Ion energy cost in a combined inductive-capacitive rf discharge

Experimental measurements were made of the ion energy cost η as a function of the parameters of a combined rf inductive-capacitive discharge at low pressures (p<10⁻² Torr). It was established that η does not depend on the power supplied, it has a minimum as a function of pressure, and also decreases when an rf potential is applied to the electrodes. The results can be used to find the optimum parameters in terms of energy efficiency of ion formation and may be useful for refining the theoretical models of a combined rf inductive-capacitive discharge. Pis’ma Zh. Tekh. Fiz. 24, 33–39 (November 26, 1998)     

The “zero” current and self-sustaining electron bunches in M-type devices

When the processes occurring in the entire interaction space of a magnetron device are included simultaneously in a numerical simulation it is possible to observe the onset and behavior of stable solitary electron bunches. It is shown that these self-sustaining electron bunches may be responsible for the existence of an anode current in the absence of rf interaction. Pis’ma Zh. Tekh. Fiz. 24, 57–62 (June 26, 1998)     

Excitation of a potentially self-oscillating state in an oscillator with delay and inertia exposed to the simultaneous action of regular and chaotic signals

An analysis is made of the possibility of inducing a potentially self-oscillating state in a bistable self-oscillating system exposed simultaneously to regular and chaotic signals, as applied to the covert transfer of information in a binary computational system. A system of nonlinear differential difference equations is derived, which describe the behavior of an oscillator with delay and inertia under the action of complex oscillations in a given time interval. It is shown numerically that even when a potentially self-oscillating state is not excited by an external regular signal, stochastic oscillations, as well as providing a masking effect, may function as an additional stimulus to transfer the system to the basin of attraction of a potentially selfoscillating attractor. Pis’ma Zh. Tekh. Fiz. 23, 66–71 (July 26, 1997)     

Metal-insulator cathode in an rf electron gun

The possibility of using metal-insulator cathodes in rf guns of 10 cm linear resonant electron accelerators has been studied experimentally for the first time. Results of calculations and the development of a prototype cathode are described. Results of an experimental investigation of the operating regimes of an rf gun are presented. The gun delivered a beam having a particle energy greater than 300 keV, a pulse length of 40–50 ns, and a pulsed current of 3.5–4.5 A. Pis’ma Zh. Tekh. Fiz. 24, 36–39 (October 12, 1998)     

Growth of cubic GaN by molecular-beam epitaxy on porous GaAs substrates

It is shown that GaN layers can be grown on (100)-and (111)-oriented porous single-crystal GaAs substrates by molecular-beam epitaxy with plasma activation of the nitrogen by an rf electron cyclotron resonance discharge. The resulting undoped epitaxial layers possessed ntype conductivity with a carrier concentration ∼10¹⁸. Data obtained by scanning electron microscopy and cathodoluminescence indicate that at thicknesses ∼2000 Å, continuous layers of the cubic GaN modification are obtained regardless of the substrate orientation. Pis’ma Zh. Tekh. Fiz. 25, 3–9 (January 12, 1999)     

Localization of an rf capacitive discharge in a long strip line

The self-consistent problem of a an intermediate-pressure rf capacitive discharge in a long strip line is analyzed with allowance for heating of the gas. Steady-state distributions of the discharge parameters along the line are derived. It is shown that the discharge burns in certain regions, whose lengths and locations depend on the amplitude of the applied voltage. Pis’ma Zh. Tekh. Fiz. 23, 64–70 (January 26, 1997)     

Formation of macroparticle structures in an rf induction discharge plasma

It was demonstrated experimentally that macroparticles may undergo levitation and form ordered structures in an rf induction discharge plasma. The experiments were carried out using 1.87 μm melamine formaldehyde particles in neon at a pressure of 25–500 Pa. The generator frequency was 100 MHz. Pis’ma Zh. Tekh. Fiz. 24, 62–68 (October 12, 1998)     

Growth of GaN by molecular-beam epitaxy with activation of the nitrogen by a capacitive rf magnetron discharge

