Various repetitive pulsed power generators have been developed for different applications. Semiconductor switches have greatly extended the scales of pulsed power parameters, especially in repetition rate and lifetime. They have also enabled new areas of pulsed power applications, such as accelerators, flue-gas treatment, and gas lasers.

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Abstract Operation mode of an oversized backward wave oscillator is studied experimentally, using an oversized slow-wave structure. The dispersion characteristics of the slow-wave structure are determined by the average radius, corrugation amplitude and pitch length of the periodic waveguide. The corrugation amplitude and the corrugation period mainly determine the upper cutoff frequency of the lowest mode. The lower cutoff frequency is determined by the average radius. In this work, a Q-band periodic slow-wave structure is fabricated from aluminum. The diameter of the slow-wave structure is about 4 times free space wavelength. The beam voltage is weakly relativistic, around 50 kV, and the beam current is in the range of 100 A. The output powers of several 10 kW are obtained in the Q-band, i.e., the estimated frequency is in the range of 34-41 GH. The output modes are examined by measuring the radiation patterns. Nonaxisymmetric as well as axisymmetric modes are observed. It is demonstrated for the first time that the nonaxisymmetric and axisymmetric operations of the oversized BWO can be controlled by changing the corrugation number of slow-wave structure.

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We propose an electron bunch acceleration and trapping mechanism by an intense short laser pulse in vacuum. By using a short laser pulse obtained by the linear combination of a TEM₁₀ mode and a TEM₀₁ mode with the same amplitude and the relative phase shift of π/2, the electrons are accelerated in the longitudinal direction by a longitudinal ponderomotive force, and the electrons divergence in the transverse direction can be suppressed by a transverse ponderomotive force. In order to analyze the electron motion, the relativistic equation of motion including a relativistic radiation damping effect is solved. In our calculations, the electron is accelerated to 179 [MeV] with an acceleration gradient of 5.12 [GeV/m] at the laser intensity of 1.23×10¹⁸ [W/cm²]. The rms emittances of the electron bunch accelerated are (1.06, 1.21, 0.348) [mm mrad] in the x, y and z directions, and the spatial size of this electron bunch accelerated in the radial and longitudinal directions are 856 [μm] and 11.7 [μm], respectively.

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Characteristics of ion beams produced in the Mather type plasma focus (P.F) were studied experimentally to apply the beam to materials processing. The plasma focus was pre-filled with H₂ of 250 Pa, or mixture of H₂ (270 Pa) and Ne (30 Pa). At 218 mm downstream from the top of the anode on the electrode axis, ion beam of current density ≈ 4 kA/cm², pulse width ≈ 100 ns (FWHM) was observed when filling gas of H₂ was used. The ion species and energy spectra were evaluated by a Thomson parabola spectrometer. Protons of energy in the range of 0.1-1.4 MeV are observed when PF was filled with H₂. From the X-ray measurement pinch plasma column of 3-4 mm in diameter and 40 mm in length is observed and line emission of He-like and H-like K shell X-ray emissions were observed when PF was filled with mixture gas. Measurement of pinhole image and an incident angle resolved proton energy spectrum ion production is found to be axial symmetry and the ion energy decreases with increasing incident angle. To evaluate the irradiation effect amorphous silicon thin films of thickness 500 nm was irradiated by the ion beam. By the X-ray diffraction measurement of the films before and after the irradiation we found that the film was poly-crystallized by the irradiation.

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A pulsed discharge in water was applied to inactivate Cryptosporidium parvum (C. parvum) in filter backwash water from a water purification plant. Effects of water quality and discharge conditions on the degree of inactivation were investigated by batch experiments. A high inactivation ratio (> 99%) was obtained under conditions of low turbidity and high total energy. In 10L backwash water of turbidity 40, 98% of oocysts were inactivated by applying a total energy of 17520 J for 10L (1752 J/L). Experimental results suggest that UV emission is mainly effective for inactivation.

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Cherenkov and slow cyclotron instabilities driven by an axially injected electron beam in periodically corrugated cylindrical waveguide are studied by using a new version of self-consistent linear theory considering three dimensional beam perturbations. For the bounded microwave systems, the self-consistent boundary conditions require all field components and the normal modes in the beam are hybrid of transverse magnetic (TM) and transverse electric (TE) modes, even in the axisymmetric case. The slow cyclotron instability as well as Cherenkov instability can be driven by the axially streaming electron beam without any initial perpendicular velocity. In the low magnetic field region, the charge caused by the radial displacement of the beam plays an important role in the beam interaction with the electromagnetic mode. The radial displacement become large by decreasing the magnetic field and the slow cyclotron instability becomes strong and compete with the Cherenkov instability. For the axisymmetric case, the Cherenkov instability is dominant and suppresses the slow cyclotron instability, On the other hand, the slow cyclotron instability becomes dominant and suppresses the Cherenkov instability, for the nonaxisymmetric mode with the left-hand circular polarization

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The work covers the research results of plasmochemical synthesis of silicon dioxide nanosize powder out of the gas-phase mixture of silicon tetrachloride, hydrogen and oxygen. The process was initiated by the high-current pulsed electron beam. Chain plasmochemical synthesis was carried out at volumetric reaction excitation. Distribution of the particles under size criteria was shown. Particle growth under further influence of pulsed electron beam was discovered. It is shown that the process has an oscillation character similar to cold flame regime at hydrocarbon oxidation

