共查询到20条相似文献,搜索用时 27 毫秒
1.
S. I. Lashkul V. N. Budnikov A. D. Gurchenko E. Z. Gusakov V. V. Dyachenko L. A. Esipov E. R. Its M. Yu. Kantor D. V. Kouprienko K. M. Novik A. Yu. Popov V. L. Selenin A. Yu. Stepanov V. B. Yermolajev S. V. Shatalin E. O. Vekshina 《Czechoslovak Journal of Physics》2002,52(10):1149-1159
Experiments at the FT-2 tokamak had demonstrated effective plasma LH heating, which was accounted for by both direct absorption
of RF power and plasma transport suppression. The improved core confinement accompanied by Internal Transport Barrier (ITB)
formation was observed. The RF pulse switch off is followed by triggering of LH transition and the External Transport Barrier
(ETB) formation near the last closed flux surface. The present paper is devoted to a much more detailed study of the radial
electric fieldE
r behaviour in the region of ITB and ETB and its influence on the tokamak microturbulence in these regions. The new experimental
data were obtained by spatial spectroscopic technique using additional pulse helium puffing in hydrogen plasma. Simultaneously
microscale plasma oscillations in the frequency band (0.01–2) MHz are observed with local enhanced microwave scattering diagnostics
and by x-mode fluctuation reflectometry. Experiments demonstrate that the improved confinement is associated with the modification
of microturbulence by the shear of theE×B poloidal velocity. This conclusion is also confirmed by the data obtained by Langmuir probes in the edge plasma.
Presented at 5th Workshop “Role of Electric Fields in Plasma Confinement and Exhaust”, Montreux, Switzerland, June 23–24,
2002”.
The study was performed with the support of the Ministry of General and Professional Education of RF (TOO-7.4-2797), INTAS-01-2056
and the RFBR Grants 00-02-16927, 01-02-17926 and 02-02-17684. 相似文献
2.
Chengfu Mu Pengfei Zhuang 《The European Physical Journal C - Particles and Fields》2008,58(2):271-279
We investigate the effect of the restoration of chiral symmetry on the quark potential in a quark–meson plasma by considering
meson exchanges in the two flavor Nambu–Jona-Lasinio model at finite temperature and density. There are two possible oscillations
in the chiral restoration phase; one is the Friedel oscillation due to the sharp quark Fermi surface at high density, and
the other is the Yukawa oscillation driven by the complex meson poles at high temperature. The quark–meson plasma is strongly
coupled in the temperature region 1≤T/T
c≤3, with T
c being the critical temperature of the chiral phase transition. The maximum coupling in this region is located at the phase
transition point. 相似文献
3.
Results of spectroscopic investigations into plasma of a pulse-periodic strontium vapor laser operating in the superradiance
mode on the infrared transition at λ = 6.45 μm are presented. The method of determining the electron temperature and concentration
as well as the gas temperature – T
e
, n
e
, and T
g
– based on measuring the absolute intensities of some SrI and SrII and buffer gas (helium or neon) spectral lines is used.
Time dependences of the line intensities during a current pulse (τ = 150 ns) and near afterglow (up to 3 μs) are obtained
under conditions of non-equilibrium plasma ionization and recombination. The optical system collects radiation from the entire
length of the plasma column by means of separating radial volume zones, includingthe central zone and the zone closer to the
walls, with the monochromator slit. The results obtained allow us not only to calculate T
e
, n
e
, and T
g
values, but also to trace the spatiotemporal plasma evolution. 相似文献
4.
V. M. Egorov Yu. M. Baikov N. F. Kartenko B. T. Melekh Yu. N. Filin 《Physics of the Solid State》1998,40(11):1911-1914
Differential scanning calorimetry was used to study phase transitions (PT) in the perovskite BaCeO3. It is shown that its phase state is determined by a second-order λ transition at T
tr=520–540 K and a first-order δ transition at T
tr=600–670 K. Differences in PT parameters between ceramic and fused BaCeO3 have been established.
Fiz. Tverd. Tela (St. Petersburg) 40, 2109–2112 (November 1998) 相似文献
5.
