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An efficient and short synthesis of fused dihydroisoquinolines, diaryl substituted pyridine derivatives in good to high yields has been established by using an environmentally safe, solvent‐metal‐oxidant‐free tandem approach. In this article, we discuss how the electrocyclic reaction is more pronounced in the solid phase in the presence of urea, whereas the typical aza‐Michael addition is more prominent in presence of arylamine in the solution phase for 3‐(2‐formylcycloalkenyl)acrylic ester derivative substrates. The wide range of substrates and urea‐promoted neat synthesis made our approach more significant in medical and also analytical science. Moreover, an isoquinoline alkaloid decumbenine B analogue has been synthesized by using our newly developed neat methodology. We have also investigated the photophysical properties of the synthesized fused dihydroisoquinoline derivatives. One of the synthesized molecules was used as a sensor for the selective detection of toxic picric acid. Therefore, the effective neat synthesis and molecular sensing applications of these compounds made our approach more exciting in the field of heterocyclic chemistry. [ABSTRACT FROM AUTHOR]

Ammonium thiocyanate-promoted simple, rapid and eco-friendly neat synthesis of isothiazoles is developed for the first time. It is noteworthy that an instantaneous valuable synthetic route of β-enaminones is also documented during the mechanistic investigation of isothiazole formation. A detailed mechanistic explanation of the isothiazole formation reaction is clearly explained by the control experiments. NBS-promoted aromatisation of isothiazole derivatives and photophysical properties of an isothiazole-pyrene hybrid molecule have been investigated. [ABSTRACT FROM AUTHOR]

The current study describes an efficient environmental benign synthetic route of N-aryl substituted c-fused pyrrole derivatives via neat approach. It also provides base-mediated intramolecular macrolactamization using amine ester amidation reaction and leads to fused diazocine-6(5H)-one with effective yields. [ABSTRACT FROM AUTHOR]

Herein, we report one‐pot Cu(I) catalyzed open flask synthetic strategy of 3‐substituted N‐pyridinyl isoindolinones from alkyl (E)‐3‐(2‐formylphenyl)acrylate by oxidative amidation and intramolecular aza‐Michael reaction using cheap air stable Cu(I) single catalyst. We have also established a synthetic route of N‐aryl substituted isoindolinones with acid‐amine coupling reaction of (E)‐2‐(3‐alkoxy‐3‐oxoprop‐1‐en‐1‐yl)benzoic acid followed by aza‐Michael reactions. Unexpected synthetic route of N‐(1H‐inden‐1‐yl)pyridin‐2‐amine derivatives have been documented from the same precursors using Cu(I) catalyst. [ABSTRACT FROM AUTHOR]

This article presents the design and analysis of a staggered double-vane (SDV) slow-wave structure (SWS) for $W$ -band amplifier, with 20-dB gain and a very high bandwidth (~25%). The use of dual Bragg reflector at either end of the interaction structure increases the impedance matching and the radio frequency (RF) coupling efficiency at the input and output ports, thereby reducing the RF leakage at the electron gun and collector ends, from 15% to 25% to less than 0.6%. The attenuator section is simple to fabricate and optimally designed in order to provide an effective isolation (>20 dB) between the input RF signal in the input section and the RF signal reflected from the output section. The dispersion analysis, the transmission analysis of each section, and the beam–wave interactions were simulated using the Dassault system’s computer simulation technology (CST) eigenmode solver, time-domain solver, and the particle-in-cell (PIC) solver, respectively. The proposed design of the SDV SWS conclusively provides an enormous bandwidth of ~25 GHz with 20-dB gain for $W$ -band amplifier, when compared to its solid-state counterparts and earlier reported work as per the author’s knowledge. [ABSTRACT FROM AUTHOR]

The coaxial interaction structure for a 0.24-THz, 2-MW gyrotron is designed, and its RF behavior is analyzed for the beam current of 60 A and the beam voltage of 90 kV. The searching of a suitable, very high-order TE mode, which satisfies all the technical conditions required to generate 2-MW RF power, is an important and critical step in the development of a coaxial-cavity (COCA) gyrotron. The detailed analysis of mode selection is described in this article. The geometry of the axially corrugated insert is optimized using an in-house code COCA. Based on the optimized geometry of the coaxial insert and the cylindrical cavity, the coupling coefficient and the start oscillation current are computed to analyze the mode competition for the operating mode TE42,28. The particle-in-cell (PIC) algorithm-based simulation tool is used for the beam–wave interaction computation. Very fine meshing is implemented in the simulations, considering the high frequency and fine geometry of the coaxial insert. The electron beam parameters and the cavity magnetic field are optimized first aiming at the RF power ≥2 MW and frequency 240 GHz. The final results of the cavity design confirm 2.2-MW RF power and 239.975-GHz frequency at 9.74-T magnetic field. [ABSTRACT FROM AUTHOR]

