共查询到20条相似文献,搜索用时 31 毫秒
1.
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
2.
J. Janča 《Czechoslovak Journal of Physics》1967,17(9):761-772
By methods of spectral diagnostics, the temperature of neutral gas and the electron temperature and density have been determined in the channel of a unipolar high-frequency discharge excited at very high pressures. In nitrogen the h.f. discharge was excited at pressures of 1–5 atm, in argon at pressures of 1–12 atm. In the discharge excited in argon, the electron temperature does not change with increasing pressure and isT
e
=(6–7)×103 °K; the electron density increases with increasing pressure. It can be demonstrated that the electron velocity distribution is given by a Maxwellian distribution function although the plasma of a unipolar high-frequency discharge is non-isothermal (T
e
–T
n
5×103 °K).In conclusion, the author thanks Prof. Dr. V. Truneek for stimulating remarks and his kind interest in this work. 相似文献
3.
S. I. Nanobashvili Z. R. Beria L. R. Gakheladze G. E. Gogiashvili 《Czechoslovak Journal of Physics》1996,46(9):839-850
A stationary UHF plasma source, its characteristics and possibility of filling open magnetic trap with plasma injected from it have been described. Plasma is created in the source at frequency of 2400 MHz (supplied power is up to 150 W) in the electron cyclotron resonance (ECR) regime under working gas pressure 10–5–10–2 Torr. By changing discharge conditions one can change the injected plasma density from 109 to 1012 cm–3, at the temperatureT
e=2–10 eV. The possibility of efficient plasma injection from the source into the open magnetic trap of various configurations is shown experimentally. Plasma characteristics in the trap are presented under various experimental conditions. It is established that plasma parameters can be easily changed in the trap. 相似文献
4.
We have obtained population inversion of a system of polarized (P=80%) electron spins in a solid during a very fast (dB
z
dt=4·105
T·s
–1) reversal of the external magnetic field. The electrons were trapped at oxygen vacancies in CaO single crystals. This method, whch does not exploit any high frequency electromagnetic field, has been for the first time successfully used to achieve an inverted state of electron spins in a solid. The negative temperature of an electron spin ensembleT=–23 mK has been obtained. 相似文献
5.
Yu. A. Bykovskii I. A. Garifullin V. F. Elesin V. I. Kadushkin E. A. Protasov A. G. Rodionov 《Russian Physics Journal》1972,15(2):230-233
Investigations of the Shubnikov-de Haas oscillation of the transverse magnetoresistance due to the magnitude of the electric field in n-type InSb with 5 · 1015, 3 · 1016 cm–3 concentrations at a 4.2 °K temperature are carried out herein. A method is proposed to determine the electron temperature Te; dependences of Te on the electric and magnetic fields in the sample are obtained for a transversely oriented magnetic field. The relaxation time of the electron energy is estimated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 96–100, February, 1972. 相似文献
6.
The plasma flow velocity in the Plasma Generator PSI‐2 has been investigated by using of Mach probe. PSI‐2 is a stationary high‐current arc discharge in which the quasi‐neutral plasma expands along the magnetic field lines. The low‐temperature (Te < 20 eV), medium density (ne ∼ 1018— 1019 m—3 ) plasma in the discharge is similar to the plasma in the divertor region of tokamaks. From the ratio of ion saturation currents collected from opposite sides of the probe the flow velocities (Mach numbers) in argon and hydrogen discharges are obtained. 相似文献
7.
The study deals with the effect of an applied transverse magnetic field on the dynamics and parameters of the focused and expanded plasma in a coaxial discharge. The experimental results were found with a 3 kJ Plasma focus device of a Mather geometry. The discharge takes place in hydrogen gas with base pressure of 0.5 Torr. The experiments are conducted with a 10 kV bank voltage, which corresponds to 100 kA peak discharge current with rise time 8 μs. Helmholtz magnetic coils are placed outside the expansions chamber to produce a transverse magnetic field with intensity 280 G perpendicular to the plasma expanded from the coaxial electrodes. The investigations have shown that the plasma flow along the expansion chamber axis is restricted when applying the externally transverse magnetic field and the maximum axial velocity of the expanded plasma is decreased by 33%. X-ray probe has been used to measure the focused plasma electron temperature (Te). The experimental results and the calculations showed that Te is decreased from 2.2 keV to 800 eV with the application of a transverse magnetic field. The expanded plasma electron temperature and density have been measured by an electric double probe, the results cleared that the expanded plasma electron temperature is decreased by 2.6 times while its density is increased by 9 times, when a transverse magnetic field is applied. 相似文献
8.
By observing the primary electron trajectories and studying experimentally the equilibrium of an argon plasma in the pressure range 0.8 × 10?4 – 8 × 10?4 torr, we show that the main effect of the surrounding magnetic wall is not the confinement of the plasma but the confinement of the primary electrons in the discharge. 相似文献
9.
