共查询到20条相似文献,搜索用时 31 毫秒
1.
Generation of runaway electrons and X-ray radiation in helium and air under the action of a pulsed-periodic discharge in a nonuniform electric field is studied. Positive and negative voltage pulses with a repetition rate of up to 1 kHz, a duration on the order of 1 ns, and an incident wave amplitude of 12.5 kV are applied to a needle-plane gap. For both polarities of the main voltage pulse and a helium pressure from several Torr to several tens of Torr, the arrival of negative reflected voltage pulses at the gap is shown to be accompanied by an electron beam generation. X-ray radiation is detected in a wide range of pressure, including under normal pressure of helium and air. 相似文献
2.
A. R. Sorokin 《Technical Physics》2009,54(3):372-379
This work pursues investigations into the discharge with a cathode plasma in a cavity one wall of which is an insulating plate
with a hole D in diameter (the cavity is 0.5 or 1.5 mm wide). This discharge is thoroughly analyzed in comparison with the high-voltage
hollow-cathode discharge. Owing to the reduced emission of electrons from the cathode plasma, the discharge becomes more stable
against transition to the low-voltage form, as a result of which an electron beam can be generated under higher gas pressures.
Such a beam formed at the entrance to the cavity is used as an auxiliary one that propagates over the remaining (flat) surface
of the cathode and adds to the gas ionization. Accordingly, the beam current from the main discharge to the anode rises (high-current
regime). Wide-aperture (D = 22 mm) ≈1-μs-long pulsed beams with a current an order of magnitude higher than the total current of the equivalent anomalous
discharge are obtained. Experiments are carried out at a helium pressure to 20 Torr and a voltage from 1 to 20 kV. 相似文献
3.
E. H. Baksht A. G. Burachenko M. V. Erofeev I. D. Kostyrya M. I. Lomaev D. V. Rybka V. F. Tarasenko 《Technical Physics》2008,53(6):804-807
The effect of a transverse magnetic field (0.080 and 0.016 T) on generation of an electron beam in the gas-filled diode is
experimentally investigated. It is shown that, at voltage U = 25 kV across the diode and a low helium pressure (45 Torr), the transverse magnetic field influences the beam current amplitude
behind a foil and its distribution over the foil cross section. At elevated pressures and under the conditions of ultrashort
avalanche electron beam formation in helium, nitrogen, and air, the transverse magnetic field (0.080 and 0.016 T) has a minor
effect on the amplitude and duration of the beam behind the foil. It is established that, when the voltage of the pulse generator
reaches several hundreds of kilovolts, some runaway electrons (including the electrons from the discharge plasma near the
cathode) are incident on the side walls of the diode. 相似文献
4.
The characteristics of a discharge and radiation in nitrogen and argon under pressures of 10–760 Torr and the discharge formation without pre-ionization of the gap from an auxiliary source are considered. A peak is detected on the pressure dependence of the radiation power of the second positive system of nitrogen for E 0/p ~ 270 V/cm Torr and nitrogen pressure p ~ 70 Torr. In the pressure range 10–760 Torr and for a voltage pulse leading front duration of ~ 10 ns, an electron beam is formed behind the grid anode with various half-amplitude pulse durations. It is shown that, under the given conditions, the electron beam is formed at the voltage pulse front both in the case of a discharge gap breakdown and in the absence of a clearly manifested breakdown, as well as for a 10-ns delay of breakdown at the leading front of a discharge current pulse. 相似文献
5.
E. Kh. Baksht V. F. Tarasenko M. I. Lomaev D. V. Rybka A. N. Tkachev S. I. Yakovlenko 《Laser Physics》2007,17(9):1124-1128
The generation of the runaway-electron beam in nitrogen and helium is studied at an oscillator voltage of about 25 kV. Various regimes of the electron beam generation with a pulse duration ranging from 200 ps to several nanoseconds are realized depending on the pressure in the gas diode. An ultrashort avalanche electron beam (UAEB) with a low (10–20%) variation in the voltage across the gap is obtained at a relatively high pressure in the gas diode. The UAEB generation can be delayed relative to the leading edge of the voltage pulse by tens of nanoseconds at low oscillator voltages. 相似文献
6.
