An Efficient Vircator With High Output Power and Less Drifting Electron Loss by Forming Multivirtual Cathodes

Choi

2022

Electronics

Self Cite

A virtual cathode oscillator or vircator is a vacuum tube for producing high-power microwaves (HPM). The efficiency of the vircator has been a difficult task for decades. The main reasons for low efficiency are intense relativistic electron beam (IREB) loss and few or no interactions between IREB and HPM. In this case, forming multiple virtual cathodes may be beneficial in overcoming these constraints. By reusing the axially propagating leaked electrons (LE), we could confine them and form multiple virtual cathodes (VCs). This article discussed the characteristics of newly formed VCs based on simulation results. The formation time of new VCs was discovered to be highly dependent on the reflector position and the density of LE approaching their surfaces. Furthermore, multiple VC formation in the waveguide region does not affect conventional VCs’ position or forming time. The emission mode of the generated HPM was TM01 with single and multiple VCs and remained unaffected. The formation of multiple VCs positively influenced the axial and radial electric fields. When compared to a single VC, the axial and radial electric field increased 25.5 and 18 times with multiple VCs. The findings suggested that forming multiple VCs could be a future hope for achieving high vircator efficiency.

Section: Discussionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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The Characteristics of the Second and Third Virtual Cathodes in an Axial Vircator for the Generation of High-Power Microwaves

Choi

2022

Electronics

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“…This window also allowed the produced HPM to propagate outside of the guiding tube, preventing surface breakdown. In our earlier work, the mechanisms by which Chundoong produces HPM were extensively described (Mumtaz et al, 2022b;Mumtaz and Choi, 2022). B-dot probe was used to measure current in the vacuum diode region, and C-dot probe was used to measure voltage in the pulse forming line region.…”

Section: Pulsed Hpm Generator and Experimental Detailsmentioning

confidence: 99%

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

Rana

Choi

et al. 2023

Front. Cell Dev. Biol.

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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 3.5 GHz HPM on brain normal astrocytes and cancer U87 MG cells, as well as the likely mechanisms involved.Methods: To generate 3.5 GHz 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 (1 mJ/pulse), with each pulse delivered after 1 min of charging time to evaluate the dose dependent effects.Results: A strong electric field (∼23 kV/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.

“…For the decontamination of various virus species, a variety of physical approaches have been used, including electromagnetic irradiation, X-rays, UV, and gamma radiations [ 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 ]. Many radiation sources exist, and radiation production is an ongoing subject of study [ 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 ] that is beneficial to facilitate our modern lives. Figure 6 graphically depicts the direct impact and mechanism of employing radiations to disinfect microorganisms.…”

Section: Virus Deactivation By Radiationmentioning

confidence: 99%

Review of Developments in Combating COVID-19 by Vaccines, Inhibitors, Radiations, and Nonthermal Plasma

Han

Srinivasan

et al. 2022

CIMB

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Global society has been highly pressured by the COVID-19 pandemic, which has exposed vulnerabilities in supply chains for disinfection products, personal protective equipment, and medical resources worldwide. It is critically necessary to find effective treatments and medications for these viral infections. This review summarizes and emphasizes critical features of recent breakthroughs in vaccines, inhibitors, radiations, and innovative nonthermal atmospheric plasma (NTAP) technologies to inactivate COVID-19. NTAP has emerged as an effective, efficient, and safe method of viral inactivation. NTAP can be used to inactivate viruses in an environmentally friendly manner, as well as activate animal and plant viruses in a variety of matrices. Researchers and engineers desire to help the medical world deal with the ongoing COVID-19 epidemic by establishing techniques that make use of widely available NTAP technologies. NTAP technology is not dependent on viral strain, and it does not necessitate months or years of research to develop specific vaccines for each novel or arising viral disease. We believe the NTAP is a highly promising technique for combating COVID-19 and other viruses. Thus, NTAP technology could be a significant breakthrough in the near future in assisting humans in combating COVID-19 infections. We hope that this review provides a platform for readers to examine the progress made in the fight against COVID-19 through the use of vaccines, inhibitors, radiation, and NTAP.