IAP RAS Research Articles

Transformation of the Shape and Spectrum of an Ultrawideband Electromagnetic Pulse in a “Gigantic” Coaxial Line Filled with Magnetized Plasma

A propagation of ultrawideband electromagnetic pulses (UWB EMPs) through magnetized plasma has been experimentally studied using a “gigantic” coaxial line, which has been developed at IAP RAS for laboratory modeling of ionospheric effects. This coaxial line is 1.4 m in diameter and 10 m in length and is installed inside the chamber of the large-scale Krot plasma device. The line can be filled with rf inductively coupled plasma, magnetized or not. It allows one to explore the propagation of UWB EMPs in plasma along a long path without refraction and divergence and obtain a physical picture of EMP transformation. Under conditions where the duration of the UWB EMP is comparable to the period of electron plasma oscillations (fp−1), the period of cyclotron rotation of electrons (fc−1), or even significantly shorter, a complex of effects of transformation of the waveform and frequency spectrum of the pulse occurs. Without ambient magnetic field, a UWB EMP is distorted due to the effects of the cutoff and frequency dispersion. In dense magnetized plasma, i.e., when fp >> fc, the UWB EMP breaks into two wave packets, the high-frequency one (f > fp) and low-frequency one (f < fc). In rare magnetized plasma (fp << fc), the cyclotron absorption produces a long train of damped oscillations at a frequency close to the cyclotron frequency fc following the UWB EMP.

Design and Testing of the Photogun Resonator and Biperiodic Accelerating Structure with Traveling Wave for the Photoinjector at the IAP RAS

Design and Testing of the Photogun Resonator and Biperiodic Accelerating Structure with Traveling Wave for the Photoinjector at the IAP RAS

A COMPOSITE MODEL OF MICROWAVE SCATTERING FROM WATER SURFACE IN EXTREME WIND SPEED CONDITION

Experiments were carried out in the wind-wave flume of Large Thermo-Stratified Wind-Wave Tank of IAP RAS aimed at studying the mechanisms of cross-polarized microwave radiation scattering from water surface under conditions of extremely high wind speeds. It is shown that the normalized radar cross-section (NRCS) can be represented as the result of an incoherent addition of contributions from breaking wave crests and from non-breaking wind waves. The effect of smoothing the water surface after passing the breaking crest made it possible to measure the NRCS of the breaking area on cross-polarization, while no dependence of the NRCS on wind speed and incidence angle was revealed. NRCS on non-breaking wind waves was calculated within the framework of the small slope approximation (SSA) using experimentally measured wind wave spectra. It is shown that the NRCS on cross-polarization increases monotonically with increasing wind speed, including hurricane conditions. In this case, the contribution of non-breaking wind waves to the NRCS saturates at wind speeds above 25 m/s. The monotonous increasing NRCS at higher wind speeds is associated with a breaking area increasing. A composite model of microwave radiation scattering from wave-covered water surface has been constructed, which has been verified on the basis of comparison with measurement data. The possibility of constructing a geophysical model function for ocean conditions based on the proposed composite model is shown, which can be used for remote sensing of sea storms and hurricanes.

Application of Chemical Metallization of Photopolymer Structures Additive Technology in the Production of Components for Electronic Devices.

In this paper, we studied the operability of various components of vacuum electronic devices manufactured using the novel chemical metallization of photopolymer 3D-printed structures technology (CMPS), which is being applied at the Institute of Applied Physics, Russian Academy of Sciences (IAP RAS), for operation from microwave to sub-terahertz ranges. The key feature of this production method is the 3D printing (SLA/DLP, MJM technologies) of products and their further metallization. The paper presents the main stages of the process of chemical copper plating of polymer bases in various electrodynamic systems with complex shapes. A significant difference in the geometry and operating conditions of the created elements forms certain approaches to their production, as described in this work. Experimental studies of the implemented microwave components were carried out up to 700 GHz in the "cold" measurements; some electrodynamic structures were examined under conditions of sub-gigawatt peak power; and complex-shaped electrodes with cooling channels were tested under a continuous high thermal load. The conducted research has demonstrated the high potential of the developed methods of additive manufacturing of microwave device components and the prospects for their successful application in the described areas.