The generation of an acoustic signal by means of voltage pulses (f = 15 kHz) applied to the electrodes of a barrier-discharge excilamp based on a Xe/Cl2 = (50?C500)/1 mixture kept at a pressure of 5?C500 Torr is studied. It is shown that, from the time variation of the acoustic signal intensity, one can judge the time instant the excilamp starts operating in a steady mode. Optimal (in power and efficiency) operating conditions of the excilamp are found (Xe/Cl2 = 240/1, p = 98 Torr, ?? ?? 9.5%). It is experimentally demonstrated that the discharge energy at a low pressure is spent largely on heating the gas. This is indicative of the volume heat release and volume glow discharge (as the pressure grows, the efficiency of this source of energy consumption drops and more and more energy is spent on acoustic vibration excitation). Under higher pressures, the Fourier spectrum of the acoustic signal becomes richer, the intensity of the spectrum rises, and the dispersion of the signal grows. At very high pressures, the intensity of the acoustic signal drops to a level corresponding to the natural vibrations of the excilamp envelope without the discharge (when the discharge is quenched, the Fourier spectrum of the signal becomes depleted and contains only harmonics corresponding to the carrier frequency of voltage pulses from the power source). 相似文献
7.
S. B. Alekseev V. M. Orlovskii V. F. Tarasenko A. N. Tkachev S. I. Yakovlenko 《Technical Physics》2005,50(12):1623-1627
Electron beam formation in krypton, neon, helium, and nitrogen at elevated pressures are experimentally investigated. It is
shown that, when the krypton, neon, and helium pressures are varied, respectively, from 70 to 760 Torr, from 150 to 760 Torr,
and from 300 to 4560 Torr, runaway electrons are beamed at the instant the plasma in the discharge gap approaches the anode
and the nonlocal criterion for electron runaway is fulfilled. The fast-electron simulation of discharge gap preionization
is performed. The simulation data demonstrate that preionization in the discharge gap is provided if the voltage pulse rise
time is shorter than a nanosecond under atmospheric pressure. 相似文献
8.
A. S. Nasibov G. L. Danielyan V. G. Bagramov K. V. Berezhnoi P. V. Shapkin 《Bulletin of the Lebedev Physics Institute》2011,38(4):101-104
The experimental results on the study of radiation of Cd x Zn1?x S semiconductor targets (STs) of the gas diode (GD) for the pressure variation from 10?1 Torr to the atmospheric pressure are presented. Pulses 0.5–1 ns long with an amplitude to 200 kV were applied to the GD cathode. Laser radiation (509 nm) was generated in the ST under a beam of accelerated runaway electrons to a pressure of 2.5 Torr. At atmospheric pressure, generation in the ST was observed in discharge channels when the streamer moved from one ST surface to another. In this case, as the electric fields strength increased, radiation sequentially arose at three spectral lines, 509, 480, and 469 nm. Possible causes of the observed phenomena are considered. 相似文献
9.
R. P. Babertsyan É. S. Badalyan G. A. Egiazaryan É. I. Ter-Gevorkyan 《Technical Physics》1998,43(9):1035-1038
A steady-state Penning ion source is studied experimentally. Depending on the geometric parameter l
a
(the anode length to diameter ratio) and pressure, maxima are observed in the discharge current and in the ion beam current
extracted from an aperture at the center of the cathode. It is shown that at pressures of the order of 10−4 Torr, two maxima appear in these currents: one, for short discharge gaps with l
a
=1–1.5, corresponds to a diverging ion beam, and the other, for longer anodes with l
a
=4–5, to a collimated ion beam. At pressures of the order of 10−5 Torr, only one maximum appears in these currents, for short anodes l
a
=2–3 with a diverging ion beam. A physical explanation is proposed for these findings.
Zh. Tekh. Fiz. 68, 29–32 (September 1998) 相似文献
10.
Scattered ionizing radiation emissions from a low-energy plasma focus (0.1 kJ Mather-type) device operating with different
gases were studied. The plasma focus device was powered by a capacitor bank of 1 μF at 18 kV maximum charging voltage. The
radiation emissions were investigated using time-integrated thermoluminescence TLD-500. These detectors were calibrated against
standard X-ray machine as well as standard γ sources (60Co and 137Ca). Calibration of detectors showed linear relation over all the region of measurements. It was found that radiation levels
would be minimum for different gases, when the gas pressure was between 0.5 and 0.8 Torr. Only helium deviated from this phenomenon
as it gave maximum radiation level at 0.8 Torr pressure. It was also found that, for all the gases used, the radiation levels
were maximum when the applied voltage was 15 keV. 相似文献
11.
N. M. Afanasyev V. S. Vasilkovskiy V. B. Kaplan I. I. Kasikov A. M. Martsinovskiy V. S. Mironov N. S. Rasor I. I. Stolyarov L. K. Hansen V. I. Yarygin 《Technical Physics》2008,53(9):1152-1161
The results of investigation of the ignition voltage for a low-voltage cesium arc and direct voltage drops in the discharge
in cesium triodes with fine-mesh (∼0.2 mm) and coarse-mesh (∼2 mm) control grids are presented. It is shown that in a cesium
vapor pressure range of 0.05–0.1 Torr and for discharge currents of 5–10 A/cm2, direct voltage drops can be reduced to 0.7–0.5 V even for a fine-mesh grid. For a coarse-mesh grid whose holdoff voltage
is sufficient for rectifying low voltages (∼15–20 V), direct voltage drops are almost the same as for a diode even for currents
of 1 A/cm2 and lower. The critical factor of holdoff voltage loss is the grid emission level (∼1 mA/cm2). 相似文献
12.
