and NEMS), it will be possible to achieve higher frequencies in excess of hundreds of megahertz. Working at such a frequency can open a wealth of possibilities in chemistry, biology and physics time-resolved experiments.

  12. High-order harmonic generation in laser plasma plumes

    CERN Document Server

    Ganeev, Rashid A

    2013-01-01

    This book represents the first comprehensive treatment of high-order harmonic generation in laser-produced plumes, covering the principles, past and present experimental status and important applications. It shows how this method of frequency conversion of laser radiation towards the extreme ultraviolet range matured over the course of multiple studies and demonstrated new approaches in the generation of strong coherent short-wavelength radiation for various applications. Significant discoveries and pioneering contributions of researchers in this field carried out in various laser scientific centers worldwide are included in this first attempt to describe the important findings in this area of nonlinear spectroscopy. "High-Order Harmonic Generation in Laser Plasma Plumes" is a self-contained and unified review of the most recent achievements in the field, such as the application of clusters (fullerenes, nanoparticles, nanotubes) for efficient harmonic generation of ultrashort laser pulses in cluster-containin...

  13. High Accelerating Field Superconducting Radio Frequency Cavities

    Science.gov (United States)

    Orr, R. S.; Saito, K.; Furuta, F.; Saeki, T.; Inoue, H.; Morozumi, Y.; Higo, T.; Higashi, Y.; Matsumoto, H.; Kazakov, S.; Yamaoka, H.; Ueno, K.; Sato, M.

    2008-06-01

    We have conducted a study of a series of single cell superconducting RF cavities at KEK. These tests were designed to investigate the effect of surface treatment on the maximum accelerating field attainable. All of these cavities are of the ICHIRO shape, based on the Low Loss shape. Our results indicate that accelerating fields as high as the theoretical maximum of 50MV/m are attainable.

  14. Study of a contracted glow in low-frequency plasma-jet discharges operating with argon

    Energy Technology Data Exchange (ETDEWEB)

    Minotti, F.; Giuliani, L.; Xaubet, M.; Grondona, D. [Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, C1428EHA, Buenos Aires, Argentina and Instituto de Física del Plasma (INFIP), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires - UBA, C1428EHA, Buenos Aires (Argentina)

    2015-11-15

    In this work, we present an experimental and theoretical study of a low frequency, atmospheric plasma-jet discharge in argon. The discharge has the characteristics of a contracted glow with a current channel of submillimeter diameter and a relatively high voltage cathode layer. In order to interpret the measurements, we consider the separate modeling of each region of the discharge: main channel and cathode layer, which must then be properly matched together. The main current channel was modeled, extending a previous work, as similar to an arc in which joule heating is balanced by lateral heat conduction, without thermal equilibrium between electrons and heavy species. The cathode layer model, on the other hand, includes the emission of secondary electrons by ion impact and by additional mechanisms, of which we considered emission due to collision of atoms excited at metastable levels, and field-enhanced thermionic emission (Schottky effect). The comparison of model and experiment indicates that the discharge can be effectively sustained in its contracted form by the secondary electrons emitted by collision of excited argon atoms, whereas thermionic emission is by far insufficient to provide the necessary electrons.

  15. Radio Frequency Plasma Discharge Lamps for Use as Stable Calibration Light Sources

    Science.gov (United States)

    McAndrew, Brendan; Cooper, John; Arecchi, Angelo; McKee, Greg; Durell, Christopher

    2012-01-01

    Stable high radiance in visible and near-ultraviolet wavelengths is desirable for radiometric calibration sources. In this work, newly available electrodeless radio-frequency (RF) driven plasma light sources were combined with research grade, low-noise power supplies and coupled to an integrating sphere to produce a uniform radiance source. The stock light sources consist of a 28 VDC power supply, RF driver, and a resonant RF cavity. The RF cavity includes a small bulb with a fill gas that is ionized by the electric field and emits light. This assembly is known as the emitter. The RF driver supplies a source of RF energy to the emitter. In commercial form, embedded electronics within the RF driver perform a continual optimization routine to maximize energy transfer to the emitter. This optimization routine continually varies the light output sinusoidally by approximately 2% over a several-second period. Modifying to eliminate this optimization eliminates the sinusoidal variation but allows the output to slowly drift over time. This drift can be minimized by allowing sufficient warm-up time to achieve thermal equilibrium. It was also found that supplying the RF driver with a low-noise source of DC electrical power improves the stability of the lamp output. Finally, coupling the light into an integrating sphere reduces the effect of spatial fluctuations, and decreases noise at the output port of the sphere.

  16. Theoretical study of very low-frequency wave heating of a fusion plasma

    International Nuclear Information System (INIS)

    Fiori, C.

    1980-12-01

    For a certain order of frequencies defined here we give the derivation and general solution of the 4th order differential equation obeyed by the radial MHD displacement of a cylindrical, resistive and incompressible plasma column. By means of a flux function the expressions of the elctromagnetic field and the current density in the resistive layer are obtained the power dissipated in this layer by an external wave and its limit when the resistivity disappears are then discussed [fr

  17. Branched carbon nanofiber network synthesis at room temperature using radio frequency supported microwave plasmas

    OpenAIRE

    Boskovic, BO; Stolojan, V; Zeze, DA; Forrest, RD; Silva, SRP; Haq, S

    2004-01-01

    Carbon nanofibers have been grown at room temperature using a combination of radio frequency and microwave assisted plasma-enhanced chemical vapor deposition. The nanofibers were grown, using Ni powder catalyst, onto substrates kept at room temperature by using a purposely designed water-cooled sample holder. Branched carbon nanofiber growth was obtained without using a template resulting in interconnected carbon nanofiber network formation on substrates held at room temperatur...

  18. Super-high magnetic fields in spatially inhomogeneous plasma

    International Nuclear Information System (INIS)

    Nastoyashchiy, Anatoly F.