V. S. Gaviko V. E. Arkhipov A. V. Korolev V. E. Naish Ya. M. Mukovskii 《Physics of the Solid State》1999,41(6):969-973
A study is made of phase transitions in doped La0.9Sr0.1MnO3 compounds using combined x-ray, electrical, and magnetic measurements. Structural phase transitions are observed accompanied
by a change in the cell volume at temperatures of 100–110 K and 300–340 K. These structural changes are found to be related
to different contributions of the rhombic Jahn-Teller Q
2 mode to the formation of the crystal lattice. The structural transition at 100–110 K is accompanied by distinctive magnetic
and electrical properties. The data are analyzed in detail.
Fiz. Tverd. Tela (St. Petersburg) 41, 1064–1069 (June 1999) 相似文献
6.
In a dusty plasma, the non-adiabaticity of the charge variation on a dust grain surface results in an anomalous dissipation.
Analytical investigation shows that this results in a small but finite amplitude dust acoustic (DA) wave propagation which
is described by the Korteweg-de Vries-Burger equation. Results of the numerical investigation of the propagation of large-amplitude
dust acoustic stationary shock wave are presented here using the complete set of non-linear dust fluid equations coupled with
the dust charging equation and Poisson equation. The DA waves are of compressional type showing considerable increase of dust
density, which is of significant importance in astrophysical context as it leads to enhanced gravitational attraction considered
as a viable process for star formation. The DA shock transition to its far downstream amplitude is oscillatory in nature due
to dust charge fluctuations, the oscillation amplitude and shock width depending on the ratioω
pd/Vch and other plasma parameters
Article presented at the International Conference on the Frontiers of Plasma Physics and Technology, 9–14 December 2002, Bangalore,
India. 相似文献
7.
A. G. Rousskikh A. V. Shishlov A. S. Zhigalin V. I. Oreshkin S. A. Chaikovsky R. B. Baksht 《Technical Physics》2010,55(11):1619-1627
The results of the experiments on the formation of a plasma emitter with small spatial dimensions for pulsed radiography in
the soft X-ray spectral range are presented. Emitting hot plasma was formed as a result of compression of the plasma jet by
a current pulse with amplitude I
m
= 215 kA and rise time T
fr = 200 ns. For the jet formation, we used a plasma gun based on the arc discharge (I
m
= 8.5 kA and T
fr = 6 μs) initiated by breakdown over the surface of a dielectric in vacuum. The experiments were carried out with aluminum,
tin, copper, and iron plasma jets. A single emitter, i.e., point Z-pinch (PZ-pinch), was formed when an interelectrode gap of a high current generator of 1.3–1.5 mm was used. The smallest spatial dimensions
of the emitting region were obtained with the use of aluminum and tin. For a tin jet, the diameter of the emitting region
was 7 ± 2 μm and its height was 17 ± 2 μm. The emission pulse duration at half-height was 2–3 ns. The total emission yield
per pulse in the spectral range 1.56–1.90 keV was 30–50 mJ for the aluminum pinch and 10–30 mJ for the tin pinch. The developed
method makes it possible to carry out radiographic examination of microobjects (including biological ones) 1–1000 μm in thickness,
with spatial (10–20 μm) and time (2–3 ns) resolution. 相似文献
8.
V. V. Belyaev A. T. Mayunov G. D. Mikhailov S. N. Razin’kov 《Radiophysics and Quantum Electronics》2000,43(2):115-118
Electromagnetic wave scattering by a horn antenna with a nonlinear Al−Al2O3−Al junction is studied experimentally and theoretically at the third harmonic of the irradiating field for decimeter wavelengths.
The influence of junction nonlinearity on horn antenna detectability is estimated when the latter is observed by a “nonlinear”
radar.
The 5th Central Research Institute of the Ministry of Defense of the Russian Federation, Voronezh, Russia. Translated from
Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 43, No. 2, pp. 126–129, February 2000. 相似文献
9.
