It is my pleasure to present the Special Issue of Laser and Particle Beams devoted to the 25th anniversary of the Institute of High Current Electronics (IHCE) of the Russian Academy of Sciences Siberian Division.

This paper reviews the physical phenomena that accompany the emission of electrons and ions from plasma. The development of plasma emission electronics as an independent research field is closely associated with the name of its founder, Professor Kreindel Yu. E. The well-known advantages of plasma electron emitters (plasma cathodes) are the higher emission current density, the pulsed emission capability, and the wider range of residual gas pressures. A peculiar property of the plasma cathode is the possibility of extracting practically all electrons from plasma. The parameters of an ion and electron beam extracted from plasma carry information about the physical processes occurring in the plasma. This makes it possible to invoke emission methods to study the fundamental phenomena that take place in plasma of vacuum arc and low-pressures gas discharges.

This paper is devoted to the engineering embodiment of the modern methods for producing charged ion and electron beams by extracting them from the plasma of a discharge. Electron beams use to execute electron-beam welding, annealing, and surface heating of materials and to realize plasmochemical reactions stimulated by fast electrons. Ion beams allow realization of technologies of ion implantation or ion-assisted deposition of coatings thereby opening new prospects for the creation of compounds and alloys by the method that makes it possible to obtain desired parameters and functional properties of the surface. A detailed description is given to the performance and design of devices producing beams of this type: the ion and electron sources being developed at the laboratory of plasma sources of the Institute of High-Current Electronics of the Russian Academy of Sciences and the laboratory of plasma electronics of Tomsk State University of Control Systems and Radioelectronics.

This article reviews experiments on the production of low-energy, high-current electron beams (LEHCEB) and their use for surface modification of materials. It is shown that electron guns with a plasma anode and an explosive emission cathode are most promising for the production of this type of beams. The problems related to the initiation of explosive emission and the production and transportation of LEHCEBs in plasma-filled diodes are considered. It has been shown that if the rise time of the accelerating voltage is comparable to or shorter than the time it takes for an ion to fly through the space charge layer, the electric field strength at the cathode and the electron current density in the layer are increased. Experimentally, it has been established that the current of the beam transported in the plasma channel is 1–2 orders of magnitude greater than the critical Pierce current and several times greater than the chaotic current of the anode plasma electrons. Methods for improving the uniformity of the energy density distribution over the beam cross section are described. The nonstationary temperature and stress fields formed in metal targets have been calculated. The features of the structure-phase transformations in the surface layers of materials irradiated with LEHCEBs have been considered. It has been demonstrated that in the surface layers quenched from the liquid state, nonequilibrium structure-phase states are formed.

This article describes S-band sources of high-power microwave (HPM) pulses: a resonant backward wave oscillator (BWO) producing ∼5-GW, 100-J pulses, based on the SINUS-7 electron accelerator, and a double-section vircator with a peak power of ∼1 GW and a pulse width of 20–50 ns, powered from either the SINUS-7 accelerator or the MARINA inductive-store pulse driver with a fuse opening switch.

This article presents results of theoretical and experimental studies on the production of ultrashort (a few RF cycles duration) microwave pulses of gigawatt peak powers based on superradiance from high-current electron beams. With the Cherenkov backward-wave–electron-beam interaction in a low-dispersion slow-wave structure, microwave pulses with a peak power greater than the peak power of the driving electron beam have been produced for the first time. In an experiment using the SINUS-150 compact high-current electron accelerator, with a 2.6-kA injected beam current and a 330-kV electron energy, microwave pulses of 1.2 GW peak power and ∼0.5 ns duration (FWHM) were generated in the X-band. Production of superradiance pulses in a repetitive regime (3500 Hz) in the Ka-band has been demonstrated using a compact hybrid SOS-modulator. The effect of spatial accumulation of microwave energy in extended slow-wave structures with substantially nonuniform coupling has been demonstrated. In an experiment using the SINUS-200 compact accelerator, X-band pulses of ∼3 GW peak power and 0.6–0.7 ns width (FWHM) were produced with a power conversion efficiency of 150–180% and an energy efficiency of ∼15%.