    2012-01-01

    The new phenomenon of a spontaneous magnetic field in spatially inhomogeneous plasma is found. The criteria for instability are determined, and both the linear and nonlinear stages of the magnetic field growth are considered; it is shown that the magnetic field can reach a considerable magnitude, namely, its pressure can be comparable with the plasma pressure. Especially large magnetic fields can arise in hot plasma with a high electron density, for example, in laser-heated plasma. In steady-state plasma, the magnetic field can be self-sustaining. The considered magnetic fields may play an important role in thermal insulation of the plasma. (author)

  19. Frequency-Domain Tomography for Single-shot, Ultrafast Imaging of Evolving Laser-Plasma Accelerators

    Science.gov (United States)

    Li, Zhengyan; Zgadzaj, Rafal; Wang, Xiaoming; Downer, Michael

    2011-10-01

    Intense laser pulses propagating through plasma create plasma wakefields that often evolve significantly, e.g. by expanding and contracting. However, such dynamics are known in detail only through intensive simulations. Laboratory visualization of evolving plasma wakes in the ``bubble'' regime is important for optimizing and scaling laser-plasma accelerators. Recently snap-shots of quasi-static wakes were recorded using frequency-domain holography (FDH). To visualize the wake's evolution, we have generalized FDH to frequency-domain tomography (FDT), which uses multiple probes propagating at different angles with respect to the pump pulse. Each probe records a phase streak, imprinting a partial record of the evolution of pump-created structures. We then topographically reconstruct the full evolution from all phase streaks. To prove the concept, a prototype experiment visualizing nonlinear index evolution in glass is demonstrated. Four probes propagating at 0, 0.6, 2, 14 degrees to the index ``bubble'' are angularly and temporally multiplexed to a single spectrometer to achieve cost-effective FDT. From these four phase streaks, an FDT algorithm analogous to conventional CT yields a single-shot movie of the pump's self-focusing dynamics.

  20. Capacitively coupled radio-frequency plasmas excited by tailored voltage waveforms

    International Nuclear Information System (INIS)

    Lafleur, T; Delattre, P A; Booth, J P; Johnson, E V

    2013-01-01

    By applying certain types of ‘tailored’ voltage waveforms (TVWs) to capacitively coupled plasmas, a dc self-bias and an asymmetric plasma response can be produced, even in geometrically symmetric reactors. Furthermore, these arbitrary applied waveforms can produce a number of interesting phenomena that are not present in typical single-frequency sinusoidal discharges. This electrical asymmetry effect presents emerging possibilities for the improved control of the ion energy and ion flux in these systems; parameters of vital importance to both etching and deposition applications for materials processing. With a combined research approach utilizing both experimental measurements, and particle-in-cell simulations, we review and extend recent investigations that study a particular class of TVW. The waveforms used have a pulse-type shape and are composed of a varying number of harmonic frequencies. This allows a strong self-bias to be produced, and causes most of the applied voltage to be dropped across a single sheath. Additionally, decreasing the pulse width (by increasing the number of harmonics), allows the plasma density and ion flux to be increased. Simulation and experimental results both demonstrate that this type of waveform can be used to separately control the ion flux and ion energy, while still producing a uniform plasma over large area (50 cm diameter) rf electrodes. (paper)

  1. Investigation of the LAPPS Ion Flux to a Surface Biased with an Arbitrary High Frequency Waveform

    Science.gov (United States)

    Blackwell, David; Walton, Scott; Leonhardt, Darrin; Murphy, Donald; Fernsler, Richard; Meger, Robert

    2001-10-01

    Materials etching using accelerated ions has become a widely used procedure in the semiconductor industry. Typically the substrate is biased with high frequency voltage waveforms, which cause the substrate to acquire a negative DC voltage to accelerate the ions. However, the ions do not reach the substrate as a monoenergetic beam. The ion energy distribution function (IEDF) is profoundly influenced by the frequency and shape of the applied waveform. At NRL, we have been experimenting with electron-beam produced plasmas as an alternative to radiofrequency (RF) driven discharges. The most promising of these sources is the hollow cathode driven \\underlineLarge \\underlineArea \\underlinePlasma \\underlineProcessing \\underlineSystem. This source is designed to produce large area (> 1 m^2), high density, uniform sheets of plasma. In this presentation we will show measurements of the ion energy distribution function (IEDF) from continuous and pulsed electron beam plasmas produced in 20-30 cm wide × 1 cm thick sheets by a 2 kV hollow cathode. The IEDF is obtained using a gridded energy analyzer incorporated into a biasable stage. The surface flux and IEDF as a function of the waveform input to the stage will be investigated by using various types of pulse functions and variable frequency RF voltages. Typical operating conditions are 15-20 millitorr of argon, oxygen, or nitrogen, and 150-200 Gauss magnetic field.

  2. Improving mental task classification by adding high frequency band information.

    Science.gov (United States)

    Zhang, Li; He, Wei; He, Chuanhong; Wang, Ping

    2010-02-01

    Features extracted from delta, theta, alpha, beta and gamma bands spanning low frequency range are commonly used to classify scalp-recorded electroencephalogram (EEG) for designing brain-computer interface (BCI) and higher frequencies are often neglected as noise. In this paper, we implemented an experimental validation to demonstrate that high frequency components could provide helpful information for improving the performance of the mental task based BCI. Electromyography (EMG) and electrooculography (EOG) artifacts were removed by using blind source separation (BSS) techniques. Frequency band powers and asymmetry ratios from the high frequency band (40-100 Hz) together with those from the lower frequency bands were used to represent EEG features. Finally, Fisher discriminant analysis (FDA) combining with Mahalanobis distance were used as the classifier. In this study, four types of classifications were performed using EEG signals recorded from four subjects during five mental tasks. We obtained significantly higher classification accuracy by adding the high frequency band features compared to using the low frequency bands alone, which demonstrated that the information in high frequency components from scalp-recorded EEG is valuable for the mental task based BCI.

