共查询到20条相似文献,搜索用时 31 毫秒
1.
Reinmann J. J. Lauver M. R. Patch R. W. Posta S. J. Snyder A. Englert G. W. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1975,3(1):6-14
Initial empirical results are presented for the hot-ion plasma heating experiments conducted in the new SUMMA (Superconducting Magnetic Mirror Apparatus) at NASA Lewis Research Center. A discharge was formed by applying a radially inward DC electric field near the mirror throats. Data were obtained at midplane magnetic flux densities from 1.0 to 3.5 tesla. Charge-exchange neutral particle energy analyzer data were reduced to ion temperatures using a plasma model that included a Maxwellian energy distribution super-imposed on an azimuthal drift, finite ion orbits, and radial variations in density and electric field. Using this plasma model, the highest ion temperatures computed were 5 keV, 1.2 keV, and 1 keV for He+, H2+, and H+, respectively. These were obtained at a mid-plane magnetic flux density of 1.6 T. Ion temperature was found to scale roughly as (P/B)n, where P/B is the ratio of power input to magnetic flux density and n is about 1 for hydrogen and 2 for helium. Optical spectroscopy line-broadening measurements yielded ion temperatures about 15 percent higher than the charge-exchange neutral particle analyzer results for hydrogen and about 50 percent higher for helium. Spectroscopically obtained electron temperatures ranged from 3 to 30 eV. 相似文献
2.
N. Krause B. Hillenbrand Y. Uzel K. Schnitzke 《Applied Physics A: Materials Science & Processing》1983,30(2):67-71
Thin-wall TM010-resonators of cylindrical and spherical shape were made from niobium sheets and investigated experimentally in the frequency range around 10 GHz. In many cases critical magnetic flux-densities up to 90mT — corresponding to accelerating fields of nearly 23 MV/m — and unloaded Q's up to 1010 were reached at a temperature of 1.3K. Measuring the thermal conductivity we found that the originally cold worked niobium is annealed by electron beam welding, and we could calculate thermal limits of flux density. Comparing experimental and calculated critical flux densities we conclude that we are near the thermal limit and no essential improvement is possible. The resonators were also coated with Nb3Sn. In this case critical flux densities of up to 70 mT and unloaded Q's of about 109 were measured at 4.2K and 1.5K. 相似文献
3.
《Journal of Quantitative Spectroscopy & Radiative Transfer》1987,38(3):209-210
The asymmetry parameter δI of the Hβ central part has been measured as a function of the plasma electron density. The results are compared with recently published theories and measurements. The plasma source was a small electromagnetic T-shaped shock tube. The electron density varied between 0.7 x 1023 and 3 x 1023m-3, while the temperatures were 20,000 K and more. 相似文献
4.
L. Torrisi A. Borrielli D. Margarone F. Caridi A. M. Mezzasalma 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):343-348
A pulsed Nd:Yag laser, at intensities of the order of 1010 W/cm2, is employed to irradiate different thick metallic targets (Ti, Fe, Ag, and Ni) placed in vacuum. The obtained non-equilibrium
plasmas are investigated with various analytical techniques. An electrostatic ion energy analyzer and different ion collectors
are employed to monitor in situ the ions ejected from the plasma and to determine the core plasma temperature, the ion energy
distributions and the ion angular emission. An optical spectrometer is employed to analyze the plasma corona emitted light
vs. wavelength and to identify the emitted characteristic lines. The optical spectroscopy permitted to evaluate the electron
temperatures and densities. Results show strong temperature and density gradients occurring in the laser-generated plasma
plume. 相似文献
5.
M. I. Guseva V. M. Gureev L. S. Danelyan B. N. Kolbasov S. N. Korshunov Yu. V. Sereda V. G. Stolyarova V. V. Zatekin V. S. Kulikauskas 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2008,2(2):274-276
Beryllium targets placed in the PLAST beam-plasma discharge facility were irradiated with a flux of stationary deuterium (D) plasma with a deuterium ion energy of 200 eV and plasma flux density of 3 × 1020 m?2 s?1 at temperatures of 370 and 670 K. The irradiation doses varied from 5 × 1021 to 1024 m?2. To heat the target and to ionize impurities near its surface the target was irradiated with an electron beam. The deuterium concentration at the target center exceeds its concentration at the periphery by a factor of more than two under all irradiation conditions. The target center was enriched with carbon up to 16–24 at %, as compared to 4–6 at % at the target periphery. The [D]: [Be] atomic concentration ratios at the target center were equal to 0.054 and 0.036 against 0.024 and 0.016 at the periphery at temperatures of 370 and 670 K, respectively. It has been found that these ratios depend on the concentration of carbon atoms which trapped deuterium atoms. 相似文献
6.