研制了一台KrF大能量准分子激光器,激光器采用紧凑型Chang电极与紫外火花预电离的结合, 实现了激活区大面积的均匀辉光放电,利用LC反转倍压以及一级磁脉冲压缩技术在放电电容上实现了峰值电压40 kV、脉冲上升时间约为100 ns的高压快脉冲激励。研究了工作气体含量对激光器能量输出的影响,在总气压3.3105 Pa,F2/He, Kr, Ne体积分数比值为1.97∶3.18∶94.85,充电电压27 kV时,得到了738 mJ的单脉冲能量输出,激光近场光斑30 mm14 mm,在充电电压23 kV时,全电效率最高,达到2.0%。 相似文献
13.
R. A. Akhmedzhanov A. L. Vikharev A. M. Gorbachev O. A. Ivanov A. L. Kolysko 《Technical Physics》1997,42(3):260-268
Results are presented from an investigation of the dynamics of ozone formation in a freely localized discharge generated by
a periodic train of 3-cm nanostructured microwave pulses in oxygen and air at a pressure p=3–30 Torr. Conditions for the efficient generation of ozone in air with the minimum production of nitrogen oxides are demonstrated
experimentally. It is shown that when the microwave pulse repetition frequency is high, heating of the gas and the buildup
of nitrogen oxides in the discharge in air reduce the ozone formation efficiency while under prolonged exposure the ozone
formed initially is destroyed. The energy cost of forming ozone in oxygen and air is determined as a function of the microwave
pulse length and repetition frequency and the gas pressure. The lowest energy cost of forming a single ozone molecule in these
experiments is 16 eV per molecule for a discharge in air and 4 eV per molecule in oxygen. It was observed that circulating
the gas through the discharge zone enhances th ozone formation efficiency. It is shown that there are optimal conditions for
ozone formation as a function of the reduced electric field in the plasma.
Zh. Tekh. Fiz. 67, 9–18 (March 1997) 相似文献
14.
The sheath is formed near the cathode immediately after applying the voltage across the electrodes. This formation is mainly due to the depopulation of this region by electrons. Using the one-dimensional model of the sheath region and the kinetic model coupled to the dielectric barrier discharge discharge electric circuit, we studied the formation of the cathode sheath and its evolution during the first pulse in Ne–Xe mixture for 10% and 20% of xenon at a total gas pressure of 400 Torr and for an applied voltage of 3 kV. The results illustrate the discharge behaviors as well as the evolution of the electric field and the charged particles in the cathode region. The effect of the xenon concentration is also studied and discussed. 相似文献
15.
E. Kh. Baksht A. G. Burachenko M. V. Erofeev M. I. Lomaev D. V. Rybka D. A. Sorokin V. F. Tarasenko 《Laser Physics》2008,18(6):732-737
A discharge in the presence of a nonuniform electric field and the generation of an ultrashort avalanche electron beam (UAEB) are studied in the insulating gas SF6 at the pressures 0.01–2.50 atm. High-voltage nanosecond pulses (about 150 and 250 kV) and the voltage pulses with an amplitude of 25 kV and a duration of tens of nanoseconds are applied across the gap. An electron beam is obtained behind the AlBe foil with a thickness of 45 μm at a sulfur hexafluoride pressure in a gas-filled diode of up to 2 atm. It is demonstrated that, at relatively high pressures (greater than 1 atm) and in the presence of high-voltage nanosecond pulses across the gap, the UAEB pulse FWHM increases. The spectra of the diffuse and contracted discharges in sulfur hexafluoride are measured. 相似文献
16.
Yu. I. Anisimov A. Ch. Mashek K. E. Metel’skii E. L. Ryabchikov 《Optics and Spectroscopy》2009,107(3):368-370
We demonstrate the possibility of creating a suspension of active-media particles in a discharge tube by using an electrodynamic
dispersing system. An electric discharge in an electrodynamically dispersed system of 30-μm Cu particles was studied. The
velocity of Cu (30 μm), Al (30 μm), and W (6-μm flakes) particles was measured at atmospheric pressure using a laser Doppler
velocimeter. The velocities were found to be in the 0.1−5-m/s range. The electric field strength required to levitate Cu,
Al, and W particles was studied as a function of buffer gas (air) pressure in the range from 2 × 10−2 Torr to 1 atm. It is shown that powders can be suspended with the help of electrodynamic dispersing system at air pressure
below 0.1 Torr or above 100 Torr. 相似文献
17.