  3. Chaos in high-power high-frequency gyrotrons

    International Nuclear Information System (INIS)

    Airila, M.

    2004-01-01

    Gyrotron interaction is a complex nonlinear dynamical process, which may turn chaotic in certain circumstances. The emergence of chaos renders dynamical systems unpredictable and causes bandwidth broadening of signals. Such effects would jeopardize the prospect of advanced gyrotrons in fusion. Therefore, it is important to be aware of the possibility of chaos in gyrotrons. There are three different chaos scenarios closely related to the development of high-power gyrotrons: First, the onset of chaos in electron trajectories would lead to difficulties in the design and efficient operation of depressed potential collectors, which are used for efficiency enhancement. Second, the radio-frequency signal could turn chaotic, decreasing the output power and the spectral purity of the output signal. As a result, mode conversion, transmission, and absorption efficiencies would be reduced. Third, spatio-temporal chaos in the resonator field structure can set a limit for the use of large-diameter interaction cavities and high-order TE modes (large azimuthal index) allowing higher generated power. In this thesis, the issues above are addressed with numerical modeling. It is found that chaos in electron residual energies is practically absent in the parameter region corresponding to high efficiency. Accordingly, depressed collectors are a feasible solution also in advanced high-power gyrotrons. A new method is presented for straightforward numerical solution of the one-dimensional self-consistent time-dependent gyrotron equations, and the method is generalized to two dimensions. In 1D, a chart of gyrotron oscillations is calculated. It is shown that the regions of stationary oscillations, automodulation, and chaos have a complicated topology in the plane of generalized gyrotron variables. The threshold current for chaotic oscillations exceeds typical operating currents by a factor of ten. However, reflection of the output signal may significantly lower the threshold. 2D

  4. High frequency characterization of Galfenol minor flux density loops

    Directory of Open Access Journals (Sweden)

    Ling Weng

    2017-05-01

    Full Text Available This paper presents the first measurement of ring-shaped Galfenol’s high frequency-dependent minor flux density loops. The frequencies of applied AC magnetic field are 1k, 5k, 10k, 50k, 100k, 200k, 300k, 500 kHz. The measurements show that the cycle area between the flux density and magnetic field curves increase with increasing frequency. High frequency-dependent characterization, including coercivity, specific power loss, residual induction, and maximum relative permeability are discussed. Minor loops for different max induction are also measured and discussed at the same frequency 100 kHz. Minor loops with the same max induction 0.05 T for different frequencies 50, 100, 200, 300, 400 kHz are measured and specific power loss are discussed.

  5. Integrated plasma control for high performance tokamaks

    International Nuclear Information System (INIS)

    Humphreys, D.A.; Deranian, R.D.; Ferron, J.R.; Johnson, R.D.; LaHaye, R.J.; Leuer, J.A.; Penaflor, B.G.; Walker, M.L.; Welander, A.S.; Jayakumar, R.J.; Makowski, M.A.; Khayrutdinov, R.R.

    2005-01-01

    Sustaining high performance in a tokamak requires controlling many equilibrium shape and profile characteristics simultaneously with high accuracy and reliability, while suppressing a variety of MHD instabilities. Integrated plasma control, the process of designing high-performance tokamak controllers based on validated system response models and confirming their performance in detailed simulations, provides a systematic method for achieving and ensuring good control performance. For present-day devices, this approach can greatly reduce the need for machine time traditionally dedicated to control optimization, and can allow determination of high-reliability controllers prior to ever producing the target equilibrium experimentally. A full set of tools needed for this approach has recently been completed and applied to present-day devices including DIII-D, NSTX and MAST. This approach has proven essential in the design of several next-generation devices including KSTAR, EAST, JT-60SC, and ITER. We describe the method, results of design and simulation tool development, and recent research producing novel approaches to equilibrium and MHD control in DIII-D. (author)

  6. High-frequency multimodal atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Adrian P. Nievergelt

    2014-12-01

    Full Text Available Multifrequency atomic force microscopy imaging has been recently demonstrated as a powerful technique for quickly obtaining information about the mechanical properties of a sample. Combining this development with recent gains in imaging speed through small cantilevers holds the promise of a convenient, high-speed method for obtaining nanoscale topography as well as mechanical properties. Nevertheless, instrument bandwidth limitations on cantilever excitation and readout have restricted the ability of multifrequency techniques to fully benefit from small cantilevers. We present an approach for cantilever excitation and deflection readout with a bandwidth of 20 MHz, enabling multifrequency techniques extended beyond 2 MHz for obtaining materials contrast in liquid and air, as well as soft imaging of delicate biological samples.

  7. High quality factor gigahertz frequencies in nanomechanical diamond resonators

    OpenAIRE

    Gaidarzhy, Alexei; Imboden, Matthias; Mohanty, Pritiraj; Rankin, Janet; Sheldon, Brian W.

    2007-01-01

    We report actuation and detection of gigahertz-range resonance frequencies in nano-crystalline diamond mechanical resonators. High order transverse vibration modes are measured in coupled-beam resonators exhibiting frequencies up to 1.441 GHz. The cantilever-array design of the resonators translates the gigahertz-range resonant motion of micron-long cantilever elements to the displacement of the central supporting structure. Use of nano-crystalline diamond further increases the frequency comp...

  8. Study of electron current extraction from a radio frequency plasma cathode designed as a neutralizer for ion source applications

    Energy Technology Data Exchange (ETDEWEB)

    Jahanbakhsh, Sina, E-mail: sinajahanbakhsh@gmail.com; Satir, Mert; Celik, Murat [Department of Mechanical Engineering, Bogazici University, Istanbul 34342 (Turkey)

    2016-02-15

    Plasma cathodes are insert free devices that are developed to be employed as electron sources in electric propulsion and ion source applications as practical alternatives to more commonly used hollow cathodes. Inductively coupled plasma cathodes, or Radio Frequency (RF) plasma cathodes, are introduced in recent years. Because of its compact geometry, and simple and efficient plasma generation, RF plasma source is considered to be suitable for plasma cathode applications. In this study, numerous RF plasma cathodes have been designed and manufactured. Experimental measurements have been conducted to study the effects of geometric and operational parameters. Experimental results of this study show that the plasma generation and electron extraction characteristics of the RF plasma cathode device strongly depend on the geometric parameters such as chamber diameter, chamber length, orifice diameter, orifice length, as well as the operational parameters such as RF power and gas mass flow rate.