Herein we report an unprecedented functional group assisted decarboalkoxymethylation (–CH2CO2R) of N‐pyridinyl pyrrolo esters by using air stable and cheap copper(I) catalyst. 2‐formyl substituent of pyrrole unit is the key isolated intermediate for this novel transformation. This methodology is quick and tolerates a wide range of functional groups in open flask conditions. This protocol provides a large array of tricyclic N‐pyridinyl 2, 5 unsubstituted fused pyrrole derivatives with high yield (up to 92 %). [ABSTRACT FROM AUTHOR]

An easy green synthetic approach for fused isoindoloquinazolinones has been developed under neat reaction (yields up to 91%) conditions. This new one-pot tandem methodology involves condensation of readily available anthranilamide with 3-(2-formylcycloalkenyl)-acrylic ester under solvent- and catalyst-free conditions. This strategy avoids the use of oxidant, and heavy metal catalysts and also is free from work-up and generation of toxic by-products. A dramatic change of photophysical properties of dihydroisoindoloquinazolinones in basic and aqueous media has also been documented in our study. Moreover, our model synthetic compound shows cytotoxic activity towards metastatic HepG2 and PC3 cancer cell lines. [ABSTRACT FROM AUTHOR]

A 42-GHz, 200-kW gyrotron was developed and tested for the Indian plasma fusion system. The gyrotron was designed for the TE0,3 operating mode. The configuration of the triode-type magnetron injection gun (MIG) with the linear RF output, undepressed collector, and face-cooled double disk window was adopted in this gyrotron because of the first development experience. The complete tube was developed and processed at Central Electronics Engineering Research Institute (CEERI), Pilani, India. The RF testing of the gyrotron was performed at the participating institute, Institute of Plasma Research (IPR), Gandhinagar, India. Due to some cooling issues in the collector region, the tube was tested by a resistive capacitor network-based power supply for a very short pulse in place of a long pulse, high voltage power supply. The tube was tested up to the beam voltage of 51 kV and a beam current of 12 A at the cavity magnetic field of 1.61 T for the short pulse of $500~\mu \text{s}$. The tube was inserted into the magnet system consisting of a main electromagnet, auxiliary gun coils, and collector magnets. The multi-hole and single hole couplers were used to measure the RF power in the TE0,3 mode and the overall power, respectively. The measured results were also compared with the simulated results and a close agreement of the results was found. The short pulse testing confirms the electrical design and the development approach for the 42-GHz gyrotron tube. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach for computation of high-order axial modes (HOAMs) in a conventional and uptapered gyrotron resonator. A code has been developed which computes the eigenfrequency, Q-factor and axial field profile of HOAMs in the absence of electron beam in the resonator. Cyclic coordinate search method has been used for the optimization of complex eigenfrequencies, which obviates the computation of gradients of radiation boundary conditions and, hence, reduces computational complexity. HOAMs have been computed for resonators operating at 10, 132, 203, and 424 GHz, and the results obtained have been found to be in good quantitative agreement with the experimental and numerical data available in the published literature. Broadband continuous frequency tuning bandwidth found for subterahertz resonators also agrees well with the published results. HOAMs computed for 1-THz gyrotron resonator designed at CSIR-CEERI have also been presented. [ABSTRACT FROM AUTHOR]

Total synthesis of the pentasaccharide repeating unit of the exopolysaccharide from Lactobacillus rhamnosus BIM B-1039 is accomplished by bis-glycosylation on a suitably protected trisaccharide di-ol. The stereochemically challenging β-D-ManNAc residue was introduced through a glucose derivative to ensure β-selectivity followed by inversion of the 2-OH position with azido group to form the desired mannosamine moiety. The use of the p -methoxyphenyl glycoside at the reducing end was triggered by the fact that its oxidative cleavage followed by the formation of the trichloroacetimidate derivative will open up the scope for further conjugation of suitable aglycon. [Display omitted] • Total chemical synthesis of the tetrasaccharide repeating unit of the O-antigent from Lactobacillus rhamnosus BIM B-1039. • Incorporation of challenging β-D-ManNAc unit in the oligosaccharide. • Potential vaccine designing. [ABSTRACT FROM AUTHOR]