The electron beam of the linear induction accelerator with kiloampere current as a driver for the submillimeter free electron laser

The project of a submillimeter free electron laser (FEL) based on a relativistic electron beam (REB) generated in a linear induction accelerator (LIA) was proposed at the BINP SB RAS together with the IAP RAS. According to our theoretical analysis, the electron beam generated in the LIA (energy \({{E}_{e}} = 5{\text{--}}10\) MeV, current \({{I}_{b}} = 1{\text{--}}2\) kA, normalized emittance \({{\varepsilon }_{n}}\) ~ 1100 π · mm · mrad) is a suitable driver for generating sub-GW pulses of coherent EM radiation in submm range (0.3–1 THz). The main proposals for the creation of the FEL based on the electron beam generated in the LIA are presented, the main project tasks are outlined, and the proposed methods for their solution are described. The results of electron-optical experiments on the formation of an electron beam intended for FEL applications are presented.

NONLINEAR PHENOMENA DURING THE PROPAGATION OF POWERFUL NANOSECOND ELECTROMAGNETIC PULSES IN A LARGE-SCALE STRIPE LINES WITH A GAS AT REDUCED PRESSURE

Experiments of propagation of the high-power high-voltage nanosecond and subnanosecond pulses in large-scale transmitting lines in various gases make it possible to solve a wide range of fundamental and applied problems, from simulating the propagation of electromagnetic pulses (EMP) through the atmosphere to estimating the electrical strength of elements of pulsed high-voltage gas-filled systems. At the IAP RAS, experiments with stripe lines up to 5 m in length are performed in Krot and Sprite devices. During the propagation of EMP with an electric field strength up to 100 kV/m in a low pressure gas, the effects are observed such as the formation of non-uniform and essentially non-stationary glow, nonlinear absorption and dispersion transformation of the shape of high-power pulses, due to gas ionization in the EMP field.

Electrodynamic system for powerful THz-band free-electron laser based on linear induction accelerator “LIU”: simulations and “cold” tests

The current stage of development of powerful long-pulse free-electron laser (FEL) of the terahertz band carried out in the BINP RAS in collaboration with the IAP RAS based on the linear induction accelerator “LIU” with an energy of 5–10 MeV, a kA-level current, and a pulse duration of up to 200 ns is described. To ensure a stable narrow-band generation regime, the project proposes the use of two alternative types of the electrodynamic system: advanced Bragg resonators and quasi-optical Talbot-type resonators. We discussed design parameters of the FEL based on these resonators and results of their simulations under conditions of substantial oversize. Operability of resonators of the novel types was demonstrated in the “cold” electrodynamic tests.

Effect of Sulfur Dioxide as a Component of the Volatile Organic Compounds of Fungi of the Genus <i>Lecanicillium</i> on the Phytophagous Western Flower Thrips and Peach Aphid

Earlier, using the MS7-200 quadrupole mass spectrometer developed by the IAP RAS, sulfur dioxide was detected as part of volatile organic compounds (VoCs) released into the air by entomopathogenic fungi (EPF) of the genus Lecanicillium. In this work, we evaluated the effect of this compound on such dangerous phytophages as the Western flower thrips Frankliniella occidentalis and the peach aphid Myzus persicae in low doses corresponding to the content of sulfur dioxide in the composition of VOCs over the growing mycelium of fungi. It was found that sulfur dioxide did not have a negative effect on female thrips F. occidentalis and their fertility when sulfur dioxide is injected into vials at concentrations of 9 and 17 ppm and kept for 2 hours. At a dose of 33 ppm, sulfur dioxide caused a 10% mortality of female thrips after 2 hours and 15.4% after 1 day, while a 36% decrease in female fertility was observed. Sulfur dioxide at concentrations of 17-33 ppm was nontoxic for peach aphid females after 2 hours. Aphid mortality at the level of 26% was noted after 2 days at a sulfur dioxide concentration of 33 ppm, while fertility decreased by 22%. At a dose of 23 ppm, sulfur dioxide reduced the fertility of aphids most significantly - by 30%. The data obtained indicate the influence of sulfur dioxide contained in the composition of fungal VOCs on the behavioral reactions of phytophages.

Optical Coherence Tomography Angiography of the Intestine: How to Prevent Motion Artifacts in Open and Laparoscopic Surgery?