This article describes the principles of operation and the parameters of the SINUS setups designed at the Institute of High-Current Electronics, Siberian Division, Russian Academy of Science, over the period from 1990 to 2002. A characteristic feature of accelerators of the SINUS type is the use of coaxial forming lines (in particular, with a spiral central conductor) which are charged by a built-in Tesla transformer to produce the accelerating high-voltage pulses. This ensures a reasonable compactness and long lifetime of the setups.

The article presents a source producing high-power ultrawideband electromagnetic pulses. The source includes a generator of monopolar pulses, a bipolar pulse former, and a combined ultrawideband transmitting antenna. Monopolar 150-kV, 4.5-ns pulses are transformed into bipolar 120-kV, 1-ns pulses, which are emitted by the antenna. The pulse repetition rate of the setup is up to 100 Hz. The peak power of the source is 170 MW as measured with a TEM-type receiving antenna having 0.2–2 GHz passband. The pattern width of the transmitting antenna at a half-level of peak power is 90° and 105° for the H- and E-planes, respectively. The electric field strength measured 4 m from the transmitting antenna in the direction of the main radiation maximum is 34 kV/m.

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 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.

We present two-dimensional simulation results of the formation and evolution of a diffuse plasma channel in the XeCl pumping discharge. Channel formation was initiated by metallic convexity at the cathode surface with a characteristic dimension of ∼0.1 cm. Two pumping regimes were considered. Initial voltage in the second regime was increased 1.6 times and impedance was decreased 2 times in contrast with the first regime. Evolutions and spatial distributions are presented for electron density, electric field, and frequencies of the main process. In the first regime, the diffuse plasma channel forms. The main processes causing development of the plasma channel are inhomogeneous distribution of the electric field, increase of the stepwise ionization frequency at ne ∼ 1015 cm−3, and depletion of HCl. Increasing of the initial voltage and decreasing of the impedance in the second regime results in a quick rise of the discharge current and electron density in the discharge gap, and uniform discharge takes place during the current pulse.

High-current electron beams with a current density of up to 100 A/cm2 generated by a plasma-cathode gas-filled diode at low accelerating voltages are studied. Two types of gas discharges are used to produce plasma in the cathode. With glow and arc discharges, beam currents of up to 150 A and 400 A, respectively, have been obtained at an accelerating voltage of 16 kV and at a pressure of 1–3·10−2 Pa in the acceleration gap. The ions resulting from ionization of gas molecules by electrons of the beam neutralize the beam charge. The charge-neutralized electron beam almost without losses is transported over a distance of 30 cm in a drift channel which is in the axial magnetic field induced by Helmholtz coils. The results of calculations for the motion of electrons of the charge-neutralized beam with and without axial external field are presented and compared with those of experiments.

This article presents two types of a hollow-cathode plasma source based on an arc discharge where the electrons emitted either by a hot filament or by a surface-discharge-based trigger system initiate a gas arc discharge. The sources produce gas plasmas of densities 1010–1012 cm−3 in large volumes of up to 0.5 m3 at a discharge current of 100–200 A and at a pressure of 10−1–10−2 Pa. Consideration is given to some peculiarities of the operation of the plasma sources with various working gases (Ar, N2, O2). The erosion rate of the cold hollow cathode in the designed plasma sources is shown to be 10 times lower than that found in an ordinary one. The sources are employed for plasma-assisted surface modification of solids.

