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The parameters of X-ray radiation and runaway electron beams (RAEBs) generated at long-pulse discharges in atmospheric-pressure air were investigated. In the experiments, high-voltage pulses with the rise times of 500 and 50 ns were applied to an interelectrode gap. The gap geometry provided non-uniform distribution of the electric field strength. It was founded that at the voltage pulse rise time of 500 ns and the maximum breakdown voltage Um for 1 cm-length gap, a duration [full width at half maximum (FWHM)] of a RAEB current pulse shrinks to 0.1 ns. A decrease in the breakdown voltage under conditions of a diffuse discharge leads to an increase in the FWHM duration of the electron beam current pulse up to several nanoseconds. It was shown that when the rise time of the voltage pulse is of 500 ns and the diffuse discharge occurs in the gap, the FWHM duration of the X-ray radiation pulse can reach ≈100 ns. It was established that at a pulse-periodic diffuse discharge fed by high-voltage pulses with the rise time of 50 ns, an energy of X-ray quanta and their number increase with increasing breakdown voltage. Wherein the parameter Um/pd is saved.
Results of experimental studies of the amplitude–temporal characteristics of a runaway electron (RE) beam, as well as breakdown voltage and discharge current with a picosecond time resolution are presented. The maximum pressure, at which a RE beam is detectable, decreases with increasing the voltage rise time. The waveforms of the discharge and RE beam currents are synchronized with those of the voltage pulses. It is shown that the amplitude–temporal characteristics of the RE beam depend on the designs of the gas-filled diode and cathode, as well as the gap length. The mechanism for the generation of REs in atmospheric-pressure gases is analyzed on the basis of the obtained experimental data.
In this paper, the spectra of electron beams produced in vacuum and gas diodes were analyzed to study the capabilities and limitations of their reconstruction from beam attenuation in foils of different thickness. The electron energy distributions were calculated using the Tikhonov regularization for Fredholm integral equations on minimum a priori assumptions. The spectra reconstructed in the study were those of electron beams, including a supershort avalanche electron beam, produced in experiments on a DUET plasma-cathode electron accelerator and SLEP-150M accelerator.
This paper reports on the properties of a supershort avalanche electron beam generated in the air or other gases under atmospheric pressure and gives the analysis of a generation mechanism of supershort avalanche electron beam, as well as methods of such electron beams registration. It is reported that in the air under the pressure of 1 atm, a supershort (<100 ps) avalanche electron beam is formed in the solid angle more than 2π steradian. The electron beam has been obtained behind a 45 µm thick Al-Be foil in SF6 and Xe under the pressure of 2 atm, and in He, under the pressure of about 15 atm. It is shown that in SF6 under the high pressure (>1 atm) duration (full width at half maximum) of supershort avalanche electron beam pulse is about 150 ps.
The properties of an electron beam (e-beam) formed in air under
atmospheric pressure are reported. The nanosecond generators RADAN-303
(two devices) and RADAN-220, producing nanosecond voltage pulses with
amplitude of up to 400 kV and subnanosecond rise time were used in the
experiments. It was shown for the first time that the duration of e-beam
current of gas diode behind the foil does not exceed 0.1 ns. The maximum
amplitude of current of a supershort avalanche electron beam (SAEB) behind
the foil was ∼400 A. The data on the influence of various parameters
on e-beam current amplitude measured behind the foil were obtained. An
electron beam with energy less than 60 keV and powerful X-ray radiation
were formed in discharge gap simultaneously with SAEB.
This article reports on experimental studies of subnanosecond
electron beams formed in air under atmospheric pressure. An electron
beam with an amplitude of ∼170 A with a duration at FWHM of
∼0.3 ns has been obtained. Based on beam temporal characteristics
and discharge spatial characteristics, the critical fields were
supposed to be reached at plasma approach to anode. Simultaneously, the
sharp high-energy pulse of e-beam current is generated. Of critical
importance is the cathode type and occurrence on the cathode of plasma
protrusions. It is shown that to get maximum amplitude of the electron
beam in the gas diode, the discharge in the gas diode should be
The spectral and amplitude-temporal parameters of HF (DF) lasers
pumped by nonchain chemical reactions initiated by radially
convergent or planar e-beams and self-sustained discharge were
studied. Intrinsic efficiency of the HF lasers up to ∼10%
was obtained for both excitation methods. It was shown that
the high efficiency of an e-beam-initiated HF laser may be attained
as a result of the simultaneous formation of atomic and molecular
fluorine and of the participation of F2 in population
inversion. A laser pulse has a complex profile caused by the
successive generation of P-lines and the overlap during the
radiation pulse of both the rotational lines of the same vibration
band and of individual vibration bands. Experimental conditions
providing high intrinsic efficiency of a discharge nonchain
HF (DF) laser are determined. Intrinsic efficiency of HF and
DF lasers up to ηin ∼ 10% and 7%,
respectively, is obtained using excitation by inductive and LC
generators in the SF6-H2 (D2)
mixtures. High discharge uniformity obtained with the use of
special shaped electrodes along with uniform UV preionization
is a key parameter for improving the intrinsic efficiency of
discharge HF (DF) lasers. It was found that in this excitation
condition, output spectra of the HF laser significantly widen and
cascade laser action on some rotational lines of the vibrational
transitions of HF molecules ν(3–2) → ν(2–1)
→ ν(1–0) is observed. This can explain the high intrinsic
efficiency obtained. Specific output of the discharge HF laser
over 8 J/L (140 J/L×atm) and total laser efficiency
ηt ∼ 4.5% were achieved. For the
discharge DF laser, specific output and total efficiency were as
high as 6.5 J/L and 3.2%, respectively.