A transition of expanded liquid iron to the nonmetallic state under high pressures (30–100 kbar) at high temperatures (of
about 1 eV) is discovered. The result is obtained by direct measurement of the dependence of resistivity on the specific internal
energy and volume. Measurements are taken in the specific volume range from the melting curve to values six times higher than
the normal specific volume V
0 in the solid state. It is shown that iron remains in the metallic state up to a relative volume of V/V
0 = 3–4, at which the resistivity attains a value of about 3–4 μΩ m and becomes almost independent of temperature, while the
conduction electron mean free path decreases to the atomic spacing. For V/V
0 = 4–5, a transition to the nonmetallic state takes place, for which the temperature coefficient of resistance becomes negative
and its absolute value becomes much higher than in the metallic state. 相似文献
10.
M. M. Kirillova I. D. Lobov V. M. Maevskii L. V. Nomerovannaya A. A. Makhnev G. A. Bolotin F. A. Pudonin 《Journal of Experimental and Theoretical Physics》1997,85(5):925-933
The optical and magneto-optical properties of multilayered film samples of the Fe/Cu system prepared by high-frequency sputtering
on an Si(100) substrate are studied by ellipsometry and by measuring the equatorial Kerr effect (the δ
p effect) in the spectral range 0.25–7 μm. The optical characteristics, the plasma frequency ω
p and the relaxation frequency γ
0 of the conduction electrons, and the δ
p effect are found as functions of the modulation period D=12.5–100 Å. Anomalous behavior of the optical and magneto-optical characteristics is discovered in short-period Fe/Cu structures.
The results are discussed within a phenomenological theory of optical and magneto-optical properties for layered structures.
Several factors, such as the indirect exchange interaction between the iron layers, the presence of a transition layer on
the internal boundaries, the possible “magnetizing” of copper, and the formation of an fcc iron phase in the thin layers,
are taken into account in the analysis of the experimental data.
Zh. éksp. Teor. Fiz. 112, 1694–1709 (November 1997) 相似文献
11.
I. O. Bashkin M. V. Nefedova V. G. Tissen E. G. Ponyatovskii 《Physics of the Solid State》1998,40(12):1950-1952
The pressure dependence of the superconducting transition temperature in TiD0.74 has been measured up to 30 GPa in a diamond high-pressure chamber. It is found that the deuteride TiD0.74 becomes a superconductor at pressures corresponding to the transition to the high-pressure ζ phase, with a transition temperature that increases from 4.17 to 4.43 K in the interval P=14–30 GPa. The value extrapolated to atmospheric pressure T
c
(0)=4.0 K is significantly lower than the superconducting transition temperature (T
c
=5.0 K) measured earlier in the metastable state obtained by quenching TiD0.74 under pressure. It is assumed that the significant difference of the extrapolated value from the superconducting transition
temperature in the metastable state after quenching under pressure is caused by a phase transition on the path from the stability
region of the ζ phase under pressure to the region of the metastable state at atmospheric pressure.
Fiz. Tverd. Tela (St. Petersburg) 40, 2153–2155 (December 1998) 相似文献
12.
Z. A. Kazei V. V. Snegirev A. S. Andreenko L. P. Kozeeva 《Journal of Experimental and Theoretical Physics》2011,113(2):245-250
The elastic properties of rare-earth cobaltites RBaCo4O7 (R = Y, Tm-Lu) have been experimentally studied in the temperature range of 80–300 K. The strong softening of the Young modulus
ΔE(T)/E
0 ≈ −(0.1–0.2) of cobaltites with Lu and Yb ions has been revealed, which is due to the instability of the crystal structure
upon cooling and is accompanied by an inverse jump at the second-order structural phase transition. The softening of the Young
modulus and the jump at the phase transition decrease by an order of magnitude and the transition temperature T
s and hysteresis ΔT
s increase from a compound with Lu to that with Tm. A large softening of the Young modulus at the structural transition in
Lu- and Yb cobaltites indicates that the corresponding elastic constant goes to zero, whereas this constant in Tm cobaltite
is not a “soft” mode of the phase transition. It has been found that the structural phase transition in Lu- and Yb cobaltites
is accompanied by a large absorption maximum at the phase transition point and an additional maximum in the low-temperature
phase and absorption anomalies in Tm cobaltite is an order of magnitude smaller. 相似文献
13.
