High-power Microwave Radiation Research Articles

Benefits of Microwave-Assisted Heat Treatment for Sintered Diopside Glass-Ceramics.

Sinter-crystallization is a specific method of producing glass-ceramics that allows the manufacture of complexly shaped products, composites and solder. However, it usually is limited when the glass powders used are characterized by a high crystallization trend. This study proposes a new opportunity to improve the sinter-crystallization and demonstrates the benefits of microwave processing using diopside (CaMg(Si2O6)) glass-ceramics with an enhanced crystallinity of ~70%. The advantages of microwave processing are shown by comparing the results obtained with scanning electron microscopy, X-ray computed tomography and gas pycnometry for two glass-ceramic specimens. The first sample is obtained in the heat resistant furnace of an optical dilatometer, while the second is obtained by heating it with high-power microwave irradiation at 2.45 GHz, 1kW. Intense crystallization was observed in the sample sintered in an electric furnace, which blocked the sintering process and resulted in significant open porosity (7.1%). In addition, closed pores caused by the crystallization are observed in the centers of the sintered particles (5.2%). At the same time, the overall porosity of the microwave-sintered glass-ceramic is reduced by about two times, and the open porosity is practically eliminated (0.5%). In this sample, together with the crystallization-induced pores, some residual closed spherical pores, typical for a well-sintered sample, are also observed.

Modeling of 2-D Periodic Array of Dielectric Bars with a Low Reflection Angle for a Wind Tunnel High-Power Microwave Experiment

Two-dimensional periodic dielectric bars have potential applications in high-power microwave (HPM) radiation effect experiments performed in wind tunnels. Such a bar is designed to consist of two types of dielectric materials, and two lined-up blocks can be considered as a period along the bar. Under plane excitation, the theoretical period length of the beat wave pattern fits well with the simulation result, which requires modifying the previously presented field-matching method. The phase distribution on the cross-section can be non-uniform when two different guiding modes are excited independently and propagate along different materials. Directional reflection with a low reflection angle can be obtained by reasonably choosing the parameters of the dielectric array. The designed array can decrease the returned-back microwave power toward the microwave source by 6 dB according to the numerical simulation, which included the wind tunnel, the input antenna, the test target, and the reflect array in one model.

Modeling of the characteristics of an avalanche photodiode taking into account the influence of the directed energy of the electromagnetic field

The paper presents and discusses the results of simulation of the current-voltage characteristics of an avalanche photodiode carried out in the SPICE program. The simulations take into account the influence of the directed energy of the electromagnetic field used in modern DEW (Directed-Energy Weapon), in the form of laser optical radiation and HPM (High Power Microwave) radiation, on the characteristics of the photodiode. The calculations were made using the model of the considered diode developed by the authors.

Pulsed high power microwave seeds priming modulates germination, growth, redox homeostasis, and hormonal shifts in barley for improved seedling growth: Unleashing the molecular dynamics

Increasing the seed germination potential and seedling growth rates play a pivotal role in increasing overall crop productivity. Seed germination and early vegetative (seedling) growth are critical developmental stages in plants. High-power microwave (HPM) technology has facilitated both the emergence of novel applications and improvements to existing in agriculture. The implications of pulsed HPM on agriculture remain unexplored. In this study, we have investigated the effects of pulsed HPM exposure on barley germination and seedling growth, elucidating the plausible underlying mechanisms. Barley seeds underwent direct HPM irradiation, with 60 pulses by 2.04 mJ/pulse, across three distinct irradiation settings: dry, submerged in deionized (DI) water, and submerged in DI water one day before exposure. Seed germination significantly increased in all HPM-treated groups, where the HPM-dry group exhibited a notable increase, with a 2.48-fold rise at day 2 and a 1.9-fold increment at day 3. Similarly, all HPM-treated groups displayed significant enhancements in water uptake, and seedling growth (weight and length), as well as elevated levels of chlorophyll, carotenoids, and total soluble protein content. The obtained results indicate that when comparing three irradiation setting, HPM-dry showed the most promising effects. Condition HPM seed treatment increases the level of reactive species within the barley seedlings, thereby modulating plant biochemistry, physiology, and different cellular signaling cascades via induced enzymatic activities. Notably, the markers associated with plant growth are upregulated and growth inhibitory markers are downregulated post-HPM exposure. Under optimal HPM-dry treatment, auxin (IAA) levels increased threefold, while ABA levels decreased by up to 65 %. These molecular findings illuminate the intricate regulatory mechanisms governing phenotypic changes in barley seedlings subjected to HPM treatment. The results of this study might play a key role to understand molecular mechanisms after pulsed-HPM irradiation of seeds, contributing significantly to address the global need of sustainable crop yield.