  9. High-frequency energy in singing and speech

    Science.gov (United States)

    Monson, Brian Bruce

    While human speech and the human voice generate acoustical energy up to (and beyond) 20 kHz, the energy above approximately 5 kHz has been largely neglected. Evidence is accruing that this high-frequency energy contains perceptual information relevant to speech and voice, including percepts of quality, localization, and intelligibility. The present research was an initial step in the long-range goal of characterizing high-frequency energy in singing voice and speech, with particular regard for its perceptual role and its potential for modification during voice and speech production. In this study, a database of high-fidelity recordings of talkers was created and used for a broad acoustical analysis and general characterization of high-frequency energy, as well as specific characterization of phoneme category, voice and speech intensity level, and mode of production (speech versus singing) by high-frequency energy content. Directionality of radiation of high-frequency energy from the mouth was also examined. The recordings were used for perceptual experiments wherein listeners were asked to discriminate between speech and voice samples that differed only in high-frequency energy content. Listeners were also subjected to gender discrimination tasks, mode-of-production discrimination tasks, and transcription tasks with samples of speech and singing that contained only high-frequency content. The combination of these experiments has revealed that (1) human listeners are able to detect very subtle level changes in high-frequency energy, and (2) human listeners are able to extract significant perceptual information from high-frequency energy.

  10. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Shahid, E-mail: shahid.ahmed@ieee.org [BML Munjal University, Gurgaon, Haryana 123413 (India); Mammosser, John D. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2015-07-15

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar–O{sub 2} (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM{sub 010}-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

  11. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity

    Science.gov (United States)

    Ahmed, Shahid; Mammosser, John D.

    2015-07-01

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar-O2 (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM010-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

  12. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity

    International Nuclear Information System (INIS)

    Ahmed, Shahid; Mammosser, John D.

    2015-01-01

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar–O 2 (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM 010 -mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper

  13. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity.

    Science.gov (United States)

    Ahmed, Shahid; Mammosser, John D

    2015-07-01

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar-O2 (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM010-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

  14. The Influence of High-Frequency Envelope Information on Low-Frequency Vowel Identification in Noise.

    Directory of Open Access Journals (Sweden)

    Wiebke Schubotz

    Full Text Available Vowel identification in noise using consonant-vowel-consonant (CVC logatomes was used to investigate a possible interplay of speech information from different frequency regions. It was hypothesized that the periodicity conveyed by the temporal envelope of a high frequency stimulus can enhance the use of the information carried by auditory channels in the low-frequency region that share the same periodicity. It was further hypothesized that this acts as a strobe-like mechanism and would increase the signal-to-noise ratio for the voiced parts of the CVCs. In a first experiment, different high-frequency cues were provided to test this hypothesis, whereas a second experiment examined more closely the role of amplitude modulations and intact phase information within the high-frequency region (4-8 kHz. CVCs were either natural or vocoded speech (both limited to a low-pass cutoff-frequency of 2.5 kHz and were presented in stationary 3-kHz low-pass filtered masking noise. The experimental results did not support the hypothesized use of periodicity information for aiding low-frequency perception.

  15. The Influence of High-Frequency Envelope Information on Low-Frequency Vowel Identification in Noise.

    Science.gov (United States)

    Schubotz, Wiebke; Brand, Thomas; Kollmeier, Birger; Ewert, Stephan D

    2016-01-01

    Vowel identification in noise using consonant-vowel-consonant (CVC) logatomes was used to investigate a possible interplay of speech information from different frequency regions. It was hypothesized that the periodicity conveyed by the temporal envelope of a high frequency stimulus can enhance the use of the information carried by auditory channels in the low-frequency region that share the same periodicity. It was further hypothesized that this acts as a strobe-like mechanism and would increase the signal-to-noise ratio for the voiced parts of the CVCs. In a first experiment, different high-frequency cues were provided to test this hypothesis, whereas a second experiment examined more closely the role of amplitude modulations and intact phase information within the high-frequency region (4-8 kHz). CVCs were either natural or vocoded speech (both limited to a low-pass cutoff-frequency of 2.5 kHz) and were presented in stationary 3-kHz low-pass filtered masking noise. The experimental results did not support the hypothesized use of periodicity information for aiding low-frequency perception.

  16. High frequency single mode traveling wave structure for particle acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Ivanyan, M.I.; Danielyan, V.A.; Grigoryan, B.A.; Grigoryan, A.H. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Tsakanian, A.V. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Technische Universität Darmstadt, Institut TEMF, 64289 Darmstadt (Germany); Tsakanov, V.M., E-mail: tsakanov@asls.candle.am [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Vardanyan, A.S.; Zakaryan, S.V. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia)

    2016-09-01

    The development of the new high frequency slow traveling wave structures is one of the promising directions in accomplishment of charged particles high acceleration gradient. The disc and dielectric loaded structures are the most known structures with slowly propagating modes. In this paper a large aperture high frequency metallic two-layer accelerating structure is studied. The electrodynamical properties of the slowly propagating TM{sub 01} mode in a metallic tube with internally coated low conductive thin layer are examined.