Thermal analysis of an L-band 60-kW (continuous-wave) double-ring strapped magnetron for optimizing the design of a cathode support structure and cooling system is presented. This magnetron consists of an oxygen-free copper anode with ten built-in cooling channels and a directly heated tungsten cathode. The operating temperature of the cathode is greater than 2000 ^\circ\C; therefore, proper thermal design of the cathode support structure is essential for reliable operation. The heat convection coefficient for the forced air is estimated by simulations comparing the simulated temperatures for different heat convection coefficients with the measured one. It is observed that the comparison between simulations with measurement is in good agreement for various temperatures from 1000 ^\circ\C to 2000 ^\circ\C when the estimated heat convection coefficient of the forced air is used. [ABSTRACT FROM AUTHOR]

A helix slow-wave structure (SWS) for a high-efficiency (electronic efficiency > 25%) Ku-band 140-W space traveling-wave tube (TWT) has been designed. The cold circuit parameters of helix SWS, like propagation constant and on-axis interaction impedance, were determined using 3-D electromagnetic field simulators ANSOFT-HFSS and CST-MWS, and those were validated with the experimental results. The in-house developed large-signal code SUNRAY-1D was used to design a complete helix SWS in two sections with sever and taper to achieve desired output power, gain, efficiency, and other linearity parameters like phase shift, AM/PM factor, and I/M components. The simulated RF performance of the Ku-band 140-W helix TWT was validated with the experimental results. A close agreement between the simulated and experimental results has been found. [ABSTRACT FROM PUBLISHER]

The article presents a study which designed a triode-type magnetron injection gun of a 42-gigahert, 200-kilowatt gyrotron for an Indian TOKAMAK system by applying the code EGUN. The gyrotron is an instrument that can produce high powers at very high frequencies. The estimations are carried out to calculate the parameters connected to the cathode, the magnetic field, and the modulating anode voltage. The study is accomplished with the validation of the design by utilizing another code TRAK.

In this paper, a synthesized design of the magnetron injection gun (MIG) for a 200 kW, 42 GHz gyrotron is presented. The synthesis steps involve the selection of the type of the MIG, the development of the design criteria, the selection of initial design parameters and the development of a program for the estimation of the synthesized parameters for the MIG design. The presented approach estimates the cathode, the beam and the anode parameters, enabling one to build a synthesis model of a complete MIG system. [ABSTRACT FROM AUTHOR]

Chemical synthesis of the tetrasaccharide repeating unit of the O -antigen from E. coli O74 is accomplished by a convergent [2 + 2] block synthesis strategy. The challenging rare D-Fuc3NAc has been prepared using DTBP and TIPST mediated deoxygenation reaction. Other monosaccharide synthons are prepared through rational protecting group manipulations and the stereoselective glycosylations are achieved either by the activation of thioglycoside or glycosyl trichloroacetimidate. The target tetrasaccharide is made in the form of its 2-aminoethyl glycoside to facilitate further glycoconjugate formation without affecting the anomeric stereochemistry. [Display omitted] • Total chemical synthesis of the tetrasaccharide repeating unit of the O-antigent from E. coli O74. • Synthesis of rare D-Fuc3NAc derivative and incorporation in oligosaccharide. • Deoxygenation reaction with DTBP and TIPST. • Potential vaccine designing. [ABSTRACT FROM AUTHOR]

Isoindolinones are the core structures of many natural products and drug molecules and are useful in materials science as fluorescent probes and synthetic dyes. The fused analogues of these blended lactams also have a wide range of applications in medicinal chemistry and chemical biology. Different synthetic approaches and the use of versatile reagents have been reported for the synthesis of these novel molecules. Different research groups have focused their efforts on improving synthetic protocols towards the synthesis of the isoindolinone frame both in the presence and absence of transition metals. However, the transition metal-based pathway requires hazardous conditions, which are toxic to the environment. In particular, the transition metal-free synthetic protocols for isoindolinones and their fused analogues are highly fascinating due to several advantages for the industrial production of these bio-active molecules. These concepts encouraged us to write this review to highlight the recent advancements in the synthetic methods involving transition-metal-free approaches from 2007 to 2021. As the main feature of this review, we summarize the synthetic pathways for the isoindolinones, highlighting the synthetic precursors, which include different ortho-substituted aromatic substrates via multistep or tandem protocols, under metal-free conditions. We also discuss the mechanistic pathway of each methodology for the formation of isoindolinones. [ABSTRACT FROM AUTHOR]