A series of polymer nanocomposite films based on intercalation of (PAN)8LiCF3SO3 into the nanometric clay channels of an organomodified clay has been prepared using the standard solution-casting technique.
The role of organoclay concentration on polymer–ion interaction, ion–ion interaction, and ion–clay interaction in clay-based
nanocomposite films has been analyzed using Fourier transform infrared (FTIR) analysis. Substantial ion dissociation is observed
even at a very low clay loading (1–2 wt.%) in the nanocomposites. FTIR results suggest the presence of both uncoordinated
CF3SO3
− (free-anions) and ion pairs in the nanocomposite evidenced by changes in CF3SO3
− symmetry from C3ν to Cs and marked asymmetry in the profile of degenerate δd(CF3
−) mode. The experimental results suggest a direct correlation of clay-assisted ion dissociation process with variation in
conductivity (σ
dc) and glass transition temperature (T
g) as a function of clay concentration. A model has been proposed to explain the observed correlation on the basis of polymer–ion–clay
interaction. The proposed scheme of ion transport mechanism appears to be consistent with the experimental observation. 相似文献
14.
The crystallization and glass transition kinetics using differential scanning calorimetry (DSC) in 50AgI–33.33Ag2O–16.67[(V2O5)1−x
–(MoO3)
x
] superionic glassy system is discussed. Thermal stability of glass, studied using various criteria, does not vary significantly
with glass former variation. However, the activation energies for structural relaxation (E
s) at glass transition temperature and crystallization (E
c) obtained using Moynihan and Kissinger, Matusita-Sakka formulations found to exhibit interesting trends with MoO3 substitution in the glass matrix. It is noticed that the electrical conductivity (σ)–temperature (T) cycles obtained at a typical heating rate of 1 °C/min do exhibit significant thermal events. The conductivity after first
heating cycle at room temperature is found to be increasing with MoO3 content and maximum for x = 0.3 (~10−3 Ω−1 cm−1 at 30 °C) which is comparable to that of the host 50AgI–33.33Ag2O–16.67V2O5 glassy system. The parameters obtained from σ–T plots and DSC scans do complement each other in a particular range of composition. 相似文献
15.
Leonid G. Eliseev Alexander V. Melnikov Ludmila I. Krupnik HIBP Team 《Czechoslovak Journal of Physics》2000,50(12):1413-1420
Heavy Ion Beam Probe diagnostics was used to study plasma potential and density in the regimes with improvement in confinement
on the T-10 tokamak. Time-spatial potential distribution was analyzed during the formation of transport barriers. The time
evolution of the potential profile shows simultaneous formation of the internal negative potential well and external layer
with strong Er, during the simultaneous formation of the internal and external transport barriers. The time history of the
plasma potential in the inner region (0.6<ρ<1) shows its clear correlation with theD
α intensity.
Presented at the Workshop on the Role of Electric Fields in Plasma Confinement and Exhaust, Budapest, 18–19 June, 2000.
This work was supported by Russian Basic Research Foundation, Grant No. 99-02-18457. 相似文献
16.
N. E. Sluchanko A. N. Azarevich A. V. Bogach S. Yu. Gavrilkin V. V. Glushkov S. V. Demishev A. V. Dukhnenko A. B. Lyashchenko K. V. Mitsen V. B. Filipov 《JETP Letters》2011,94(8):642-646
The specific heat of the ZrB12 compound in the normal and superconducting states (T
C
≈ 6 K) has been studied in the 1.9–7 K temperature range for high-quality single crystals with different relative contents
of boron isotopes. For Zr10B12, ZrnatB12, and Zr11B12 dodecaborides, the electron density of states and the electronphonon coupling constant, λe-ph ∼ 0.4, are found. The dependence of the thermodynamic and upper critical fields, as well as of the Ginzburg-Landau parameter
(κ = 0.8–1.14) on temperature and isotope composition is determined. The results suggest the existence of the magnetic field
induced phase transition at T* = 4–5 K, which is not related to the transition from type-I to type-II superconductivity. The possibilities of the existence
of two-gap superconductivity and a structural phase transition at T* in zirconium dodecaboride are discussed. 相似文献
17.