The interaction of Xe (λ ∼ 1.73 μm) and XeCl (0.308
μm) laser radiation with surfaces of metal and TiN-ceramic
coatings on glass and steel substrates has been studied.
Correlation between parameters of surface erosion versus
laser-specific energy was investigated. Monitoring of laser-induced
erosion on smooth polished surfaces was performed using optical
microscopy. The correlation has been revealed between
characteristic zones of thin coatings damaged by irradiation
and energy distribution over the laser beam cross section allowing
evaluation of defects and adhesion of coatings. The interaction
of pulsed periodical CO2 (λ ∼ 10.6 μm),
and Xe (λ ∼ 1.73 μm) laser radiation with surfaces
of teflon (polytetrafluoroethylene—PTFE) has been studied.
Monitoring of erosion track on surfaces was performed through
optical microscopy. It has been shown that at pulsed periodical
CO2-radiation interaction with teflon the sputtering
of polymer with formation of submicron-size particles occurs.
Dependencies of particle sizes, form, and sputtering velocity
on laser pulse duration and target temperature have been obtained.
A high-current accelerator for pumping of the 200-L excimer
laser is developed, providing electron energy of 550 keV, a
diode current of 320 kA, and an e-beam current of 250 kA. The
high-voltage part of the accelerator consists of two linear
transformers with a stored energy of 98 kJ. To reduce the influence
of the self-magnetic field on e-beam formation, the vacuum diode
is divided into six separate magnetically isolated diodes.
The results on study of light sources based on spontaneous
radiation of molecules KrCl* (λ ∼ 222 nm) and XeCl*
(λ ∼ 308 nm) excited by a glow discharge are presented.
It is demonstrated that additions of light inert gases (He and
Ne) lead to increase in emission of radiation power and efficiency
in mixtures Kr(Xe)-Cl2. A high-power cylindrical
multi-section excilamp was built and energy, time, and spectrum
characteristics have been studied. Average output power obtained
in the UV spectral range were 1,9 kW at λ ∼ 222 nm and
1,1 kW at λ ∼ 308 nm with efficiencies with respect
to the excitation power of up to 14%.
Calculations of optimal parameters for the e-beam excited
Xe spontaneous radiation source (excilamp) at λ ∼
172 nm have been done. There have been defined optimal
values of gas density and specific excitation power. Gas
temperature dependence of radiation conversion efficiency
related to the injected media energy have been also computed.
It has been shown that there is an optimum in excitation
pulse duration at frequency operation mode.
The main goals of this review article are to show, on the basis of the results accumulated in this field, achievements in simulating the processes in nuclear pumped laser (NPL) active media by experiments on e-beam pumping, and to give a number of characteristic experimental examples, when this simulation has improved understanding of the inversion population processes in NPL active media (Cd+, Xe-lasers) or generated interest in experiments with fission fragments excitation (Ne-laser). In the case of the population of laser operation levels in non-equilibrium recombinating plasma, one can say with sufficient accuracy that the inversion population mechanism is identical for both excitation types.
Results of an experimental study of a coaxial exciplex lamp pumped by glow discharge are presented. An average power of radiation in the wavelength region below 250 nm and as high as about 130 W has been achieved. Efficiency of the excilamp operation based on input power of 14% was demonstrated. The possibility of applications of this excilamp is discussed.
The design scheme of a radially convergent 30-, 70-, or 100-μs e-beam-pumped laser with 9 or 18 1 excited volume is described. Amplitude, temporal, and spectral characteristics of the laser output, as well as laser thresholds in (Ar–Xe, He–Ar–Xe, He–Ne–Ar, and He– Ne–Ar–H2) gas mixtures have been investigated. The distribution of the specific deposited energy over the laser chamber cross section has been calculated by the Monte Carlo method. The small signal gain and unsaturable loss values of the active medium were measured for a Penning plasma Ne laser at λ = 0.585 μm.
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