《Journal of Quantitative Spectroscopy & Radiative Transfer》1986,36(4):339-344
Using a detailed atomic model of K shell aluminum ions, we have calculated four diagnostic resonance line ratios as a function of temperature and density for cylindrical aluminum plasmas of diameter 50 and 100 μm, assumed in collisional-radiative equilibrium. The ion densities vary from 1019 cm-3 to 1021 cm-3, the temperatures range from 200 to 700 eV. The conditions are applicable to experiments using the spot spectroscopy technique for plasma diagnosis. 相似文献
7.
V. Milosavljević S. Djeniže 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(1):99-104
Characteristics of the Stark broadened and overlapping 447.1 nm He I spectral line and its forbidden 447.0 nm components have
been measured at electron densities between 4.4×1022 m-3 and 8.2×1022 m-3 and electron temperatures between 18 000 K and 33 000 K in plasmas created in five various discharge conditions using the
low pressure pulsed arc as an optically thin plasma source operated in helium-nitrogen-oxygen gas mixture. Good agreement
was found among our measured line characteristics and their existing calculated values, based on the quasistatic approximation.
Possible influence of the singly ionized oxygen impurity atoms (O II) on the intensity values of the dip between allowed and
forbidden components was found that can explain the disagreement among some existing experimental and calculated line characteristics
data, at higher electron temperatures and densities. On the basis of the observed asymmetry of the 447.1 nm spectral line
profile we have obtained the ion contribution parameter at 1022 m-3 electron density and 8 000 K electron temperature.
Received 20 February 2001 and Received in final form 25 April 2001 相似文献
8.
The results of an investigation of the electromagnetic wave polarization, probing high-temperature laser plasma, as well as
spatial-temporal structure of the magnetic fields, electron density, current density, and electron drift velocity are presented.
To create the plasma, plane massive Al targets were irradiated with the second harmonic of a phoenix Nd laser at intensities
up to 5·1014 W/cm2. It was shown that the magnetooptical Faraday effect is the main mechanism responsible for the changing polarization of the
probing wave. Magnetic fields up to 0.4 MG with electron densities ∼1020 cm−3 were measured. Analysis of the magnetic field spatial distribution showed that the current density achieved the value ∼90
MA/cm2 on the laser axis. The radial structure of the magnetic field testified to the availability of the reversed current in the
laser plasma. The spatial and temporal resolutions in these experiments were equaled to ∼5 μsec and ∼50 psec, respectively.
Translated from Preprint No. 35 of the Lebedev Physics Institute, Moscow, 1993. 相似文献
9.
In depth fusion flame spreading with a deuterium-tritium plane fuel density profile for plasma block ignition
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B. Malekynia S. S. Razavipour 《中国物理 B》2012,(12):317-321
<正>Solid-state fuel ignition was given by Chu and Bobin according to the hydrodynamic theory at x = 0 qualitatively. A high threshold energy flux density,i.e.,E* = 4.3×1012 J/m2,has been reached.Recently,fast ignition by employing clean petawatt-picosecond laser pulses was performed.The anomalous phenomena were observed to be based on suppression of prepulses.The accelerated plasma block was used to ignite deuterium-tritium fuel at solid-state density. The detailed analysis of the thermonuclear wave propagation was investigated.Also the fusion conditions at x≠0 layers were clarified by exactly solving hydrodynamic equations for plasma block ignition.In this paper,the applied physical mechanisms are determined for nonlinear force laser driven plasma blocks,thermonuclear reaction,heat transfer, electron-ion equilibration,stopping power of alpha particles,bremsstrahlung,expansion,density dependence,and fluid dynamics.New ignition conditions may be obtained by using temperature equations,including the density profile that is obtained by the continuity equation and expansion velocity.The density is only a function of x and independent of time.The ignition energy flux density,Et*,for the x≠0 layers is 1.95×1012 J/m2.Thus threshold ignition energy in comparison with that at x = 0 layers would be reduced to less than 50 percent. 相似文献
10.
A Nd:YAG laser with 109 W/cm 2 pulse intensity, operating at 532 nm wavelength, is used to ablate Ta and Cu targets placed in vacuum. The ablation process generates a plasma in front of the target surface, which expands along the normal to target surface. The ion and electron emissions from the plasma were measured by Faraday cups placed at different angles with respect to the normal to target surface. In the range of laser intensities from 107 to 109 W/cm2, the fast electron yield is lower than the ion yield and it increases at higher laser intensities. The ablation threshold, the emission yield, the ion and electron average energies and the plasma ion and electron temperatures were measured for ion and fast electron streams. 相似文献
11.