V. A. Moshnikov A. V. Moshnikov A. I. Rumyantseva S. A. Nemov R. V. Parfen’ev A. V. Chernyaev 《Physics of the Solid State》1999,41(4):550-555
A reliable technique of local chemical characterization of multicomponent semiconductor solid solutions has been developed,
and the possibility of its application to the SnTe-SnSe quaternary solid solutions doped with 16 at.% In verified. The behavior
of the electrical resistivity of samples of these solid solutions at low temperatures, 0.4–4.2 K, has been studied. The critical
temperature T
c and the second critical magnetic field H
c2 of the superconducting transition and their dependences on the solid-solution composition have been determined. The superconducting
transition at T
c≈2–3 K is due to hole filling of the In-impurity resonance states, and the observed variation of the superconducting transition
parameters with increasing Se content in the solid solution is related to the extrema in the valence band and the In band
of resonance states shifting with respect to one another.
Fiz. Tverd. Tela (St. Petersburg) 41, 612–617 (April 1999) 相似文献
18.
E.?P.?Smirnova A.?V.?Sotnikov H.?Schmidt N.?V.?Za?tseva M.?Weihnacht 《Physics of the Solid State》2009,51(12):2492-2496
The dielectric and acoustic properties of (1 − x)SrTiO3-xBiFeO3 (0 ≤ x ≤ 0.04) solid solutions have been studied in the temperature range 10–300 K. The polar state exhibiting permittivity dispersion
and dielectric hysteresis loops has been revealed at temperatures of 40–100 K. At 20–40 K, we have observed one more dielectric
relaxation, which is not associated with the polar state and vanishes at a concentration of the second solid-solution component
x = 0.04. The antiferrodistorsive transition has been found to vary with increasing concentration x. At temperatures below the antiferrodistorsive transition point, the polar (relaxor) state has been shown to persist in all
the measured solid solutions. 相似文献
19.
Y. Gangrsky K. Marinova S. Zemlyanoi M. Avgoulea J. Billowes P. Campbell B. Cheal B. Tordoff M. Bissell D. H. Forest M. Gardner G. Tungate J. Huikari H. Penttilä J. Äystö 《Hyperfine Interactions》2006,171(1-3):209-215
Collinear laser spectroscopy experiments on the ScII transition 3d4s
3D2→3d4p
3F3 at λ ≈ 363.1 nm were performed on the 42–46Sc isotopic chain using an ion guide isotope separator with a cooler–buncher. Isotope and isomer shifts and hyperfine structures
of five ground states and two isomers were measured. Preliminary results on the nuclear moments and charge radii changes deduced
from these measurements are reported. 相似文献
20.
V. Antoni R. Bartiromo L. Carraro D. Desideri E. Martines M. E. Puiatti F. Sattin P. Scarin G. Serianni M. Spolaore L. Tramontin M. Valisa B. Zaniol 《Czechoslovak Journal of Physics》2000,50(12):1387-1396
The experimental determination of the radial electric fieldE
r and the associatedE ×B drift velocity at the edge of RFX is presented and possible mechanisms responsible for its generation are discussed.E
r measurements by means of an array of Langmuir probes and those deduced from Doppler spectroscopy of impurity lines agree
fairly well. In particular the rotation velocity of the plasma edge has been determined from the Doppler shift of a C III
emission line. The observation of other ions characterised by different radial positions, such as B IV and C V, has allowed
an estimate of the velocity shear. Typical values of plasma rotation at the edge are around 10 km/s while the velocity shear
is of the order of (105−106)s−1 in the spontaneous layer, a few cm thick, usually observed in standard discharges. Plasma rotation has been artificially
modified by both positive and negative edge biasing and the associated increase or decrease of the fluid velocity is well
in agreement with the radial electric field change. The modification ofE
r during edge biasing and Pulsed Poloidal Current Drive (PPCD) are also reported and interpreted within a momentum balance
model. Analytical and self-consistent Monte Carlo models at the plasma edge suggest that impurities have a relevant role in
the generation of the radial electric field, due to their relatively large Larmor radius.
Presented at the Workshop on Role of Electric Fields in Plasma Confinement and Exhaust, Budapest, 18–19 June 2000. 相似文献