It is shown that GaN films can be grown by molecular-beam epitaxy with plasma activation of the nitrogen by a magnetron rf discharge in a specially constructed coaxial source with capacitive coupling. A growth rate of ∼0.1 μm/h is obtained on GaAs and sapphire substrates, and ways are found for optimizing the design of the plasma source in order to increase the growth rate. The electrophysical and luminescence properties of undoped epitaxial films are investigated at temperatures ranging all the way to room temperature. Pis’ma Zh. Tekh. Fiz. 24, 30–35 (June 26, 1998)     

Low-pressure inductive rf discharge in a rare gas-halogen mixture for economical mercury-free luminescence light sources

It is demonstrated that an inductive rf discharge in an Xe+Cl₂ mixture may be used as the active medium of an efficient, mercury-free luminescence light source. Pis’ma Zh. Tekh. Fiz. 24, 63–67 (March 26, 1998)     

Hot deformation behavior of Ti-15-3 titanium alloy: a study using processing maps,activation energy map,and Zener–Hollomon parameter map

The hot deformation behavior of Ti-15-3 titanium alloy was investigated by hot compression tests conducted in the temperature range 850–1150 °C and strain rate range 0.001–10 s⁻¹. Using the flow stress data corrected for deformation heating, the activation energy map, processing maps and Zener–Hollomon parameter map were developed to determine the optimum hot-working parameters and to investigate the effects of strain rate and temperature on microstructural evolution of this material. The results show that the safe region for hot deformation occurs in the strain rate range 0.001–0.1 s⁻¹ over the entire temperature range investigated. In this region, the activation energy is ~240 ± 5 kJ/mol and the ln Z values vary in range of 13.9–21 s⁻¹. Stable flow is associated with dynamic recovery and dynamic recrystallization. Also, flow instabilities are observed in the form of localized slip bands and flow localization at strain rates higher than 0.1 s⁻¹ over a wide temperature range. The corresponding ln Z values are larger than 21 s⁻¹. The hot deformation characteristic of Ti-15-3 alloy predicted from the processing maps, activation energy map, and Zener–Hollomon parameter map agrees well with the results of microstructural observations.     

High-efficiency narrow-band free-electron maser using a Bragg cavity with a phase discontinuity in the ripples

A new, highly selective Bragg cavity system having phase discontinuity in the ripples inside the interaction space was used to develop a free-electron maser based on the LIU-3000 accelerator (free-electron maser oscillator). This system operated at 30.7 GHz with a power of around 50MW and an efficiency of 35%, which is the highest yet recorded for this class of system. Pis’ma Zh. Tekh. Fiz. 25, 19–28 (June 12, 1999)     

Determination of electron transport coefficients in argon from ignition curves of rf and combined low-pressure discharges

Ignition curves of rf and combined (rf+static electric field) low-pressure discharges are used to determine the electron drift velocity V _dr in the range E/p≈70−2000 V/(cm·Torr) and the ratio of the longitudinal diffusion coefficient to the electron mobility D _L /μ _e in the range E/p≈ 1−2000 V/(cm·Torr). Pis’ma Zh. Tekh. Fiz. 24, 49–55 (April 26, 1998)     

Mass spectroscopic measuring of SiCl<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 0–2) radicals in SiCl<Subscript>4</Subscript> RF glow discharge plasma

The relative densities of SiCl _n (n = 0–2) in SiCl₄ radio frequency (rf) glow discharge plasma are measured by mass spectrometry. The effects of discharge parameters, i.e., rf power, discharge pressure, substrate temperature, and SiCl₄ flow rate on the relative densities of SiCl _n (n = 0–2) are investigated in detail. An optimum configuration of discharge parameters (low rf power, high discharge pressure, low substrate temperature, and low flow rate), which enhanced the formation of SiCl _n (n = 0–2) radicals, is searched by a great deal of measurements and discussions. In the optimum configuration of discharge parameters, we measure the spatial distribution of SiCl _n (n = 0–2) radicals in the most optimized plasma parameters. The experimental results reveal that Si and SiCl may be the dominant precursors in forming the thin film.     