Annular Beam Driven Metamaterial Backward Wave Oscillator

Metamaterials (MTMs) are synthetic materials designed to have characteristics that "may not be readily available in nature," such as negative permittivity, reversed Doppler Effect, reversed Cherenkov Effect, and negative Refractive Index. These characteristics have motivated researchers to analyze and investigate the use of MTMs for modelling high-power microwave (HPM) radiation sources. One of the most potential HPM sources is an annular beam-driven Backward-Wave Oscillator (BWO) based on the Cerenkov mechanism. The devices that use the Cerenkov mechanism are preferred due to their larger bandwidth. Its high output power and repetition operations make it a promising source. In this paper, an annular beam-loaded metamaterial BWO is simulated in order to investigate and comment on the possibility of metamaterial or metamaterial-inspired structures replacing the slow-wave structures (SWSs) in vacuum tube devices. Performance parameters of several BWO configurations loaded with different metamaterial-inspired conductor rings are compared to rippled SWS-based BWOs. The results suggest that fewer metamaterial rings with solid cross-section (CS) inside the BWO lead to a closer match in generated output power and frequency with the output power generated using a rippled SWS.

High-power Broadband Reflectarray Antenna with Height Adjustment

To enhance the power capacity and bandwidth of antenna arrays, a high-power broadband reflectarray antenna with height adjustment has been proposed. The high-power reflectarray comprises reflective elements, a beam scanning control system, and a high-power feed source. In the design, the high-power feed source horn radiates GW-level high-power microwave radiation onto the reflective elements, which adjust their relative height through the beam scanning control system to compensate for phase shifts, enabling the beam to be steered in any direction. The reflective elements utilize a novel total internal reflection form, offering a simple structure that ensures the power capacity and aperture efficiency, as well as bandwidth of the antenna array. Full-wave simulation results demonstrate that this phased array can achieve a 360° phase shift, two-dimensional ±50° beam scanning, an aperture efficiency of 81%, a -1dB bandwidth of 10.8%, and a power capacity of 14GW.

High-power Microwaves Against Locust Invasion

Background:: There are a lot of phytophagous and harmful animals in agriculture and forestry in the entire world. The ultimate goal in locust control is the use of preventive and proactive methods that disrupt the environment to the least possible extent. This would make agricultural production easier and more secure in the many regions where growing crops is of vital importance. Method:: The possibility of using high-power microwave systems to combat harmful animal pests in agriculture and forestry is discussed. The proposed method is compared favorably with respect to the environment. Results:: The obtained results of the study demonstrated the possibility of using modern sources of high-power microwave radiation to solve the problem of insect invasion. Conclusion:: It should be noted that the use of powerful microwaves is a promising means of controlling locusts and other pests. Mobile international forces equipped with modern microwave apparatus can solve the problem of combating locusts and other pests on a global scale without harming the environment. Microwave systems can also be used against other phytophagous pests of agriculture and forestry.