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The aim of this work was to investigate adhesion increasing of titanium nitride coating deposited at hard alloy tool’s surface pretreated by intense pulsed ion beam of different energy density. Two alloys were treated by high-power pulsed ion beam of 1÷3.75 J/cm² energy density. Analyzing the data obtained from tunnel microscopy, X-ray spectrum and measurements of surface relief geometry characteristics, such as roughness and profile length, we came to the following conclusion. First, the value of energy density of ion beam plays the key role in the formation of the relief and phase structure of the surface. Second, these two characteristics are almost independent of the initial characteristics of the irradiated alloys.
Also, the article touches the results of scratch-test of the titanium nitride coating. The results demonstrate changes in wearing and destruction mode of the coating deposited at the tool treated by ion beam.

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To increase energy-to-electron-beam transfer effectiveness accumulated in the double forming line of high-current electron accelerator, the matching transformer with outside magnetization placed between forming line and diode module was used. Transformer core saturation to line charging phase allows to decrease greatly pre-pulse amplitude and its influence on anode foil durability without switch sharpening application. Accelerator provides electron beam generation with pulse energy up to 200 J at electron kinetic energy 500 keV and pulse length 60 ns. Nanosecond voltage generator and explosive emission diode effectiveness were investigated.

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Chromium oxynitride (Cr-N-O) thin films have been successfully prepared by using pulsed laser deposition (PLD). The oxygen content in the thin films (x) was controlled by changing experimental conditions. The Cr-N-O thin films with x = 30at. %, which had NaCl (B1) structure at room temperature (RT), maintained B1 phase even at T= 800°C. Moreover, Vickers hardness of such thin films was clarified to be approximately 3000 in the T ranging from RT to 800°C.

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Spectroscopic methods recently developed for the measurements of electricfields, magnetic fields, and plasma properties in various pulsed-power systemsare described. The methods utilize spectroscopy of visible-UV and X-rayemission-lines and of laser radiation. They allow for non-perturbingmeasurements with relatively high spectral, temporal, and spatial resolutions. Spatial resolution along the line of sight is obtained by locally doping theplasma with various species whose emission is then utilized. A few methodsdeveloped for doping solid and gaseous materials are described. Results for anion diode, nanosecond and microsecond Plasma Switches, and a pinch system are presented.

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We have investigated numerically and experimentallycharacteristics of diode perveance and output microwave power incoaxial virtual cathode oscillator (vircator). In this experiment, the diode perveance characteristics could be described using thediode voltages and currents. The sheath plasma expansion speed isto be about 7cm/μs under A-K gap distance 4 mm. We have alsoinvestigated an influence of anode-cathode (A-K) gap distance onoutput characteristics of high power microwave from coaxialvircator. In this experiment, the maximum microwave power isobserved to be 244 MW, whose efficiency is about 2.75 %, at theA-K gap distance of 4 mm. The microwave frequencies are alsomeasured to be 5.1 ≤ f ≥ 5.9 GHz from combination ofcoupled line band pass filter with 1 GHz band gap and dispersivedelay line. With microwave reflector, the maximum output microwavepower is observed to be about 400 MW, whose efficiency is about7.1 %, at the A-K gap distance 8 mm and microwave reflectorinner-hole diameter of 7.6 cm. The microwave frequencies are alsomeasured to be 4.8 ≤ f ≥ 5.2 GHz.

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A three-frame Mach-Zehnder interferometer (TFMZI) was used for taking 3 pictures (5 ns exposure and 13 ns interpicture delay) of the imploding plasma in one z-pinch shot, which provides us a series of interferograms showing the evolution of electron density profile during z-pinch implosion stage. From these interferograms, the electron density profile n_e(r , z), the velocities of plasma implosion were derived, and the plasma instabilities appearing as bubbles or fringe shearing were observed clearly. In order to study the correlation between the total energy of x-ray emission and the plasma implosion, thermopiles were also used in the experiments with TFMZI. The results of x-ray radiation diagnostics show us that a near uniform and symmetric imploding plasma shell would emit more x-ray yield than an asymmetric one, which is in good agreement with the implosion dynamics analyses.

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The third continuum is obtained by electron beam pumping argon. The range of the continuum is from 200nm to 300nm. The optimum conditions of the third continuum are studied. Firstly, the effects of the argon gas pressure on the intensity of the continuum are studied. And the optimum pressure is about 0.3MPa. Secondly, the effects of the current and voltage of the electron beam on the continuum are observed. Between 251kV and 466kV in diode, the intensity of the continuum is increase with voltage. And between 13.3kA and 20.2kA in diode, the same trend can be obtained.

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The closing process of a gas peaking switch was divided into two phases, gas breakdown and voltage collapse. The gas breakdown phase starts from an electron avalanche and ends at a streamer connecting electrodes. The criterion for an electron avalanche to transit to streamer was considered as the criterion of gas breakdown. The voltage collapse begins immediately after the gas breakdown. The spark channel theory developed by Rompe-Wiezel was used to calculate the spark resistance. The discharge in the switch with pressurized hydrogen or nitrogen under very fast charging voltage was numerically simulated. The switch delay as well as the breakdown voltage and the rise time of output voltage from the switch were determined. The results from the calculations show good agreement with the results from experiments.

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