(1) Introduction. The problem that limits the intraoperative use of OCTA for the intestinal circulation diagnostics is the low informative value of OCTA images containing too many motion artifacts. The aim of this study is to evaluate the efficiency and safety of the developed unit for the prevention of the appearance of motion artifacts in the OCTA images of the intestine in both open and laparoscopic surgery in the experiment; (2) Methods. A high-speed spectral-domain multimodal optical coherence tomograph (IAP RAS, Russia) operating at a wavelength of 1310 nm with a spectral width of 100 μm and a power of 2 mW was used. The developed unit was tested in two groups of experimental animals-on minipigs (group I, n = 10, open abdomen) and on rabbits (group II, n = 10, laparoscopy). Acute mesenteric ischemia was modeled and then 1 h later the small intestine underwent OCTA evaluation. A total of 400 OCTA images of the intact and ischemic small intestine were obtained and analyzed. The quality of the obtained OCTA images was evaluated based on the score proposed in 2020 by the group of Magnin M. (3) Results. Without stabilization, OCTA images of the intestine tissues were informative only in 32-44% of cases in open surgery and in 14-22% of cases in laparoscopic surgery. A vacuum bowel stabilizer with a pressure deficit of 22-25 mm Hg significantly reduced the number of motion artifacts. As a result, the proportion of informative OCTA images in open surgery increased up to 86.5% (Χ2 = 200.2, p = 0.001), and in laparoscopy up to 60% (Χ2 = 148.3, p = 0.001). (4) Conclusions. The used vacuum tissue stabilizer enabled a significant increase in the proportion of informative OCTA images by significantly reducing the motion artifacts.

75 GHz Relativistic Surface-Wave Oscillator of Planar Geometry

We present the results of simulations and experimental studies of a W-band surface-wave oscillator powered by a ribbon high-current relativistic electron beam produced by SINUKI accelerator (IAP RAS, Nizhny Novgorod, 1 kA / 650 keV / 17 ns). Planar geometry of the interaction space facilitates efficient mode selection over wide transverse coordinate by using open waveguide at fairly large oversize factor (the width of the waveguide is ~8 wavelengths). Stable oscillation regime is obtained at frequency of 75 GHz with a pulse duration of about 5 ns. The output power measured by the calorimetric method reaches 25 MW.

MORPHOLOGY OF BIOAEROSOL PARTICLES IN THE SURFACE LAYER OF THE ATMOSPHERE OF MOSCOW METROPOLIS

Morphological properties of biogenic particles in the near-surface aerosol composition were studied by scanning electron microscopy in Moscow. We analyze the results of complex experiment conducted in 2019–2022 at the IAP RAS to study the variability of aerosol physico-chemical properties in a large city under various weather conditions. The main types of bioaerosol particles were determined, as well as their shape and size. For the first time, brochosomes were detected in the surface aerosol in Moscow during field aerosol observations.

High-selective spatially-extended Bragg resonators implementing three-dimensional distributed feedback for powerful free electron lasers

Novel scheme of Bragg resonators implementing three-dimensional distributed feedback is proposed. The study of their electrodynamic characteristics in the framework of the coupled wave approach has been carried out and high selective properties for the three mode indices have been demonstrated under conditions of substantial oversize. The results of the theoretical analysis are corroborated by the 3D simulations. The prospects of using these resonators in the project of a super-power terahertz-band free electron laser, which is currently being developed at the BINP RAS (Novosibirsk) in collaboration with the IAP RAS (Nizhny Novgorod), are discussed. Keywords: free-electron lasers, high-power terahertz radiation, Bragg resonators, three-dimensional distributed feedback, mode selection.

Высокоселективные пространственно-развитые брэгговские резонаторы, реализующие трехмерную распределенную обратную связь, для мощных лазеров на свободных электронах

Novel scheme of Bragg resonators implementing three-dimensional distributed feedback is proposed. The study of their electrodynamic characteristics in the framework of the coupled wave approach has been carried out and high selective properties for the three mode indices have been demonstrated under conditions of substantial oversize. The results of the theoretical analysis are corroborated by the 3D simulations. The prospects of using these resonators in the project of a super-power terahertz-band free electron laser, which is currently being developed at the BINP RAS (Novosibirsk) in collaboration with the IAP RAS (Nizhny Novgorod), are discussed.