  17. The importance of dose, frequency and duration of vitamin D supplementation for plasma 25-hydroxyvitamin D.

    Science.gov (United States)

    Chao, Yi-Sheng; Brunel, Ludovic; Faris, Peter; Veugelers, Paul J

    2013-10-11

    The importance of dose, frequency and duration of vitamin D supplementation for plasma 25(OH)D levels is not well described and rarely reported for supplementation that exceeds 2000 IU per day. The objective is to examine dose, frequency and duration of supplementation in relation to plasma 25(OH)D in a large population-based sample. We accessed data on 2714 volunteers that contributed to 4224 visits and applied multilevel regression. Compared to not using supplements, a minimum regimen of 1000-2000 IU once or twice per week for one month was not effective in raising 25(OH)D. Compared to this minimum regimen, higher doses of 2000-3000, 3000-4000, and 5000 IU or more were associated with a 7.49, 13.19 and 30.22 nmol/L 25(OH)D increase, respectively; frequencies of three to four, five to six and seven times/week were associated with a 5.44, 16.52 and 30.69 nmol/L increase, respectively; and supplementation of five months or longer was associated with an increase of 6.68 nmol/L (p D. Whereas dose, frequency and duration of supplementation are important to healthy subjects committed to optimizing their nutritional status, to the design of clinical trials, individual characteristics and lifestyle contribute substantially to 25(OH)D.

  18. Comparative study of atmospheric pressure low and radio frequency microjet plasmas produced in a single electrode configuration

    International Nuclear Information System (INIS)

    Kim, Dan Bee; Rhee, J. K.; Gweon, B.; Moon, S. Y.; Choe, W.

    2007-01-01

    Microsize jet-type plasmas were generated in a single pin electrode structure source for two separate input frequencies of 50 kHz and 13.56 MHz in the ambient air. The copper pin electrode radius was 360 μm, and it was placed in a Pyrex tube with a radius of 3 mm for helium gas supply. Due to the input frequency difference, the generated plasmas showed distinct discharge characteristics for their plasma physical appearances, electrical properties, gas temperatures, and optical properties. Strengths and weaknesses of both plasmas were discussed for further applications

  19. High-Speed Imaging of Dusty Plasma Instabilities

    International Nuclear Information System (INIS)

    Tawidian, H.; Mikikian, M.; Lecas, T.; Boufendi, L.; Coueedel, L.; Vallee, O.

    2011-01-01

    Dust particles in a plasma acquire negative charges by capturing electrons. If the dust particle density is high, a huge loss of free electrons can trigger unstable behaviors in the plasma. Several types of plasma behaviors are analyzed thanks to a high-speed camera like dust particle growth instabilities (DPGI) and a new phenomenon called plasma spheroids. These small plasma spheroids are about a few mm, have a slightly enhanced luminosity, and are observed in the vicinity of the electrodes. Different behaviors are identified for these spheroids like a rotational motion, or a chaotic regime (fast appearance and disappearance).

  20. High-Speed Imaging of Dusty Plasma Instabilities

    Science.gov (United States)

    Tawidian, H.; Couëdel, L.; Mikikian, M.; Lecas, T.; Boufendi, L.; Vallée, O.

    2011-11-01

    Dust particles in a plasma acquire negative charges by capturing electrons. If the dust particle density is high, a huge loss of free electrons can trigger unstable behaviors in the plasma. Several types of plasma behaviors are analyzed thanks to a high-speed camera like dust particle growth instabilities (DPGI) and a new phenomenon called plasma spheroids. These small plasma spheroids are about a few mm, have a slightly enhanced luminosity, and are observed in the vicinity of the electrodes. Different behaviors are identified for these spheroids like a rotational motion, or a chaotic regime (fast appearance and disappearance).

  1. Fokker-Planck description of the scattering of radio frequency waves at the plasma edge

    International Nuclear Information System (INIS)

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

    2010-01-01

    In magnetic fusion devices, radio frequency (rf) waves in the electron cyclotron (EC) and lower hybrid (LH) range of frequencies are being commonly used to modify the plasma current profile. In ITER, EC waves are expected to stabilize the neoclassical tearing mode (NTM) by providing current in the island region [R. Aymar et al., Nucl. Fusion 41, 1301 (2001)]. The appearance of NTMs severely limits the plasma pressure and leads to the degradation of plasma confinement. LH waves could be used in ITER to modify the current profile closer to the edge of the plasma. These rf waves propagate from the excitation structures to the core of the plasma through an edge region, which is characterized by turbulence--in particular, density fluctuations. These fluctuations, in the form of blobs, can modify the propagation properties of the waves by refraction. In this paper, the effect on rf due to randomly distributed blobs in the edge region is studied. The waves are represented as geometric optics rays and the refractive scattering from a distribution of blobs is formulated as a Fokker-Planck equation. The scattering can have two diffusive effects--one in real space and the other in wave vector space. The scattering can modify the trajectory of rays into the plasma and it can affect the wave vector spectrum. The refraction of EC waves, for example, could make them miss the intended target region where the NTMs occur. The broadening of the wave vector spectrum could broaden the wave generated current profile. The Fokker-Planck formalism for diffusion in real space and wave vector space is used to study the effect of density blobs on EC and LH waves in an ITER type of plasma environment. For EC waves the refractive effects become important since the distance of propagation from the edge to the core in ITER is of the order of a meter. The diffusion in wave vector space is small. For LH waves the refractive effects are insignificant but the diffusion in wave vector space is

  2. Ion collection from laser-induced plasma by applying radio-frequency voltage

    International Nuclear Information System (INIS)

    Shibata, Takemasa; Ogura, Koichi

    1995-01-01

    Ions were collected on the electrodes from a laser resonance photoionized plasma by applying 1.8MHz radio-frequency voltage to the electrode. It was demonstrated that the ions are collected in a shorter time at the same kinetic energy of the collected ions compared with ion collection by applying DC voltage to the electrode. A simple one-dimensional model was extended for prediction of ion collection times in the cases of applications of not only the DC voltage but also the radio-frequency voltage. The ion collection times estimated using the simple one-dimensional model agreed with experimental values in both cases of DC and radio-frequency voltages. (author)

  3. Nonlinear gyrokinetic equations for low-frequency electromagnetic waves in general plasma equilibria

    International Nuclear Information System (INIS)

    Frieman, E.A.; Chen, L.