R. Mavaddat 《Applied Physics A: Materials Science & Processing》1980,21(3):271-277
The recent availability of focussed laser beams with flux densities well in excess of 1015 watts/cm2 at 1.06 μm has led to experimental investigations of direct interaction between intense electromagnetic fields and charged
particles. In this paper the relevant hydrodynamic two-fluid mode equations for a singly ionized tenuous plasma eveloped by
an intense spatially varying electromagnetic field at the focus of a pulsed laser beam is solved by computer simulations for
a cylindrically symmetric geometry. Radial, axial and temporal variations of electron and ion densities are given for different
laser intensities and particle number densities. Fluctuations in electron density are found due to the bulk oscillation of
electrons relative to what is essentially a static array of massive ions. The possibility of generating intense electromagnetic
fields devoid of charged particles is discussed. 相似文献
12.
E.-K. Park H.-J. Woo K.-S. Chung H. Tanaka S. Kajita N. Ohno 《Current Applied Physics》2012,12(6):1497-1502
Axial and azimuthal flow velocities have been measured in a linear plasma device called NAGDIS-II (NAGoya DIvertor Simulator-II), along with plasma density and electron temperature, using a vector Mach probe composed of two Mach probes, one of which is for the axial flow, and the other is for the azimuthal flow. To study the effect of neutral pressure on the deduction of the Mach numbers, the ratio of upstream to downstream currents are measured by changing the neutral pressure for the deduction of flow velocities. Helium plasma was generated with pressure of 2–35 mTorr. Since the ion gyro-radius at the magnetic flux of 300 G is larger than the probe size, an unmagnetized collisionless Mach probe theory was used for the deduction of Mach numbers and their variations. In order to check the range of collisionality, plasma density (ne = 1010–1011 cm?3) and electron temperature (Te = 2–9 eV) are measured by a single electric probe using a conventional collisionless probe theory. Variations of Mach number, electron temperature and plasma density with collisionless models are to be compared with those using collisional models for different pressures where ionization and ion-neutral collision are included. Mach numbers by the collisionless model are found to be overestimated by 120% for the maximum difference even in weakly collisional plasmas. A clear flow reversal exists in the axial direction with higher pressure plasma, even in the linear machine. Azimuthal flows are also measured simultaneously along with axial flows, yet they seem to be very small in the present cold ion plasma (Ti/Te << 1). 相似文献
13.
Junichi Noma Hiroya Abe Takehito Kikuchi Makio Naito 《Journal of magnetism and magnetic materials》2010,322(13):1868-1871
Spherical crystalline Fe nanoparticles, ∼100 nm in diameter, were synthesized under Ar-50% H2 arc-plasma. These nanoparticles were dispersed in silicone oil after silane treatment on as-grown thin oxide layer (∼2 nm) to make their surfaces hydrophobic. The resulting Fe nanoparticles exhibited a high saturation magnetization of ∼190 emu/g at room temperature. The static magnetorheological behavior was measured for the colloidal dispersion (solid concentration: 15 vol%) at room temperature under magnetic flux densities of 0-0.3 T, using a parallel-plate-type commercial rheometer. The yield stress continuously increased with magnetic flux density, demonstrating the Bingham plastic behavior. Moreover, subjecting the sample to a magnetic flux density of 0.3 T increased the yield stress by ∼102. Additionally, the colloidal dispersion exhibited good stability against sedimentation. 相似文献
14.
From measurements of the Hα and Hβ spectral line profiles in a plasma, a method is developed which allows to separate the contributions of Doppler and Stark broadening. This method is superior to the deconvolution of Voigt profiles, in particular, when the lines are of low intensity. The electron density in the plasma can be calculated from the Stark broadening. An example is the low pressure (p ≈ 1 hPa) arc discharge of argon ion lasers which is characteristised by electron densities of approximately 1014 cm?3 at heavy particle temperatures of about 104 K. These plasma parameters lead to a broadening of the Balmer Hα and Hβ spectral lines of hydrogen, which has a low concentration within the discharge area. The spectral lines are broadened due to the electron density dependent Stark effect and the temperature responsive Doppler effect. The results are consistent with predictions of the argon ion laser modelling. 相似文献
15.
