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The effect of nanosecond repetitive pulsed microwaves (RPMs 10 GHz, 100 ns pulse duration, 8 and 13 Hz pulse repetition rate, 140 W/cm2 peak power flux density (pPFD)) on the regeneration of burn wounds in rats was studied. It is established that after 4-fold local irradiation of wounds with intensity of 140 W/cm2 at pulse repetition rates of 8 and 13 Hz stimulates the healing of burn wounds. A comparison of the obtained results allows us to state that nanosecond low-intensity RPMs of 140 W/cm2 accelerate wound healing processes. At the same time, the impact with a pulse repetition rate of 8 Hz turned out to be more effective in comparison with a pulse repetition frequency of 13 Hz. Histological analysis of rat skin showed an increase in the rate of wound healing due to the accelerated formation of granulation tissue, a decrease in the thickness of eschar and scarless healing.

In this paper, we give a review of some most powerful pulsed systems developed at the Institute of High Current Electronics (HCEI), Siberian Branch, Russian Academy of Sciences, and describe latest achievements of the teams dealing with these installations. Besides the presented high-power systems, HCEI performs numerous investigations using much less powerful generators. For instance, last year much attention was paying to the research and development of the intense low-energy (

The effect of nanosecond repetitive pulsed microwaves on the possibility of triggering a stress response of laboratory mice was investigated. The exposure was carried out every day once per a day during the 5 days' period (4000 pulses per session) with repetition rates of 8, 13, 16 and 22 pulses per second. The source of radiation was a laboratory pulse generator based on a magnetron MI-505 with a carrier frequency of 10 GHz, a pulse duration at half the power level of 100 ns, an output peak power of 180 kW, an electric field strength of 1.5 103 V/cm, a peak power density of 1.5 × 103 kW/cm2). It was found that repeated exposure alters the level of corticosterone in the blood serum. The effect depends on the frequency of repetition of microwave pulses. Possible mechanisms of the effect of radiation on the level of corticosterone are considered.

The quasi-stationary mode of operation of a high-efficiency 38-GHz nanosecond relativistic microwave backward-wave oscillator at a pulse repetition rate of 10 Hz has been demonstrated. A hybrid modulator based on an SM-3N SOS driver and on an energy compression unit containing a pulse-forming line and a spark gap was used to produce 5-ns electron-beam-accelerating pulses of the trapezoidal shape. Optimization of the energy exchange between the weakly magnetized electron flow and the oncoming harmonics of the TM01 wave inside the periodic slow-wave structure has made it possible to achieve a peak power of ~170 MW for 4-ns microwave pulses at an electron efficiency no less than 30-35%.

Laser interferometry was recently used to diagnose plasma formation and evolution in the slow wave structure (SWS) of a relativistic backward wave oscillator (BWO) during the course of microwave generation. The results indicated that plasma from the cutoff neck inlet contributed to the termination of the high power microwave pulse. In an effort to mitigate this pulse shortening effect, the authors have replaced the cutoff neck with a Bragg reflector. As part of these studies, they have observed the cross-excitation instability because of the particularly shallow-ripple SWS used. They present results from recent experiments performed with the long pulse relativistic BWO, including the implementation of a hybrid-hard tube BWO at the University of New Mexico (UNM).

For three years we performed a set of experiments that demonstrated the generation of ultra high-power Ka-band pulses by using superradiative relativistic BWOs high efficiency generation was obtained at a low B-field (2 T) below the cyclotron resonance. With the use of DC solenoid, SR pulses were generated in a batch mode at PRF of 1000-3500 Hz. The "beam-to-microwaves" power conversion exceeding a factor of 1.5 was achieved in the Ka-band. (4 pages)

The effect of X-band HPM pulses from a SINUS-500 relativistic HPM source on Drosophila melanogaster embryos, larvae, and pupae was studied. The test objects were irradiated with 10-ns pulses during 5-min batches at a pulse rate of 3-29 p.p.s. The peak microwave power was 500 MW, the electric field in the irradiation zone was /spl sim/1.5/spl times/10/sup 4/ V/cm and the X-ray dose was 1-3 /spl mu/Rad per pulse. To understand the mechanisms of the effects and to estimate the comparative contribution of microwave and X-ray components of the SINUS-500 radiation, the objects were also exposed to (a) X-ray-free microwave pulses from a magnetron (wavelength 3 cm, pulse width 730 ns, pulse power up to 40 kW, electric field at the object /spl sim/1.5/spl times/10/sup 3/ V/cm), (b) pure X-ray pulses produced in the periodically-pulsed regime by the SINUS-500 facility where the microwave component was cut by a metal screen, and (c) continuous X-rays with nearly the same dose and exposition time (2-30 mRad during 5 min). The irradiation caused notable disturbance in the individual development of Drosophilas in the form of increased PID, teratism of imagoes, delay of imago fly etc. The strength of the effects was dependent upon the stage of development of the organism at the moment of irradiation, and the pulse repetition rate. Repeated extra exposures did not increase the effect. The pulses from the SINUS-500 facility produced a stronger effect than magnetron pulses. The strength of X-ray pulse action depended on the pulse rate while the effect from continuous X-rays was negligibly small. The paper discusses possible mechanisms of action of nanosecond HPM pulses.