An open-end high-power microwave-induced fracturing system for hard rock

Microwave pre-treatment is considered as a promising technique for alleviating cutter wear. This paper introduces a high-power microwave-induced fracturing system for hard rock. The test system consists of a high-power microwave subsystem (100 kW), a true triaxial testing machine, a dynamic monitoring subsystem, and an electromagnetic shielding subsystem. It can realize rapid microwave-induced fracturing, intelligent tuning of impedance, dynamic feedback under strong microwave fields, and active control of microwave parameters by addressing the following issues: the instability and insecurity of the system, the discharge breakdown between coaxial lines during high-power microwave output, and a lack of feedback of rock-microwave response. In this study, microwave-induced surface and borehole fracturing tests under true triaxial stress were carried out. Experimental comparisons imply that high-power microwave irradiation can reduce the fracturing time of hard rock and that the fracture range (160 mm) of a 915-MHz microwave source is about three times that of 2.45 GHz. After microwave-induced borehole fracturing, many tensile cracks occur on the rock surface and in the borehole: the maximum reduction of the P-wave velocity is 12.8%. The test results show that a high-power microwave source of 915 MHz is more conducive to assisting mechanical rock breaking and destressing. The system can promote the development of microwave-assisted rock breaking equipment.

Analysis of Low-Frequency Communication of Hypersonic Vehicles in Thermodynamic and Chemical Non-Equilibrium State

A plasma sheath will be developed surrounding a hypersonic vehicle in flight, which can reflect, absorb, and scatter electromagnetic (EM) waves of lower frequencies than its own, resulting in a communication blackout. This paper focuses on knowing how to limit the absorption and reflection of low-frequency EM waves by plasma sheath in a thermodynamic and chemical non-equilibrium state. According to the temperature increment model, the energy of high-power microwave (HPM) irradiation is translated into the temperature increment of heavy particles in plasma. As a result of this modification process, the transmittance of low-frequency EM waves going through the plasma sheath in a certain time frame rises, potentially easing the communication blackout problem.

Structure of Fluctuations in the Edge Plasma of a Stellarator in Modes with Transport Transitions

The evolution of fluctuating signals from electrostatic and magnetic probes and reflectometry on the L-2M stellarator is presented. The L-2M facility is a quasi-stationary toroidal magnetic trap in which plasma is generated and heated by high-power pulsed microwave radiation. Pulses with transitions to improved confinement modes accompanied by an increase in energy, increase in plasma density, and restructuring of the peripheral electric field, were analyzed. Spectral analysis of signals is carried out using Fourier analysis and various wavelets. The possible influence of magnetohydrodynamic and kinetic instabilities on the development of transient processes is considered.

Structure of Fluctuations in the Edge Plasma of a Stellarator in Modes with Transport Transitions

The evolution of fluctuating signals from electrostatic and magnetic probes and reflectometry on the L-2M stellarator is presented. The L-2M facility is a quasi-stationary toroidal magnetic trap in which plasma is generated and heated by high-power pulsed microwave radiation. Pulses with transitions to improved confinement modes accompanied by an increase in energy, increase in plasma density, and restructuring of the peripheral electric field, were analyzed. Spectral analysis of signals is carried out using Fourier analysis and various wavelets. The possible influence of magnetohydrodynamic and kinetic instabilities on the development of transient processes is considered.

High-Power Microwave Pulse-Induced Failure on Unmanned Aerial Vehicle System

With the wide application of unmanned aerial vehicles (UAVs), more attention has been paid to the safe operation of UAVs in complex electromagnetic environments. In this article, we investigate the impact of high-power microwave (HPM) pulses on three types of typical commercial UAVs. We established the HPM irradiation experiment system first and obtained the responses of UAVs under the HPM attack with different electric field strengths. The flight logs and the damage analysis reports indicate that the damaged components of the type I UAV and the type II UAV are the rotor motor and the electronic speed controller. The experiment results prove that L-band narrowband HPM microwave has strong backdoor coupling effects on UAVs. The damage mechanism of UAVs by the HPM is studied by simulation. The simulation results show that an HPM pulse will cause a high-voltage pulse coupled to the cable connecting the electronic speed controller and the rotor motor, which caused the electronic speed controller to send out a false signal that caused the rotor motor speed to rise sharply, eventually making the rotor motor to burn out. Experiment results show that strengthening electromagnetic protection on the cable can effectively prevent HPM damage to UAVs. The simulation results match the experiment results and the damage analysis reports. Finally, some suggestions are provided to improve the UAV’s anti-HPM capability.