The manner of preparation of superconducting 25% wt Nb–75% wt Zr wires is described. Short samples of these wires were measured in static magnetic fields up to 80·5 kG and the authors describe the method of these measurements. The paper gives the results of measuring the critical current density dependence on the external perpendicular magnetic field for both cold-worked wires with different deformations and heat-treated wires. The dependence of the critical current density on the heat treatment temperature after wire deformation for different magnetic fields was obtained. The optimum heat treatment temperature (vacuum better than 10–3 torr, 1 hour) is 450–600C for magnetic fields 0–80·5 kG. The values ofi
c of these wires in magnetic fields up to 60 kG are the same or higher than those of 75% Nb-25% Zr wires, and in fields above 60 kG they are much higher. 相似文献
10.
Yu. E. Kamenev V. K. Kiseliov Ye. M. Kuleshov B. N. Knyaz''kov V K. Kononenko P. K. Nesterov M. S. Yanovsky 《International Journal of Infrared and Millimeter Waves》1998,19(6):835-848
The testing results of a homodyne 0.195-mm laser interferometer-polarimeter based on quasioptical components are presented. The interferometer-polarimeter matched to the multichannel interferometer of a Tokamak-15 machine admits of simultaneous measurements of the plasma electron density and poloidal magnetic field in one of the seven vertical-probing channels without any disturbance in the others. The achieved responce threshold of the electron density is 3.4·1011 cm–3, the polarization resolution and the phase difference measurement error are no worse than 0,10 and ±40, respectively. 相似文献
11.
An investigation was made of the process of contraction of a nanosecond volume discharge in air with a homogeneous field distribution and a current density 500 A/cm2 when the gap was 0.7 cm and the pressure 76 torr. It was found that the appearance of a cathode spot in this volume discharge resulted in an effective contraction of the current into a spot and formation of a diffuse channel. A high-conductivity channel emerging from the cathode spot appeared when the current density in the diffusion channel above this spot reached (1–3)·105 A/cm2.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 16–18, January, 1981. 相似文献
12.
Results of experiments on the investigation of a plasma rotating in crossed electric and magnetic fields are presented. The radial electron concentration distributions in a nitrogen plasma at pressures varying from 8·10–2 to 3·10–1 mm Hg are obtained with the help of a 3.39 m laser interferometer. The effect of the magnitude of the magnetic field on the form of the radial distribution is determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 72–75, January, 1982. 相似文献
13.
Radiofrequency power up to 40 kW injected into the vacuum chamber of the CASTOR tokamak by a multijunction grill was used for plasma formation during the ramp-up phase of the toroidal magnetic field. When electron cyclotron resonance (ECR) appears inside the tokamak chamber for a given pumping frequency (f=1·25 GHz) a plasma with a density greater than 2×1018 m–3 and temperatureTine=10 ÷ 40 eV is produced. The plasma is sustained at some lower value of the density during the whole RF pulse. Simultaneously, a toroidal current up to 0·2 kA is generated. The energy confinement time is estimated to be about 30 s during the ECR breakdown.It is a pleasure to acknowledge very useful discussions with Dr. R. Klíma. 相似文献
14.
S. I. Nanobashvili Z. R. Beria L. R. Gakheladze G. V. Gelashvili G. E. Gogiashvili M. O. Mdivnishvili I. S. Nanobashvili G. I. Rostomashvili 《Czechoslovak Journal of Physics》1999,49(6):999-1004
The properties of plasma injected into an open magnetic trap of uniform field from an independent UHF source have been investigated.
Plasma is created in the UHF source at the frequency of 2400 MHz (power input 150 W) in the electron cyclotron resonance (ECR)
regime at the pressure of neutral argon (10−5−10−2) torr. It is established that a rather quiescent target plasma with controlled density within the range of (2 × 108−2 × 1012) cm−3 and temperature 2–3eV is accumulated in the trap. It turned out that plasma lifetime in the trap is determined by a classical
mechanism of particle escape at the expense of collisions, at fixed value of magnetic field in the trap it practically is
not changed with the variation of neutral gas pressure and reaches the value ≈ 4×10−3 s at the magnetic field strength in the trap equal 1600 Oe. 相似文献
15.
J. Kramář 《Czechoslovak Journal of Physics》1965,15(3):190-200
This article deals with the calculation of the influence of the magnetic field upon the electric current of a thermionic converter presupposing the approach to conditions in a low-pressure cesium converter. The distribution of the starting velocities of the emitted electrons is considered firstly as independent of the angle from the perpendicular to the emitter plane, and secondly according to the cosine law.The magnetic field effect from the converter current is calculated and compared with the calculations in the papers by Schock [1] and Block [2]; the effect of the external magnetic field is verified by measurements on a solar thermionic converter prototype.Symbols
F=I/I
0
factor of current reduction from magnetic field effect
-
¯F
value of factorF (when the magnetic field is not constant)
-
I [A/m2]
density of collector current (real current influenced by magnetic field)
-
I
0 [A/m2]
theoretical density of collector current (in ideal case equals electron emission current)
-
T
e
[°K]
electron gas temperature; assumed equal to emitter temperatureT
E
[°K]
-
B[Wb/m2]
magnetic induction (field)
-
D[m]
distance from emitter to collector
-
R[m]
radius of electrodes, emitter and collector
-
r[m]
variable radius in the limits 0 toR
-
V [m/s]
random velocity of electron
-
v
xz
[m/s]
component of the vectorV inx-z plane
-
v
m
=2kT
E
/m
most probable velocity in the velocity distribution according to Maxwell and Boltzmann
-
w-v
xz
/v
m
relatively expressed electron velocityv
xz
-
the angle of any vectorV
-
[m]
radius of circular electron path
-
n [m–3]
number (density) of electrons with certain value of random velocity
-
n
0 [m–3]
total electron number (density)
-
n
1 [m–3]
number of electrons returned to emitter by means of magnetic field
-
N
0 [m–2s–1]
total flow of thermionic electrons emitted from a unit surface
-
N
1 [m–2s–1]
partial flow of electrons returned to emitter
-
P=N
1/N0
relatively expressed flow of electrons returned to emitter (whenB = const.)
