V. I. Ivannikov

Microwave field effects on the time dependence of recombination fluorescence from non-polar solutions

Abstract A novel experimental setup to study the effect of microwave field on the kinetics of recombination fluorescence from nonpolar solutions irradiated with nanosecond X-ray pulses is described. Experiments on the observation of the microwave field effects in dodecane and hexane solutions are presented. The most favorable conditions for observation of the microwave induced quantum oscillations are found. The effect of spin locking was observed for the first time in the time-resolved microwave field effects. An efficient method to calculate the spin evolution of a radical pair in a microwave field taking into account relaxation is suggested. Analytical expressions for the microwave field effect in the limiting cases of large and small hyperfine splittings are given.

Bandpass characteristics of coupled resonators

A system of series-coupled transmission cavity resonators formed from sections of regular waveguides separated by coupling windows is considered. Bandpass characteristics of this system are obtained by representing the fields in the cavities in the form of a sum of the waves scattered by the windows. A method for measuring the intercavity coupling coefficient for two coupled resonators is presented and a good agreement between the calculated and measured characteristics is demonstrated.

The system of RF beam control for electron gun

The system of RF control of three-electrode electron gun current is described. It consists of a source of microwave signal, coaxial line, coaxial RF switch and RF antenna lead. The system allows one to get the electron beam in the form of bunches with the frequency of the accelerating section to achieve the capture of particles in the acceleration mode close to 100%. The results of calculation and analysis of the elements of the system are presented. Characteristics of the devices are obtained experimentally. The results of using RF control in three-electrode electron gun at electron linear accelerator are described.

Characteristics of a chemical reactor that is a loaded microwave resonator

Relationships for calculation of the following parameters of reactors with microwave heating of chemical reagents are presented: the coefficient of absorbed microwave energy distribution in the reactor (in the cavity between the resonator walls and reagents) and the efficiency of transformation of microwave energy into heat of the reagents. The range of variation of microwave properties of the reactor during variation of reagent properties is estimated, and the coupling parameters of the resonator with the external line that provide for a high efficiency are determined.

The effect of accelerating cavity’s transients on the particle energy spread

An accelerating resonator loaded by current is analyzed based on an equation for normalized amplitude of the oscillations obtained by the method of counterpropagating waves. An expression for the accelerating voltage is derived with allowance for transients observed upon enabling the generator and beam. The effect of transients on the particle energy spread is taken into account. A possibility of stabilizing the beam energy at an arbitrary phase of the generator and without detuning the accelerating resonator in the process of transition to the steady state is demonstrated.

Spectrometer for Optical Detection of the Electron Spin Resonance with an Increased Level of Microwave Power

A spectrometer for optical detection of the electron spin resonance (ESR) spectra of short-lived radical-ion pairs produced by ionizing radiation is described. The setup is based on a standard ESR spectrometer equipped with an adapter for optical detection of spectra and a microwave amplifier. In a solution of n-terphenyl in alkanes, the spin-locking effect has been observed. At a microwave power of 10 W, the microwave magnetic induction is 0.5 mT.

Heating efficiency of chemical reagents in the microwave cavity

Relationships for technical calculation of the parameters of reactors with microwave heating of chemical reagents are presented. The range of variation of microwave properties of the reactor during variation of reagent properties is estimated, and the coupling parameters of the resonator with the external line providing high efficiency are determined. The experimental data of the absorption degree of microwave energy by different chemical objects in the high-Q resonator are obtained.

A superhigh-frequency attachment to the pulse X-ray fluorimeter

A unit for creating in the area of the analyzed sample a pulsed microwave field with a 2.45-GHz frequency, a 10-ns fall time, and a rotating component of the magnetic induction with a maximum amplitude of 0.8 mT is described. The fast pulse decay is obtained by creating a pulsation mode in the system consisting of two coupled resonators. The duration of the flat top of the microwave pulse is regulated from 0 to 400 ns, and the maximum pulse repetition rate is 16 kHz. The unit is used in the nanosecond X-ray fluorimeter to control the spin state of the spin-correlated ion-radical pairs in nonpolar solutions.

A Device for the Formation of Short Microwave Pulses in a High Quality Factor Cavity

Microwave pulses at a frequency of 2.45 GHz with a duration of 30–55 ns (at the base level) were obtained using the effect of fast energy transfer in a pair of coupled cavities. The pulse repetition rate reached 40 kHz, and the maximum magnetic-induction amplitude was 0.32 mT at a 20-W generator power.

Radio-frequency power compressor

An rf power compressor is proposed which contains two standing-wave cavities mounted to the side wall of the waveguide to form amplified rf pulses.