Microwave-aided pyrolysis and fragmentation of tar-rich coal and rocks for in situ coal conversion and clean utilization

British Petroleum predicts that coal will account for the largest share in energy resources for power generation until 2040. The U.S. Energy Information Administration forecasts that coal will remain a key component of the country's national electricity portfolio at least until 2040. However, due to serious issues including high carbon emissions, environmental pollution, surface subsidence, resource wastage, and mining accidents associated with traditional coal mining and utilization patterns, international communities have called for the abandonment of coal use and adoption of renewable resources. To overcome the disadvantages, we proposed a novel approach for achieving in situ conversion and power generation using subsurface coal. An earthworm-shaped intelligent unmanned mining machine (IUMM) was designed to use high-power microwave energy to pulverize and pyrolyze coal into particles that can be used for power generation via chemical conversion. In this study, we used IUMM-based technology for in situ conversion and utilization of tar-rich coal and recovery of oil and gas from the coal. We quantified the pyrolysis efficiency of the tar-rich coal and the surrounding sandstone as well as the gas–liquid overflow rate of the coal under various high-power microwave irradiation conditions. The critical microwave energy threshold for discriminating tar-rich coal from the surrounding sandstone was determined, which will help to realise automatic pyrolysis of tar-rich coal by IUMM and minimise the damage caused by high-energy microwave radiation to the surrounding rock. This work aids in the production of cleaner energy, while ensuring energy security.

ROS production in response to high-power microwave pulses induces p53 activation and DNA damage in brain cells: Radiosensitivity and biological dosimetry evaluation.

Background: Pulsed high-power microwave (HPM) has many applications and is constantly being researched to expand its uses in the future. As the number of applications grows, the biological effects and safety level of pulsed HPM become a serious issue, requiring further research. Objective: The brain is regarded as the most vulnerable organ to radiation, raising concerns about determining an acceptable level of exposure. The effect of nanosecond pulses and the mechanisms underlying HPM on the brain has not been studied. For the first time, we observed the effect of pulsed 3.5GHz HPM on brain normal astrocytes and cancer U87 MG cells, as well as the likely mechanisms involved. Methods: To generate 3.5GHz HPM, an axial virtual cathode oscillator was constructed on pulsed power generator "Chundoong". The cells were directly exposed to HPM (10, 25, 40, and 60) pulses (1mJ/pulse), with each pulse delivered after 1min of charging time to evaluate the dose dependent effects. Results: A strong electric field (∼23kV/cm) of HPM irradiation primarily causes the production of reactive oxygen species (ROS), altering cell viability, mitochondrial activity, and cell death rates in U87 and astrocytes at certain dosages. The ROS generation in response to HPM exposure was primarily responsible for DNA damage and p53 activation. The hazardous dosage of 60 pulses is acknowledged as having damaging effects on brain normal cells. Interestingly, the particular 25 pulses exhibited therapeutic effects on U87 cells via p53, Bax, and Caspase-3 activation. Conclusion: HPM pulses induced apoptosis-related events such as ROS burst and increased oxidative DNA damage at higher dosages in normal cells and specific 25 pulses in cancer U87. These findings are useful to understand the physiological mechanisms driving HPM-induced cell death, as well as the safety threshold range for HPM exposure on normal cells and therapeutic effects on cancer U87. As HPM technology advances, we believe this study is timely and will benefit humanity and future research.

