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The article observes the main provisions of the clinical recommendations for prevention, anesthesia and intensive care for postpartum hemorrhage. The main risk factors, possible complications, principles of clinical and laboratory diagnosis in this pathology are consistently presented. Particular attention is paid to issues of infusion, transfusion therapy and correction of coagulopathic disorders. The problems of estimating the amount of blood loss, diagnosing disorders of the hemostatic system, regulation of hemodynamics in hemorrhagic shock are discussed. The use of recombinant coagulation factors in coagulopathy on the background of massive blood loss has been substantiated.

The first stage of the experimental study of a frequency adjustable FEM-oscillator with a broadband microwave system based on the effect of microwave beams multiplication is presented. Operability of the key element of this system (wide-band reflector) was tested in the “hot” experiment. The 45 GHz FEM-oscillator with a microwave system of the new type was driven by a 500 keV, 120 A, 20 ns electron beam and generated 7 MW of radiation with a 12% efficiency. A new double-resonance operating regime of the FEM with combined - undulator and homogeneous guide - magnetic field, when both the undulator and the cyclotron resonance conditions are fulfilled simultaneously, was realized.

Operability of the wide-band reflector based on the effect of microwave beams multiplication was tested in the "hot" experiment. A microwave system of the new type including such a reflector was used in a free electron maser (FEM)-oscillator with a guide magnetic field. The high-current accelerator "Sinus-6" forming a 500 keV/120 A electron beam was used as the FEM driver. The double-resonance regime, when both the undulator and the cyclotron resonance conditions were fulfilled simultaneously, provided maximum output power 7 MW and electron efficiency 12% at the designed frequency 45 GHz.

A new scheme of self-exciting single-cavity gyromultiplier is tested in a preliminary mm-range experiment. Such a scheme is prospective for realization in THz range.

The paper presents recent test results on low relativistic (20-80 kV) gyro-TWT and gyro-BWO based on a microwave system in the form of a waveguide with helical surface. In particular, in experiments the Ka-band gyro-TWT showed the following output parameters: pulse power up to 180 kW, gain 25-30 dB, instant frequency band 10%, efficiency at second harmonic operation 27%. The gyro-BWO was designed for CW operation with output power of 5-7 kW at frequencies around 24 GHz. Smooth frequency tuning in the band of 10% was demonstrated.

The paper presents recent test results on low relativistic (20-80 kV) gyro-TWT and gyro-BWO based on a microwave system in the form of a waveguide with helical surface. In particular, in experiments the gyro-TWT showed the following output parameters: pulse power up to 180 kW, gain 25-30 dB, instant frequency band 10%, efficiency at second harmonic operation 27%.

Summary form only given. The gyrotron traveling wave tube (gyro-TWT) is a well-known amplifier variety of the gyro-devices, which may have a wide instantaneous frequency bandwidth because of the operation with an electromagnetic wave possessing large group velocity. For a microwave system in the form of a smooth cylindrical waveguide a large wave group velocity inevitably leads to a large axial wavenumber, which makes this device significantly more sensitive to particle velocity spread in comparison with a gyrotron. The most favorable wave dispersion for a gyro-TWT is that when the wave group velocity is sufficiently large and constant in the region of close-to-zero axial wavenumber. A similar dispersion can be realized in an oversized circular waveguide with special helical ripples of its inner surface A theoretical analysis demonstrates important advantages of the "helical" gyro-TWTs over the analogous "smooth" ones in sensitivity to electron velocity spread, frequency bandwidth and stability to parasitic self-oscillations. The proof-of-principle experiments exploiting moderately relativistic (200-300 keV) short-pulse (20-100 ns) field-emission electron beams have proved the main theoretical predictions. Based on the first successful experiments and the developed theory, a project was started aimed at the creation of a more applicable device. The main goal of this project is the realization of a Ka-band gyro-TWT with a low-relativistic electron beam produced by a gun with a thermionic cathode.

Simultaneous generation at the second and fourth cyclotron harmonics has been obtained from a single-cavity self-excited gyromultiplier. Output power of the short-wavelength radiation amounts to 100 W at a frequency of 75 GHz. The proposed scheme seems to be promising for the terahertz frequency range.