A double shell z-pinch with an axial magnetic field is considered as a K-shell plasma radiation source. One-dimensional radiation-hydrodynamics calculations performed suggest that this scheme holds promise for the production of the K-shell radiation of krypton (hν ≈ 12–17 keV). As a first step in verifying the advantages of this scheme, experiments have been performed to optimize a neon double-shell gas puff with an axial magnetic yield for the K-shell yield and power. The experiments show that the application of an axial magnetic field makes it possible to increase the K-shell radiation power and reduce the shot-to-shot spread in the K-shell yield. Comparisons between the experiments and modeling are made and show good agreement.

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 condition for the transition of the electron beam produced in a coaxial rod-pinch diode to the mode of magnetic insulation has been established from the law of conservation of particle and field momentum fluxes. The magnetic field of the external current has been shown to contribute twice as much to magnetic insulation of the beam as the magnetic field of the electron beam self-current. Based on the relations derived, a model has been constructed for magnetic insulation of the electron flow in high-current rod-pinch diodes, which are used for radiography of high speed phenomena. The obtained theoretical results agree well with the results of numerical calculations and with experimental data gained at the Naval Research Laboratory (USA).

Cylindrical magnetrons with rotating cathodes have found wide application in the thin-film coating deposition technologies owing to a higher degree of the target utilization and used power level as compared with planar magnetrons. The aim of this work was to increase the efficiency of cylindrical magnetrons. It is known that the region of uniform coatings deposition with extended magnetrons is essentially lower than the sputtered cathode length. The actual achievable cathode utilization degree is limited, with the regions at cathode ends having a higher wear rate than the central part. To eliminate these shortcomings, experiments were carried out on the creation of a magnetic system to allow an increase of the coating deposition uniformity and target utilization. Resulting from the investigations that were carried out, a magnetic system design with an increased magnetic field at its ends (by 5–15%) and modified turn-around parts has been developed. This magnetic system design allows extending the coating deposition region with the uniformity of ±1% by 12.5 cm and completely eliminating accelerated erosion of the end cathode parts. The obtained results are promising for use in technologies of deposition of thin-film coatings with a high degree of uniformity (no worse than ±1%) onto large-area substrates.

The general possibility of the extended (∼30 cm) closed-drift ion source application for deposition of wear-resistant amorphous hydrogenated carbon (a-C:H) films on large-area dielectric substrates, in particular, on carbon-fiber plastic, is shown. Parameters of the “ion” and the “plasma” regimes of the ion source operation in argon and methane are defined. It is shown that the ion current nonuniformity is in the range of ±5–15% depending on the operation mode. Optimum conditions for the substrate precleaning in argon and hard, well-adhered a-C:H films deposition from methane are determined. The films are characterized by high hardness (∼11 GPa) and low surface roughness (∼0.13 nm) that leads to a several times lower friction coefficient (0.05) and wear rate (0.001 μm3m−1N−1) compared to glass and carbon-fiber plastic substrates.

Good adhesion of thin films to the substrate is obviously necessary for any practical applications. Ion beam and plasma treatment are used to establish enhanced adhesion of thin films at dielectric substrates. It was supposed that both these processes could lead either to removal of contaminant layers as a result of surface heating and desorption or to production of stable chemical bonding within the metal–substrate interface. The article shows that the second process is the dominant factor.

Primary storages based on a linear transformer scheme were developed long ago. In this scheme, the secondary turn only has to be insulated from the high output voltage. Seven years ago at the High Current Electronics Institute (HCEI) a primary storage based on a linear transformer scheme and called the Linear Transformer Driver (LTD) stage was designed. In LTD stages, the primary turn, the storage capacitors with the switches, the core, and the outer conductor of the secondary turn are integrated into the stage cavity representing one separate building block of the primary storage. The body of the LTD cavity keeps ground potential during the shot allowing us to assemble them in series or in parallel depending on load requirements. Such flexibility of the storage structure and high output power of the LTD stages allows us to replace for some applications the traditional water line technology with LTD-based primary storages that are connected directly to the load (Direct Drive Scheme—DDS). In this article, we present the design of several LTD stages developed at HCEI and give examples of high-power energy storages produced by using the LTD technology.