Design and Cold Test on the Slow Wave Structure of a Wide-Voltage Tuned and High-Power Extended Interaction Oscillator in W-Band

In order to obtain continuously tunable high-power output 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, the slow wave structure (SWS) of a wide tuned and high-power extended interaction oscillator (EIO) was designed and studied in this article. The structure of the designed circuit was described while the operating characteristics were analyzed. The SWS not only has high power output capability but also operates near standing waves with a wide electronic tuning range. The EIO can operate over an electronic tuning range of 1.36 GHz in ensuring the output power no less than 1.6 kW, where the maximum output power over 4.5 kW is obtained at 43.8 kV and 2 A from the simulation. The wide tuning range and the high output power are achieved by increasing the number of periods with offsetting the coupling hole and beam voltage and current in order to match with high impedance modes near to 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi $</tex-math> </inline-formula> . The SWS was processed and cold tested, and its S-parameter distribution was close to the simulation result. The designed 94-GHz extended interaction oscillation can be effectively used to generate wide tuned and high-power microwave radiation sources in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$W$</tex-math> </inline-formula> -band.

Simulation study of alleviating the communication blackout using high-power microwave irradiating plasma sheaths

During hypersonic vehicle flight at high speed, plasma sheath on the vehicle surface will attenuate or even interrupt the communication signal, leading to the “communication blackout” problem. The vehicle probably moves a long distance during the communication blackout due to its high speed, which is a serious threat to the safety of the vehicle. This paper proposes a method to solve the communication blackout problem using high-power microwave (HPM) irradiation. The multicomponent compressible model, finite difference time domain algorithm, and multi-fluid model are used to simulate the interaction between HPM and plasma sheath. The results show that after HPM irradiation, the electromagnetic (EM) wave transmissivity of the plasma sheath will change, and the electric field (E-field) amplitude and irradiation time of HPM significantly influence the change of transmissivity. Thereafter, analyses of the changes of the collision and plasma frequencies of the plasma sheath after HPM irradiation showed the transmissivity of the plasma sheath to low-frequency EM waves is improved by optimizing E-field amplitude and irradiation time of HPM. Therefore, HPM irradiation can be performed to enhance the transmissivity of the plasma sheath to the communication signal, thus alleviating the communication blackout problem.

A wideband high-power microwave radiation source based on gyromagnetic nonlinear transmission line and Vlasov antenna.

The gyromagnetic nonlinear transmission line (GNLTL) is a special kind of coaxial transmission line partially loaded with the ferrite material. A GNLTL system can modulate the input high-power pulses into wideband high-power microwaves without relying on the electron beam and confining magnetic field. The unique working mechanism gives the GNLTL system the potential to be a small portable wideband high-power microwave radiation source. In this study, a wideband high-power microwave radiation source based on a GNLTL system is designed and constructed. In order to effectively radiate the wideband microwaves into the air, a high-power wideband Vlasov antenna and a special absorption high-pass filter are developed. The designs of key subsystems and high-power radiation experiments have been introduced and discussed in detail. In the test experiments, a radiated pulse with a peak electric field strength of 23 kV/m was measured at 20m away from the transmitting antenna and the effective potential of radiation is 460 kV/m. The pulse width of the radiation pulse is about 4ns, the center frequency is about 2.25GHz, and the highest repetition rate can reach 25Hz.

Investigation on Falling and Damage Mechanisms of UAV Illuminated by HPM Pulses

Unmanned aerial vehicle (UAV), when illuminated by high-power microwave (HPM), is vulnerable to losing control and even falling to the ground with damage. To explore the mechanism of the UAV's falling and its damage caused by HPM, the HPM radiation experiments on a certain kind of UAV are carried out. It is concluded that the UAV's cable is the main energy coupling path from HPM according to the analysis of the cable connection relationships among the flight control system (FCS), the electronic speed control (ESC) board, and the motors based on the experiment. Furthermore, the coupled voltages of the cable's termination load are obtained when the UAV is radiated by HPM with different carrier frequencies or incident directions using numerical calculation and typical test verification. To facilitate the analysis of circuit level, the equivalence of radiation and injection test is analyzed, so the waveform of the control signal related to the UAV's flight is recorded by the injection test. According to the experimental results and the principle of the UAV's flight dynamics, the effect mechanisms of the UAV's falling and its damage are clarified. The experimental results show that the carrier frequency of the HPM leading to the falling and damage of the UAV mainly depends on the length of the internal cable inside the UAV. The pulsewidth and the repetition frequency of HPM resulting in the UAV's falling are related to the pulsewidth and the period of the control signal of FCS. In addition, the coupled voltages induced on the twisted three-wire cables due to the illumination of HPM are verified to enter into the control signal port through parasitic capacitance and, finally, to damage the vulnerable components, including the metal–oxide–semiconductor field-effect transistor inside the ESC and the motor of the UAV. The damage mechanism is determined to be the high-voltage breakdown and large current burning.