Sealed efficient excilamps excited by a capacitive discharge

The development of sealed XeCl (λ∼308 nm), KrCl (λ∼222 nm), and XeI (λ∼253 nm) excilamps excited by a capacitive rf discharge is reported. It is shown that highly efficient emission of exciplex molecules is achieved under capacitive discharge excitation and the emitter has a simple design. An average emission power of 3W was obtained with a ∼12% efficiency and the lifetime of the sealed excilamps was longer than 1000 h. Pis’ma Zh. Tekh. Fiz. 25, 27–32 (November 12, 1999)     

Experiments on interferometric enhanced scattering in a plasma with a nonuniform magnetic field

Results are presented from the first experiments on interferometric enhanced scattering (IES) in a plasma in a nonuniform magnetic field. Measurements of the lower hybrid fluctuations of the plasma density by the IES and rf probe methods in an experimental geometry that models a tokamak configuration are found to be in satisfactory agreement. Pis’ma Zh. Tekh. Fiz. 24, 43–51 (October 26, 1998)     

Electronic energy spectrum of the sheath of an asymmetric low-pressure capacitive rf discharge

The high-energy part of the electron energy spectrum of the plasma of an asymmetric capacitive low-pressure rf discharge in air associated with electron beams near the electrodes is studied experimentally. It is found that the energy distributions obtained under different conditions contain a beam peak, both quasimonoenergetic and substantially broadened in energy. It is established on the basis of quantitative estimates that the substantial damping of the electron beam is due to the excitation of collisionally dissipative and collisionless beam-plasma instabilities. Pis’ma Zh. Tekh. Fiz. 25, 32–39 (October 12, 1999)     

Resistive state and charge imbalance waves in superconducting indium bridges with large cross section

We have investigated the Josephson behavior in indium microbridges with 2 µm thickness, 5–8 µm width, and 9–21 µm length. The resistive behavior of the bridges can be described by a dynamic model consisting of an ideal Josephson oscillator emitting charge imbalance waves into the adjacent superconductor. From the analogy between the charge imbalance wave equation and the telegraph equation a useful equivalent circuit is obtained, as pointed out recently by Kadin et al. The Josephson behavior in the different regimes of amplitude and frequency of the rf current superimposed upon the dc current is discussed.     

Possibility of using a large orbit regime for operation at bounce-frequency harmonics in a free-electron maser with a guiding magnetic field

It is suggested that a free-electron maser based on the LIU-3000 accelerator (Joint Institute for Nuclear Research, Dubna) can be made to emit in the short-wavelength part of the microwave range by using radiation at harmonics of the bounce frequency of an electron beam propagating along a helical trajectory with a large gyration radius on the transverse inhomogeneity scale of the rf field and selectively exciting a cylindrical waveguide mode whose azimuthal index is equal to the number of the harmonic. Pis’ma Zh. Tekh. Fiz. 25, 30–36 (January 12, 1999)     

Modified method of plasma-enhanced chemical vapor deposition of nanocrystalline silicon

A modified plasma-enhanced chemical vapor deposition technology is developed for nanocrystalline Si which combines the standard rf glow discharge method and the hollowcathode discharge method in a single process cycle. The volume fraction of nanocrystallites varied monotonically along the layer, whereas their size remained constant. The electrical and optical characteristics of these films were investigated. Pis’ma Zh. Tekh. Fiz. 24, 26–30 (October 12, 1998)     

Relationship between the spectra of time series of a flow system and its recurrent map

The relationship between the dynamical systems with continuous time (flows) and discrete time (maps) has been studied. It is shown how some important characteristics of a flow system can be modified during the Poincaré sectioning procedure, and which information about the flow system behavior can be obtained from the resulting map. The results of theoretical analysis are illustrated by numerical simulations for the model Rössler system and “Torus” oscillator.