Experimental Studies of Microwave Tubes with Components of Electron–Optical and Electrodynamic Systems Implemented Using Novel 3D Additive Technology

Novel additive technology of the Chemical Metallization of Photopolymer-based Structures (CMPS) is under active elaboration currently at the IAP RAS (Nizhny Novgorod). The use of this technology has made it possible to implement components of electron–optical and electrodynamic systems for high-power microwave vacuum tubes, such as a gyrotron and a relativistic Cherenkov maser, the design and experimental studies of which are described in this paper. Within the framework of the gyrotron developments, we carried out a simulation of the distribution of the heat load on the collector of high-power technological gyrotron taking into account secondary emission. The prospect of a significant reduction in the maximum power density of the deposited electron beam was shown. The experimental study of the gyrotron collector module manufactured using CMPS technology demonstrated high potential for its further implementation. Recent results of theoretical and experimental studies of a spatially extended Ka-band Cherenkov maser are presented. In this oscillator, the 2D-periodical slow-wave structure made by the proposed technology was applied and a narrow-band generation regime was observed with a sub-GW power level. The design and simulations of a novel selective electrodynamic system for a high-harmonic gyrotron with the planned application of the CMPS technology are discussed.

Columnar and surface urban aerosol in the Moscow megacity according to measurements and simulations with the COSMO-ART model

Abstract. Urban aerosol pollution was analyzed over the Moscow megacity region using the COSMO-ART (COSMO – COnsortium for Small-scale MOdelling, ART – Aerosols and Reactive Trace gases) online coupled mesoscale model system and intensive measurement campaigns at the Moscow State University Meteorological Observatory (MSU MO, 55.707∘ N, 37.522∘ E) during the April–May period in 2018 and 2019. We analyzed mass concentrations of particulate matter with diameters smaller than 10 µm (PM10), black carbon (BC) and aerosol gas precursors (NOx, SO2, CHx) as well as columnar aerosol parameters for fine and coarse modes together with different meteorological parameters, including an index characterizing the intensity of particle dispersion (IPD). Both model and experimental datasets have shown a statistically significant linear correlation of BC with NO2 and PM10 mass concentrations, which indicates mostly common sources of emissions of these substances. There was a pronounced increase in the BC/PM10 ratio from 0.7 % to 5.9 %, with the decrease in the IPD index related to the amplification of the atmospheric stratification. We also found an inverse dependence between the BC/PM10 ratio and columnar single-scattering albedo (SSA) for the intense air mixing conditions. This dependence together with the obtained negative correlation between wind speed and BC/PM10 may serve as an indicator of changes in the absorbing properties of the atmosphere due to meteorological factors. On average, the relatively low BC / PM10 ratio (for urban regions) of 4.7 % is the cause of the observed relatively high SSA = 0.94 in Moscow. Using long-term parallel aerosol optical depth (AOD) measurements over the 2006–2020 period at the MSU MO and under upwind clean background conditions at Zvenigorod Scientific Station (ZSS) of the IAP RAS (55.7∘ N, 36.8∘ E), we estimated the urban component of AOD (AODurb) and some other parameters as the differences at these sites. The annual mean AODurb at 550 nm was about 0.021 with more than 85 % of the fine aerosol mode. The comparisons between AODurb obtained from the model and measurements during this experiment have revealed a similar level of aerosol pollution of about AODurb=0.015–0.019, which comprised 15 %–19 % of the total AOD at 550 nm. The urban component of PM10 (PM10urb) was about 16 µg m−3 according to the measurements and 6 µg m−3 according to the COSMO-ART simulations. We obtained a pronounced diurnal cycle of PM10urb and urban BC (BCurb) as well as their strong correlation with the IPDs. With the IPD index change from 3 to 1 at night, there was about a 4 times increase in PM10urb (up to 30–40 µg m−3) and a 3 times increase in BCurb (up to 3–3.5 µg m−3). At the same time, no pronounced daily cycle was found for the columnar urban aerosol component (AODurb), although there was a slight increase in model AODurb at night.

Model estimates for climatic effects of anthropogenic GHG emission scenarios in the 21st century

To estimate the climatic effects of anthropogenic CO2 and CH4 emission scenarios we performed numerical experiments using IAP RAS CM global climate model. Emissions pathways of 5 RCP (Representative Concentration Pathways) regions were used as evaluated scenarios. It is shown that the anthropogenic contribution of CO2 to global surface temperature change starts to decrease in the second half of the century only for RCP 2.6 and only for ASIA, OECD and REF emission scenarios. The rest of the CO2 emission scenarios contribute to an increase in the global surface temperature of the atmosphere throughout the 21st century. The growth of the compensatory effect of natural CO2 fluxes generally slows down by the end of the 21st century. Impact of anthropogenic methane emissions on climate stabilizes in the 21st century for all scenarios under RCP 2.6, 4.5 and 6.0. The estimates of GHG climatic cost equal up to 24 mK per PgC for CO2 and up to 0.9 mK per Tg for CH4. Methane is shown to have at least 40 times stronger impact on global surface temperature per molecule than CO2.