    1981-10-01

    A nonlinear gyrokinetic formalism for low-frequency (less than the cyclotron frequency) microscopic electromagnetic perturbations in general magnetic field configurations is developed. The nonlinear equations thus derived are valid in the strong-turbulence regime and contain effects due to finite Larmor radius, plasma inhomogeneities, and magentic field geometries. The specific case of axisymmetric tokamaks is then considered, and a model nonlinear equation is derived for electrostatic drift waves. Also, applying the formalism to the shear Alfven wave heating sceme, it is found that nonlinear ion Landau damping of kinetic shear-Alfven waves is modified, both qualitatively and quantitatively, by the diamagnetic drift effects. In particular, wave energy is found to cascade in wavenumber instead of frequency

  4. EDITORIAL: The interaction of radio-frequency fields with fusion plasmas: the JET experience The interaction of radio-frequency fields with fusion plasmas: the JET experience

    Science.gov (United States)

    Ongena, Jef

    2012-07-01

    The JET Task Force Heating is proud to present this special issue. It is the result of hard and dedicated work by everybody participating in the Task Force over the last four years and gives an overview of the experimental and theoretical results obtained in the period 2008-2010 with radio frequency heating of JET fusion plasmas. Topics studied and reported in this issue are: investigations into the operation of lower hybrid heating accompanied by new modeling results; new experimental results and insights into the physics of various ion cyclotron range of frequencies (ICRF) heating scenarios; progress in studies of intrinsic and ion cyclotron wave-induced plasma rotation and flows; a summary of the developments over the last years in designing an ion cyclotron radiofrequency heating (ICRH) system that can cope with the presence of fast load variations in the edge, as e.g. caused by pellets or edge localized modes (ELMs) during H-Mode operation; an overview of the results obtained with the ITER-like antenna operating in H-Mode with a packed array of straps and power densities close to those of the projected ITER ICRH antenna; and, finally, a summary of the results obtained in applying ion cyclotron waves for wall conditioning of the tokamak. This issue would not have been possible without the strong motivation and efforts (sometimes truly heroic) of all colleagues of the JET Task Force Heating. A sincere word of thanks, therefore, to all authors and co-authors involved in the experiments, analysis and compilation of the papers. It was a special privilege to work with all of them during the past very intense years. Thanks also to all other European and non-European scientists who contributed to the JET scientific programme, the operations team of JET and the colleagues of the Close Support Unit in Culham. Thanks also to the editors, Editorial Board and referees of Plasma Physics and Controlled Fusion, together with the publishing staff of IOPP, who have not only

  5. [Demography and donation frequencies of blood and plasma donor populations in Germany].

    Science.gov (United States)

    Ritter, Sabine; Willand, L; Reinhard, B; Offergeld, R; Hamouda, O

    2008-08-01

    According to Article 22 of the Transfusion Act, the Robert Koch Institute collects and evaluates nationwide data on the prevalence and incidence of transfusion-relevant infections among blood and plasma donors in Germany. Due to revision of the Transfusion Act in 2005 not only the number of donations but also the number of donors has become available for analysis. Here we give a detailed account on the demographic profile and donation frequencies of German whole blood, plasma and platelet donors in 2006. Overall, 4 % of the German population eligible to donate were active as repeat whole blood donors in 2006; 0.3 % repeatedly donated plasma or platelets. Irrespective of the type of donation, the percentage of donors among the general population was highest among the youngest age group (18 to 24 years). While the age distribution of whole blood repeat donors roughly resembled that of the general population, with the greatest number among those aged 35 to 44, younger age groups were overrepresented among repeat plasma donors. Donation frequency varied depending on donor age and sex, with an average of 1.9 per year for whole blood donations, 11.9 for plasmapheresis and 4.0 for plateletpheresis. With the exception of the latter, men donated more frequently than women. For both sexes, donation frequency increased with age. Detailed knowledge of the demographic profile and changes in the composition of donor populations are essential for planning adequate blood supply. The data presented may serve as reference for assessing the consequences of measures that affect the number of donors and/or donations (for example changing deferral criteria) in Germany.

  6. High density plasma heating in the Tokamak à configuration variable

    International Nuclear Information System (INIS)

    Curchod, L.

    2011-04-01

    The Tokamak à Configuration Variable (TCV) is a medium size magnetic confinement thermonuclear fusion experiment designed for the study of the plasma performances as a function of its shape. It is equipped with a high power and highly flexible electron cyclotron heating (ECH) and current drive (ECCD) system. Up to 3 MW of 2 nd harmonic EC power in ordinary (O 2 ) or extraordinary (X 2 ) polarization can be injected from TCV low-field side via six independently steerable launchers. In addition, up to 1.5 MW of 3 rd harmonic EC power (X 3 ) can be launched along the EC resonance from the top of TCV vacuum vessel. At high density, standard ECH and ECCD are prevented by the appearance of a cutoff layer screening the access to the EC resonance at the plasma center. As a consequence, less than 50% of TCV density operational domain is accessible to X 2 and X 3 ECH. The electron Bernstein waves (EBW) have been proposed to overcome this limitation. EBW is an electrostatic mode propagating beyond the plasma cutoff without upper density limit. Since it cannot propagate in vacuum, it has to be excited by mode conversion of EC waves in the plasma. Efficient electron Bernstein waves heating (EBH) and current drive (EBCD) were previously performed in several fusion devices, in particular in the W7-AS stellarator and in the MAST spherical tokamak. In TCV, the conditions for an efficient O-X-B mode conversion (i.e. a steep density gradient at the O 2 plasma cutoff) are met at the edge of high confinement (H-mode) plasmas characterized by the appearance of a pedestal in the electron temperature and density profiles. TCV experiments have demonstrated the first EBW coupling to overdense plasmas in a medium aspect-ratio tokamak via O-X-B mode conversion. This thesis work focuses on several aspects of ECH and EBH in low and high density plasmas. Firstly, the experimental optimum angles for the O-X-B mode conversion is successfully compared to the full-wave mode conversion calculation

  7. 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.

