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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
volumetric.
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.
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