The generation, detection and measurement of laser-induced carbon plasma ions and their implantation effects on brass substrate have been investigated. Thomson parabola technique was employed to measure the energy and flux of carbon ions. The magnetic field of strength 80?mT was applied on the graphite plasma plume to provide an appropriate trajectory to the generated ions. The energy of carbon ions is 678?KeV for laser fluence of 5.1?J/cm2 which was kept constant for all exposures. The flux of ions varies from 32?×?1011 to 72?×?1014?ions/cm2 for varying numbers of laser pulses from 3000 to 12,000. In order to explore the ion irradiation effects on brass, four brass substrates were irradiated by carbon ions of different flux. Scanning electron microscope (SEM) and X-ray diffractometer (XRD) are used to analyze the surface morphology and crystallographic structure of ion-implanted brass, respectively. SEM analysis reveals the formation and growth of nano-/micro-sized cavities, pores and pits for the various ion flux for varying numbers of laser pulses from 3000 to 12,000. By increasing ion flux by increasing the number of pulses up to 9000 shots, the dendritic structures initiate to grow along with cavities and pores. At the maximum ion flux for 12,000 shots, the unequiaxed dendritic structures become distinct and the distance between the dendrites is decreased, whereas cavities, pores and pits are completely finished. The XRD analysis reveals that a new phase of ZnC (0012) is formed in the brass substrate after ion implantation. Universal tensile testing machine and Vickers microhardness tester are used to explore the yield stress, ultimate tensile strength and microhardness of ion-implanted brass substrate. The mechanical properties monotonically increase by increasing the ion flux. Variations in mechanical properties are correlated with surface and structural modifications of brass. 相似文献
16.
《Journal of Quantitative Spectroscopy & Radiative Transfer》1986,36(4):373-383
Using a time-dependent approach, a collisional-radiative model is developed for an oxygen plasma. Effective recombination and ionization coefficients are calculated for two specific cases, optically thin and optically thick in bound-bound u.v. radiation. The steady-state population densities for neutral and ionic states are presented in terms of their deviations from Saha equilibrium predictions. These results show the approach of the plasma to a state of local thermodynamic equilibrium (LTE) as a function of electron temperature and density. The computations are for temperatures between 1.0 and 3.0 eV and electron densities between 1016 and 1019 cm-3. 相似文献
17.
Electromagnetic properties of YBaCuO superconductor were measured on applying an external magnetic field to study non-volatile magnetic effect. The voltage increases with increase in applied magnetic flux, but it becomes constant at about 10−2 T. The appearance of the voltage is ascribed to the trapping of magnetic flux. By changing the density of external magnetic flux, changes in inductance of a coil in which a superconducting bar inserted were also measured. The results showed that the filament model was valid to explain the mechanism of the occurrence of a voltage in superconducting sample. It was concluded that the electromagnetic properties arose from the interaction between the trapped magnetic flux and weak link of the filament formed in the superconducting bulk. 相似文献
18.
The properties of an extensive reflex discharge of large power with one heated and one cold cathode in a magnetic field of 10 to 1500 Gauss were measured. At a neutral hydrogen pressure of 10–4 to 10–3 torr a plasma column was obtained which was 100 cm long, 10 cm in diameter and had a density greater than 10–11 cm–3. The dependence of the radial profile of the potential in the plasma was measured by a heated probe, and the temperature and electron density by Langmuir probes calibrated by a microwave interferometer.The dependence of the origin of low-frequency rotational instability on the parameters of the discharge was studied and the measured critical magnetic field was compared with theory. Apart from this low-frequency instability, intensive oscillations were also found in the discharge current in a frequency band up to 30 MHz, and the dependence of their spectrum on the magnetic field was measured. 相似文献
19.
The compression of an electron-hole plasma, caused by a ?-pinch in extrinsic InSb of 140 K, was investigated by measuring the absorption of 10·6 μm radiation and the change of the magnetic flux in the sample. A plasma density of 5 × 1015 cm?3 was hereby found. The temporal development of the plasma density indicates that the electrons and holes resulted from impact ionization in the electric field when the magnetic field was low. Since the electric field is highest at the sample surface, the ionization was limited to the outer region of the sample and the plasma was transmitted to the inner sample volume by the ?-pinch. 相似文献
20.
Andrej Kharchenko Mikhail Lukashevich Vladimir Popok Rustam Khaibullin Valerij Valeev Valerij Bazarov Oleg Petracic Andreas Wieck Vladimir Odzhaev 《Particle & Particle Systems Characterization》2013,30(2):180-184
Nanoparticles (NPs) of cobalt are synthesized in shallow layers of polyimide using 40 keV implantation of Co+ ions with a few different fluences at various ion current densities. Nucleation of individual NPs at low fluencies and their percolation at high fluencies are crucial processes governing the electrical and magnetic properties of the metal/polymer nanocomposites that can be controlled by the implantation regimes. In particular, one can tune the magnetoresistance between negative and positive through appropriate choice of ion fluence and current density. The found non‐monotonous dependence of the magnetoresistance on the applied magnetic field allows suggestion of spin‐dependent domain wall scattering affecting the electron transport. The samples implanted with low fluencies demonstrate superparamagnetic behavior down to very low blocking temperatures. For high fluence (1.25 × 1017 cm−2) the transition to ferromagnetic ordering is observed that is related to the increased magnetic interaction of NPs. 相似文献