  8. Research on high energy density plasmas and applications

    International Nuclear Information System (INIS)

    1999-01-01

    Recently, technologies on lasers, accelerators, and pulse power machines have been significantly advanced and input power density covers the intensity range from 10 10 W/cm 2 to higher than 10 20 W/cm 2 . As the results, high pressure gas and solid targets can be heated up to very high temperature to create hot dense plasmas which have never appeared on the earth. The high energy density plasmas opened up new research fields such as inertial confinement fusion, high brightness X-ray radiation sources, interiors of galactic nucleus,supernova, stars and planets, ultra high pressure condensed matter physics, plasma particle accelerator, X-ray laser, and so on. Furthermore, since these fields are intimately connected with various industrial sciences and technologies, the high energy density plasma is now studied in industries, government institutions, and so on. This special issue of the Journal of Plasma Physics and Nuclear Fusion Research reviews the high energy density plasma science for the comprehensive understanding of such new fields. In May, 1998, the review committee for investigating the present status and the future prospects of high energy density plasma science was established in the Japan Society of Plasma Science and Nuclear Fusion Research. We held three committee meetings to discuss present status and critical issues of research items related to high energy density plasmas. This special issue summarizes the understandings of the committee. This special issue consists of four chapters: They are Chapter 1: Physics important in the high energy density plasmas, Chapter 2: Technologies related to the plasma generation; drivers such as lasers, pulse power machines, particle beams and fabrication of various targets, Chapter 3: Plasma diagnostics important in high energy density plasma experiments, Chapter 4: A variety of applications of high energy density plasmas; X-ray radiation, particle acceleration, inertial confinement fusion, laboratory astrophysics

  9. Propagation Characteristics of High-Power Vortex Laguerre-Gaussian Laser Beams in Plasma

    Directory of Open Access Journals (Sweden)

    Zhili Lin

    2018-04-01

    Full Text Available The propagation characteristics of high-power laser beams in plasma is an important research topic and has many potential applications in fields such as laser machining, laser-driven accelerators and laser-driven inertial confined fusion. The dynamic evolution of high-power Laguerre-Gaussian (LG beams in plasma is numerically investigated by using the finite-difference time-domain (FDTD method based on the nonlinear Drude model, with both plasma frequency and collision frequency modulated by the light intensity of laser beam. The numerical algorithms and implementation techniques of FDTD method are presented for numerically simulating the nonlinear permittivity model of plasma and generating the LG beams with predefined parameters. The simulation results show that the plasma has different field modulation effects on the two exemplified LG beams with different cross-sectional patterns. The self-focusing and stochastic absorption phenomena of high-power laser beam in plasma are also demonstrated. This research also provides a new means for the field modulation of laser beams by plasma.

  10. Atomic processes in high-density plasmas

    International Nuclear Information System (INIS)

    More, R.M.

    1982-01-01

    This review covers dense atomic plasmas such as that produced in inertial confinement fusion. The target implosion physics along with the associated atomic physics, i.e., free electron collision phenomena, electron states I, electron states II, and nonequilibrium plasma states are described

  11. High density terahertz frequency comb produced by coherent synchrotron radiation

    Science.gov (United States)

    Tammaro, S.; Pirali, O.; Roy, P.; Lampin, J.-F.; Ducournau, G.; Cuisset, A.; Hindle, F.; Mouret, G.

    2015-07-01

    Frequency combs have enabled significant progress in frequency metrology and high-resolution spectroscopy extending the achievable resolution while increasing the signal-to-noise ratio. In its coherent mode, synchrotron radiation is accepted to provide an intense terahertz continuum covering a wide spectral range from about 0.1 to 1 THz. Using a dedicated heterodyne receiver, we reveal the purely discrete nature of this emission. A phase relationship between the light pulses leads to a powerful frequency comb spanning over one decade in frequency. The comb has a mode spacing of 846 kHz, a linewidth of about 200 Hz, a fractional precision of about 2 × 10-10 and no frequency offset. The unprecedented potential of the comb for high-resolution spectroscopy is demonstrated by the accurate determination of pure rotation transitions of acetonitrile.

  12. Three dimensional complex plasma structures in a combined radio frequency and direct current discharge

    International Nuclear Information System (INIS)

    Mitic, S.; Morfill, G. E.; Klumov, B. A.; Khrapak, S. A.

    2013-01-01

    We report on the first detailed analysis of large three dimensional (3D) complex plasma structures in experiments performed in pure rf and combined rf+dc discharge modes. Inductively coupled plasma is generated by an rf coil wrapped around the vertically positioned cylindrical glass tube at a pressure of 0.3 mbar. In addition, dc plasma can be generated by applying voltage to the electrodes at the ends of the tube far from the rf coil. The injected monodisperse particles are levitated in the plasma below the coil. A scanning laser sheet and a high resolution camera are used to determine the 3D positions of about 10 5 particles. The observed bowl-shaped particle clouds reveal coexistence of various structures, including well-distinguished solid-like, less ordered liquid-like, and pronounced string-like phases. New criteria to identify string-like structures are proposed.

  13. Concept Study of Radio Frequency (RF Plasma Thruster for Space Propulsion

    Directory of Open Access Journals (Sweden)

    Anna-Maria Theodora ANDREESCU

    2016-12-01

    Full Text Available Electric thrusters are capable of accelerating ions to speeds that are impossible to reach using chemical reaction. Recent advances in plasma-based concepts have led to the identification of electromagnetic (RF generation and acceleration systems as able to provide not only continuous thrust, but also highly controllable and wide-range exhaust velocities. For Future Space Propulsion there is a pressing need for low pressure, high mass flow rate and controlled ion energies. This paper explores the potential of using RF heated plasmas for space propulsion in order to mitigate the electric propulsion problems caused by erosion and gain flexibility in plasma manipulation. The main key components of RF thruster architecture are: a feeding system able to provide the required neutral gas flow, plasma source chamber, antenna/electrodes wrapped around the discharge tube and optimized electromagnetic field coils for plasma confinement. A preliminary analysis of system performance (thrust, specific impulse, efficiency is performed along with future plans of Space Propulsion based on this new concept of plasma mechanism.