V. F. Tarasenko S. I. Yakovlenko S. A. Shunailov I. D. Kostyrya A. N. Tkachev 《Laser Physics》2006,16(3):526-533
Subnanosecond electron beams formed in diodes filled in with a gas at atmospheric pressure and X-rays emitted from nanosecond-discharge plasmas are studied. Both phenomena hold promise for lasing technology. A three-group separation of fast electrons in a gas-filled diode is proposed. It is found that the duration of the beam current in a diode filled with air at atmospheric pressure does not exceed 0.1 ns. It is also shown that the amplitude of the beam current attains maximum with a certain delay after the application of voltage to the discharge gap. A current of ~400 A is detected behind the foil of a diode filled with air at atmospheric pressure. At a subnanosecond duration of the voltage pulse and the diffuse discharge, X-ray radiation is observed from the brightly glowing area of corona discharge. The mean steady-state velocities and energies of fast electrons in nitrogen are calculated. Head-on collisions are shown to control the constancy of the mean velocity of fast electrons for the field strengths E/p < 170 kV/(cm atm). At E/p > 170 kV/(cm atm), the escape of fast electrons takes place. It is particularly the head-on collisions that are decided to be responsible for the emission of X-rays from the bulk. 相似文献
18.
W. G. Wang Y. Xu C. Dong N. Z. Zhang K. Y. Hou H. Y. Li 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,50(3):257-264
Determinations of radical density are essential to investigate the
physical-chemical processes in plasmas and setup the related theoretical
models. This paper presents the experimental measurement of atomic hydrogen
near grounded electrode in dielectric barrier discharge medium-pressure
hydrogen plasma via threshold ionisation-molecular beam mass spectrometry.
After investigating the possible influences from parent molecules in excited
states, background component and space-charge, evolution of atomic hydrogen
density as functions of discharge parameters are investigated utilising the
signal of H2 molecule beam as the reference. At fixed gas pressure of
6.0 torr and a discharge voltage of 24 kV, atomic hydrogen density increases
monotonously from 1.1×1014 to 2.0×1015 cm-3
as the discharge frequency increases from 9 to 26 kHz. Similarly the rising
discharge voltage also lead to enhancement of atomic hydrogen density. 相似文献
19.
A. I. Klimov S. D. Korovin V. V. Rostov E. M. Tot’meninov 《Radiophysics and Quantum Electronics》2006,49(10):747-753
We consider the preconditions for efficient operation of the relativistic Čerenkov microwave generator in the absence of an
external guiding magnetic field. The analytical expression for the length of propagation of a solid cylindrical electron beam
along the drift tube is obtained in the framework of the paraxial approximation. The influence of preliminary modulation of
the electron beam on the starting current of the generator and its linear efficiency is analyzed. We calculated the geometry
of a relativistic Čerenkov microwave generator with an efficiency of about 30%, in which the solid cylindrical electron beam
propagates over a short resonance decelerating system (with the length L ≈ 3λ, where λ is the radiation wavelength) in the
absence of an external magnetic field. In experiments, the efficiency of power conversion from the high-current electron beam
into the electromagnetic radiation of the E01 mode reached 8%, approximately (relative to the total current of the vacuum diode), for a power of 1.2 ± 0.3 GW and a generation
frequency of 4.06 GHz.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 10, pp. 829–836, October 2006. 相似文献
20.
The results of experiments with a three-ring large-area diode that were conducted on an MIG pulse generator are reported.
The MIG generator makes it possible to produce in a matched load electrical pulses up to 2 TW in power with an FWHM of 50–60
ns (1.2–1.4 TW and 80–90 ns in our experiments). In the operating mode of the generator, the current amplitude through the
load is 2 MA (the current of a relativistic electron beam) at a diode voltage of ≈ 500 kV. As a load, a large-area vacuum
diode with three ring-shaped cathodes is used. It is shown that about 20% of the energy stored in the capacitor bank can be
converted to the energy of a relativistic electron beam by matching the output resistance of the MIG generator to the load
resistance. When the beam slows down on a condensed foil target, the parameters of the resulting source are the following:
the mean energy of X-ray quanta is ≈ 70 keV; irradiated area, 500 cm2; pulse FWHM, 65 ns; energy flux in the spectrum, 2 J/cm2; and percentage of X-ray radiation (10–100 keV) in the flux, ≈ 50%. 相似文献