Variability of near-surface aerosol composition in Moscow in the spring of 2020

The paper studies variability in mass concentration and elemental composition of near-surface aerosol in Moscow in March-April 2020. During the study period, noticeable fluctuations in concentration of surface aerosol caused by atypical synoptic and meteorological conditions were revealed. Sharp increase in PM10 particle concentration (March 25-29, April 13) is associated with anticyclonic activity and advection of air containing combustion aerosols from the areas with biomass fires. In April as a whole, anomalously low values of aerosol particle concentrations were recorded in comparison with the long-term average. The prevailing dry Arctic air masses significantly decreased the atmospheric aerosol pollution. The decrease of anthropogenic load during COVID-19 non-proliferation actions affected on daily variations of the surface aerosol, smoothing out its typical daily maximal concentration values. Results of spring experiment at the IAP RAS showed good agreement with the data of the Obuchi nearest station of State Budgetary Institution "Mosecomonitoring". We analyzed geochemical spectrum of chemical elements in aerosol and its variability under different synoptic and weather conditions in Moscow. Possible sources and sinks of aerosols are discussed taking into account both abnormal weather conditions and decreased anthropogenic load during a lockdown period in the spring of 2020.

Development of Powerful Spatially Extended W-Band Cherenkov Maser of Planar Geometry With Two-Dimensional Distributed Feedback

A powerful spatially extended planar Cherenkov maser project operating in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${W}$ </tex-math></inline-formula> -band is under development in collaboration between Budker Institute of Nuclear Physics of the Russian Academy of Sciences (BINP RAS) (Novosibirsk) and Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS) (Nizhny Novgorod). The ELMI accelerator (1 MeV/5–7 kA/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3~\mu \text{s}$ </tex-math></inline-formula> ) forms a sheet electron beam with the transverse size (width) of up to 18 cm, which serves to drive the oscillator. The electrodynamic system of this Cherenkov maser is based on doubly periodical structure, which combines the properties of a slow wave system that realizes conditions for an effective Cherenkov interaction with a high-current rectilinear sheet electron beam and a high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> resonator that implements the mechanism of two-dimensional distributed feedback and provides selective excitation of the operating mode in the strongly oversized interaction space. In this article, the crucial elements and design parameters of the oscillator are discussed, and the results of simulations are presented to demonstrate the possibility of achieving a stable narrow-band generation regime for a transverse system size reaching about 50 wavelengths and a gigawatt output power level. To provide a single-directed output of radiation, a planar Bragg reflector is elaborated for installation at the cathode side of the interaction space. A mode converter formed by a slowly tapered waveguide section for transformation of the radiated wavebeam into a Gaussian-type wavebeam was designed to be installed at the oscillator output. In the electron-optical experiments, the formation of a large-width sheet electron beam with parameters acceptable to drive designed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${W}$ </tex-math></inline-formula> -band Cherenkov maser is demonstrated.

Design of the proton injector for compact neutron source DARIA

Project of the proton accelerator-driven compact neutron source DARIA (Dedicated for Academic Research and Industrial Application) is developed in order to replace small and middle flux neutron sources based on the nuclear reactors. DARIA has a uniquely high ratio of efficiency to cost due to deep optimization of each key element of the system (proton injector and accelerator, target, neutron moderator and neutron instruments. A unique ECR ion source, developed at the IAP RAS, would be used as a proton beam injector. In such device the plasma is heated by the powerful 28 GHz gyrotron radiation, providing a record level of volumetric energy input for such systems over 100 W/cm^3. The high plasma density and the optimal electron temperature provide proton beams formation with a current of up to several hundred mA and an emittance that meets the requirements of modern accelerators. The paper discusses the advantages of using such an ion source, its scheme and design performance.

Ion beam source upgrade of the neutron source at IAP RAS

The results of the ion source of the neutron generator upgrade, which makes it possible to operate in a CW mode, are presented. A magnetic trap consisting of permanent magnets (NdFeB) was developed. A 3-electrode extraction system equipped with a magnetic lens was used to extract the deuterium ion beam. Calculations are made for the formation of a deuterium ion beam with a current over 500 mA and an energy of 100 keV with practically no losses in the extraction system. Keywords: extraction system, magnetic trap, neutron generator, ion beam.