Mechanically tuned relativistic backward wave oscillator

A high-power relativistic microwave oscillator with low magnetic field is created based on a backward wave oscillator (BWO) with resonance reflector. For fixed parameters of the slow-wave structure (SWS) and the electron beam, the oscillation frequency of this BWO can be mechanically tuned within a 12% band by moving the resonance reflector relative to the SWS. A maximum output pulse radiation power of 4±1 GW at a working frequency of 3.6 GHz is achieved with a magnetic field of 4.6 kOe.     

A periodic pulsed relativistic backward wave oscillator mechanically tunable in an expanded frequency band

We have studied a periodic pulse train regime (1 s, 50 Hz) of a relativistic backward wave oscillator with a resonant reflector, which can be mechanically tuned from pulse to pulse within a frequency band of 9% on a level of ?3 dB of the maximum in the entire microwave peak power range in a magnetic field of 0.36 T. The maximum peak power in a pulse train amounted to 2.5 GW at a frequency of 3.6 GHz, an efficiency of 20%, and a microwave pulse duration of 20 ns.     

Structure and bandgap determination of InN grown by RP-MOCVD

InN thin films are grown on sapphire substrates by remote plasma-assisted metal organic chemical vapor deposition while varying the indium pulse length and substrate temperature. The effects of the indium pulse length and temperature on the structural, morphological, electronic, and optical properties of the thin films are studied. The structural parameters are determined by X-ray diffraction and X-ray photoelectron spectroscopy and the effects of incorporating oxygen atoms in the structure is described. The N K-edge X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) measurements are used to determine the band gap and it is found to be 1.80?±?0.25 eV for all samples. A complementary measurement namely, X-ray excited optical luminescence measurement is performed to confirm the band gap value obtained from XAS and XES measurements. O K-edge XAS measurements are performed to determine the presence of oxygen impurities in the samples. Meanwhile, we carry out the density functional theory calculations for Wurtzite InN, hypothetical Wurtzite-type InO_0.5N_0.5, and InO_0.0625N_0.9375 structures. We find that the measured N-edge spectra agree well with our Wurtzite InN calculations and the measured O K-edge spectra agree better with hypothetical Wurtzite-type InO_0.0625N_0.9375 than Wurtzite-type InO_0.5N_0.5.

     

Heat Treatment of Cast Carburizing High-Speed Steel Alloyed with Ti, Nb, and V

Special features of the structure and phase composition of cast carburizing high-speed steel of the ferrite-carbide class and the laws of their variation in the process of the carburizing hold and subsequent heat treatment are described. The temperature of heating for quenching was varied within 1180 – 1220°C, and the tempering temperature was varied within 560 – 640°C using the hardness and heat resistance as criteria. The results of mechanical tests of heat treated steels are analyzed.     

A possible method of reducing the magnetic field in a relativistic backward-wave tube

A new configuration is proposed and implemented for a relativistic backward-wave tube using the symmetric TM₀₁ mode which can appreciably enhance, by a factor of 2–3, the generation efficiency of high-power 3 cm radiation pulses using low magnetic fields. Pis’ma Zh. Tekh. Fiz. 24, 43–47 (May 26, 1998)     

Thermodynamic nature of exponential empirical time dependences of strength characteristics and the failure of materials. Report 1. Creep and long-term strength

It is shown that the correlation between two parameters describing the power law of creep or the long-term-strength curve, which can be demonstrated on the basis of numerous experimental data, is governed by the thermodynamics of the processes of steady-state creep or creep-induced failure. Analytical expressions describing this correlation are obtained, and values of the parameters entering into this relationship are explained on the assumption of the logarithmic character of the dependence of the activation energy of the process on deforming stress. An independent method of evaluating the cohesive energy of the material from results of creep tests is proposed. A simple formula is presented for the a priori estimation of the slope of the long-term strength curve from the material's melting point.The paper is written as an outgrowth of a study performed by the authors, which was published in the journal Problemy Prochnosti, No. 6, 3–9 (194).Translated from Problemy Prochnosti, No. 2, pp. 5–24, February, 1996.     

Relativistic Cherenkov microwave oscillator without a guiding magnetic field

A relativistic Cherenkov microwave oscillator without a guiding magnetic field has been designed, constructed, and tested in which a continuous cylindrical electron beam propagates in a short (L ≈ 3λ, λ being the radiation wavelength) resonant slow-wave structure. The electron beam is energy-modulated at the input of the interaction space, which provides conditions for the energy exchange at a wave phase velocity exceeding the particle velocity. The effective beam-wave coupling is provided by a nearly homogeneous profile of the longitudinal electric field component of the synchronous wave in the interaction space cross section. The efficiency of power conversion from high-current electron beam to electromagnetic radiation at E₀₁ mode is about 8% at a maximum output pulse radiation power of 1.2 ± 0.3 GW and a working frequency of 4.05 GHz.