-
¯P
mean value ofP (whenB const.)
-
F
cos,
,P
cos,
values asF,¯F,P,¯P in case of velocity distribution according to cosine law
-
m=9·107×10–31 [gk]
electron mass
-
e=1·60×10–19 [C]
electron charge
-
k×1·38×10–23 [J/grad]
Boltzmann's constant
-
0
1·257×10–6 [H/Vs] permeability of vacuum 相似文献
16.
Ryuiti Ikee Haruo Takeyama 《Journal of Quantitative Spectroscopy & Radiative Transfer》1975,15(6):543-547
The brush cathode helium discharge in the magnetic field has been operated stably at discharge currents larger than those without magnetic field. The diameter of the plasma column has been determined by the configuration of the magnetic field. The measurements of the spectral intensities of the recombination continuum followed by the 23S-n3P series reveals that the electron density is 1·8 × 1013 cm-3 and the electron temperature is 0·17 eV at a discharge current of 500 mA and a pressure of 0·9 torr for a magnetic flux density of 1·3 kG. The principal quantum number for line merging is 20. 相似文献
17.
Production of YBa2Cu3O7−x superconducting thin films by pulsed pseudospark electron beam evaporation
H. P. Schölch P. Fickenscher T. Redel M. Stetter G. Saemann-Ischenko W. Benker W. Hartmann K. Frank J. Christiansen 《Applied Physics A: Materials Science & Processing》1989,48(4):397-400
Thin-film superconducting YBa2Cu3O7–x layers have been produced in a single-step process by pulsed electron beam evaporation from a stoichiometric 1-2-3 target. The films were produced at the 100 surface of SrTiO3 substrates heated to a temperature of approximately 1000 K in a pure oxygen atmosphere of about 10 Pa total pressure. After deposition the films were cooled in situ within 20 minutes to ambient temperature. At present, the films are polycrystalline and show a Tc,zero of 83 K with a transition width of 3–5 K. Critical current densities of 7·104 A/cm2 at 4.2 K and zero magnetic field have been achieved. The pulsed electron beams used in these experiments are produced by a pseudospark discharge; the estimated energy density deposited at the target surface by the electron beam is of the order of 4 J/cm2. 相似文献
18.
Thermal cycling of thin foil samples is used to measure nuclear spin lattice relaxation of dilute58Co and60Co in iron at polarizing fields up to 1.3 T. The relaxation rates for the two isotopes differ by a factor of 7.1; the good agreement between the high field values for 2
C
2, (2.93±0.15)·1015 K·s–1·T–2 (58Co) and (3.01±0.06)·1015K·s–1·T–2 (60Co) verifies the reliability of the experimental method. An enhancement factor model is introduced and shown to give an excellent reproduction of the observed field dependence of the relaxation. 相似文献
19.
Two surface wave plasma columns, generated by microwave power in argon at gas pressures of 0.05 torr to 330 torr, interact in the same discharge tube to form standing surface waves. Radial electric field Er and azimuthal magnetic field H? outside the discharge tube are measured to be 90° out of phase with respect to axial position and to decay exponentially with radial distance from the tube axis. Maximum light emission occurs at the position of maximum H?, and minimum Er. Electron temperature and density are measured at low pressures with double probes inserted into the plasma at a null of Er. Measured electron densities compare well with those predicted by Gould-Trivelpiece (GT) surface wave theory. Measured electron temperatures are the same order of magnitude as temperatures predicted by positive column theory. 相似文献
20.
Horst G. Müller K. Krien U. Pütz F. Reuschenbach R. Trzcinski K. Freitag 《Zeitschrift für Physik B Condensed Matter》1979,32(3):315-318
By implantation of181Hf ions radiation damage is produced in platinum. Subsequent annealing of the samples leads to the trapping of a unique defect at the probe atoms. The temperature dependence of the resulting electric field gradient eq(T) is measured by use of the TDPAC-method. Assuming a relation eq(T)=eq(0)·(1–B·T
3/2) one findsB=(1.9±0.7)×10–6 K–3/2. This low value is of the same magnitude as the corresponding values for111Cd in various locally distorted cubic metals. 相似文献