  14. High-Current Plasma Electron Sources

    International Nuclear Information System (INIS)

    Gushenets, J.Z.; Krokhmal, V.A.; Krasik, Ya. E.; Felsteiner, J.; Gushenets, V.

    2002-01-01

    In this report we present the design, electrical schemes and preliminary results of a test of 4 different electron plasma cathodes operating under Kg h-voltage pulses in a vacuum diode. The first plasma cathode consists of 6 azimuthally symmetrically distributed arc guns and a hollow anode having an output window covered by a metal grid. Plasma formation is initiated by a surface discharge over a ceramic washer placed between a W-made cathode and an intermediate electrode. Further plasma expansion leads to a redistribution of the discharge between the W-cathode and the hollow anode. An accelerating pulse applied between the output anode grid and the collector extracts electrons from this plasma. The operation of another plasma cathode design is based on Penning discharge for preliminary plasma formation. The main glow discharge occurs between an intermediate electrode of the Penning gun and the hollow anode. To keep the background pressure in the accelerating gap at P S 2.5x10 4 Torr either differential pumping or a pulsed gas puff valve were used. The operation of the latter electron plasma source is based on a hollow cathode discharge. To achieve a sharp pressure gradient between the cathode cavity and the accelerating gap a pulsed gas puff valve was used. A specially designed ferroelectric plasma cathode initiated plasma formation inside the hollow cathode. This type of the hollow cathode discharge ignition allowed to achieve a discharge current of 1.2 kA at a background pressure of 2x10 4 Torr. All these cathodes were developed and initially tested inside a planar diode with a background pressure S 2x10 4 Torr under the same conditions: accelerating voltage 180 - 300 kV, pulse duration 200 - 400 ns, electron beam current - 1 - 1.5 kA, and cross-sectional area of the extracted electron beam 113 cm 2

  15. Pulsed high-density plasmas for advanced dry etching processes

    International Nuclear Information System (INIS)

    Banna, Samer; Agarwal, Ankur; Cunge, Gilles; Darnon, Maxime; Pargon, Erwine; Joubert, Olivier

    2012-01-01

    Plasma etching processes at the 22 nm technology node and below will have to satisfy multiple stringent scaling requirements of microelectronics fabrication. To satisfy these requirements simultaneously, significant improvements in controlling key plasma parameters are essential. Pulsed plasmas exhibit considerable potential to meet the majority of the scaling challenges, while leveraging the broad expertise developed over the years in conventional continuous wave plasma processing. Comprehending the underlying physics and etching mechanisms in pulsed plasma operation is, however, a complex undertaking; hence the full potential of this strategy has not yet been realized. In this review paper, we first address the general potential of pulsed plasmas for plasma etching processes followed by the dynamics of pulsed plasmas in conventional high-density plasma reactors. The authors reviewed more than 30 years of academic research on pulsed plasmas for microelectronics processing, primarily for silicon and conductor etch applications, highlighting the potential benefits to date and challenges in extending the technology for mass-production. Schemes such as source pulsing, bias pulsing, synchronous pulsing, and others in conventional high-density plasma reactors used in the semiconductor industry have demonstrated greater flexibility in controlling critical plasma parameters such as ion and radical densities, ion energies, and electron temperature. Specifically, plasma pulsing allows for independent control of ion flux and neutral radicals flux to the wafer, which is key to eliminating several feature profile distortions at the nanometer scale. However, such flexibility might also introduce some difficulty in developing new etching processes based on pulsed plasmas. Therefore, the main characteristics of continuous wave plasmas and different pulsing schemes are compared to provide guidelines for implementing different schemes in advanced plasma etching processes based on

  16. High Energy Single Frequency Resonant Amplifier, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR phase I project proposes a single frequency high energy resonant amplifier for remote sensing. Current state-of-art technologies can not provide all...

  17. Oscillographic Chronopotentiometry with High and Low Frequency Current

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A novel electroanalytical method, oscillographic chronopotentiometry with high and low frequency current, is presented in this paper. With this method, the sensitivity of almost all kinds of oscillographic chronopotentiometry can be enhanced about one order.

  18. High-Frequency Microwave Processing of Materials Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Conducts research on high-frequency microwave processing of materials using a highpower, continuous-wave (CW), 83-GHz, quasi-optical beam system for rapid,...

  19. High-frequency matrix converter with square wave input

    Science.gov (United States)

    Carr, Joseph Alexander; Balda, Juan Carlos

    2015-03-31

    A device for producing an alternating current output voltage from a high-frequency, square-wave input voltage comprising, high-frequency, square-wave input a matrix converter and a control system. The matrix converter comprises a plurality of electrical switches. The high-frequency input and the matrix converter are electrically connected to each other. The control system is connected to each switch of the matrix converter. The control system is electrically connected to the input of the matrix converter. The control system is configured to operate each electrical switch of the matrix converter converting a high-frequency, square-wave input voltage across the first input port of the matrix converter and the second input port of the matrix converter to an alternating current output voltage at the output of the matrix converter.

  20. Instrumentation for high-frequency meteorological observations from research vessel

    Digital Repository Service at National Institute of Oceanography (India)

    VijayKumar, K.; Khalap, S.; Mehra, P.

    Ship provides an attractive platform from which high-frequency meteorological observations (e.g., wind components, water vapor density, and air temperature) can be made accurately. However, accurate observations of meteorological variables depend...