Effects of high-power microwave irradiation on tar-rich coal for realising in situ pyrolysis, fragmentation, and low-carbon utilisation of tar-rich coal

Tar-rich coal was directly combusted during power generation, resulting in a huge waste of precious oil resources and a large amount of carbon emissions . The idea of intelligent unmanned mining machine (IUMM) for in-situ fluidised mining and conversion of tar-rich coal was proposed to solve the problems of traditional mining and utilisation methods, realise efficient utilisation of tar-rich coal, and achieve net-zero CO 2 emission. A key technology of IUMM is the pyrolysis and fragmentation of tar-rich coal by high-power microwave irradiation . In this study, we carried out experiments on the strength and microstructural changes of tar-rich coal under different microwave irradiation conditions using the high-power microwave irradiation testing system to explore the effects of microwave irradiation on tar-rich coal and provide a reference for the design of IUMM. The X-ray computed tomography was employed to observe and characterize the initiation, growth, connection, and spatial distribution of internal fractures of tar-rich coal under different microwave irradiation conditions. The quantitative relationship between the strength characteristics of tar-rich coal and microwave irradiation conditions was established. The results show that under a fixed microwave power or irradiation time, the overflow rate of coal gas and tar is linearly positively correlated with microwave energy E , and both the uniaxial compressive strength and brittleness of tar-rich coal have piecewise linear negative correlation with E . With the increase of E , the internal fractures grow and connect more, which are synchronised with the decrease of the uniaxial compressive strength and elastic modulus of the tar-rich coal. With equal E input, high-power microwave has a more significant effect on strength weakening, fracturing, and fragmentation of tar-rich coal. Our findings can be used for the subsequent implementation of in-situ pyrolysis and fragmentation technology of IUMM for realising the in-situ conversion, high-efficiency utilisation, and low carbon emissions of tar-rich coal.

Evolution of pore-fracture structure and permeability of coal by microwave irradiation under uniaxial compression

In a natural coal reservoir environment, the coal seam is constrained by in-situ stress and gas pressure. Damage on the coal microstructure due to microwave irradiation (MI) differs significantly different from that under no-load conditions. In this study, the effect of MI on the pore-fracture structure and seepage characteristics of load-constrained coal is investigated using a custom-developed microwave fracturing experimental device, nuclear magnetic resonance test device, and permeability test device. Based on the relationship between microwave and pore-fracture structure parameters and the permeability of loaded coal, the pore-fracture structure evolution and permeability growth law of loaded coal under MI are determined. The results show that the number of micropores in coal decreases and the T2 curve of micropores is shifted to the right under the combined effect of MI and external stress load. The numbers of mesopores, macro-pores, and micro-fractures increase, and the T2 curve exhibits a broader peak span. The pore-fracture structure evolution effect of loaded coal increases with the microwave power and MI time. Under high-power MI, the pore-fracture structure evolution of the loaded coal shows a “decrease - increase – decrease” trend as the stress load increases, whereas a “decrease – increase” trend is shown under low-power MI. Under the same microwave parameters, the permeability of unloaded and loaded coal increases by a maximum of 15.7 and 364.7 times, respectively. In particular, the permeability increases by 3.1–11.4 and 17.8–49.7 times under external stress loads of 4 and 2 MPa, respectively. The combination of high MI power and short MI duration under the same microwave energy facilitates the development of the pore-fracture structure and increases the permeability of loaded coal. Microwaves have a differential thermal effect on mineral in coal, which reduce the physical properties of the coal. Pore-fracture structure and permeability are further enhanced by the stress load.