The analysis of the multimode behavior of the interaction cavity for 42-GHz gyrotron is presented here. The in-house developed codes single-mode cold cavity solver (SMCCS) and GYCAD and commercial particle-in-cell (PIC) simulator MAGIC are used in the design and analysis of 42-GHz gyrotron cavity. SMCCS is used for the calculation of cold cavity parameters such as $Q$ factor, resonant frequency, and the axial electric field profile, which are further used in the beam–wave interaction computation. The PIC code is used here for the parametric optimization and time-dependent-multimode beam–wave interaction simulations of the interaction cavity. The mode purity in terms of the electromagnetic power in individual modes is also calculated using the data generated in the beam–wave interaction simulations. The single-mode analysis of the cavity is also performed using the analytical code GYCAD based on the generalized nonlinear theory. The results obtained by the PIC simulator and GYCAD are discussed and compared here. The analysis of the electron beam misalignment, which may occur due to the radial shifting or tilting of the different components during the fabrication of the device, is also performed and the effects on the efficiency, mode competition, and mode stability are discussed in detail. [ABSTRACT FROM AUTHOR]

The authors would like to make a correction to the affiliation section of on page 1, because one of the affiliations in was missing. The correct affiliation section of should read as follows. [ABSTRACT FROM AUTHOR]

In this work, a graphene-dielectric multilayer hyperbolic metamaterial (GHMM) has been analyzed for the generation of THz Cherenkov radiation (CR) from graphene surface plasmonics (GSP), induced by a moving electron bunch. The structure under analysis consists of a graphene-dielectric multilayer HMM in which the top graphene layer is considered as an interface between air and the underlying multilayer as the substrate. The dispersion analysis of the structure shows the existence of bulk-HMM (BH) and non-bulk HMM (NBH)-region in the ω – k space. The structure is found to generate intense CR from the GSP, when the operating point of the electron bunch lies in the BH-region, as the bulk states of the HMM substrate allows the efficient transformation of high-k GSP into THz-CR. The proposed structure can be exploited as a potential candidate for the development of low-voltage, electron beam-driven, ultra-tunable, compact graphene plasmonic Cherenkov THz radiation source. Moreover, the application of the principle of utilizing bulk states of HMM for CR generation has also been discussed for black phosphorous (BP), an emerging 2Dmaterial for the THz to infrared (IR) region. [ABSTRACT FROM AUTHOR]

This article presents the effect of significant up-tapering of the resonator midsection on diffractive quality factor, resonant frequency, axial field profile shift, and axial separation between peaks of higher order axial modes (HOAMs) in a gyrotron resonator. Significant up-tapering of the resonator midsection causes the quality factor curves of HOAMs to come close to each other and eventually crossover. This allows HOAMs to have comparable or even higher quality factor value than the lower axial modes—a situation which is not possible in a conventional resonator. Due to this, the operating current for all axial modes can keep an order of magnitude. The up-tapering also shifts the axial field profile toward the output section of the resonator and leads to the loss of spatial symmetry that exists in the axial separation between the peaks of HOAMs in a conventional resonator. Computations have been performed for 0.2-, 0.5-, and 1-THz resonator using single-mode cold cavity solver code developed at CSIR-CEERI. Numerical validation with published results, for 0.2- and 0.5-THz conventional resonators, has also been carried out. [ABSTRACT FROM AUTHOR]

The 42-GHz gyrotron cavity had three sections in its final design: down-taper section, up-taper section, and uniform middle section. The design of the cavity depends on the RF mode and desired power growth. The finalized design parameters of down-taper and up-taper angles are 2° and 3°, respectively, with respect to the middle section of gyrotron cavity. This cavity consists of these poorly tapered sections at both the ends of midsection. The combination of all three sections results into a complex cavity structure which is complicated and challenging to fabricate. An additional challenge in fabrication is to achieve desired designed parameters. Therefore, design realization through fabrication clearly needs dimensional measurement. The dimensional parameters of cavities such as down-and up-taper angles, uniform section diameter, taper lengths, and surface roughness measurement have their own significance and importance. This paper presents the destructive and the nondestructive methods to measure the dimensional parameters of a complex cavity structure. Further, a computational analysis is also done to represent the comparisons between the design and measured values in terms of ohmic quality factor and efficiency and reported the effects of geometrical changes. [ABSTRACT FROM AUTHOR]

Heterocyclic molecules exhibit significant importance as they possess pharmacological, biological, and industrial applications. Although several excellent synthetic routes have been established for heterocyclic molecules, sustainable synthetic procedures such as microwave, ultrasound, grinding, photochemical, and thermodynamic route maps are needed to be explored further. Furthermore, these techniques become more eco-compatible when they produce value-added products in the absence of solvent. The advantages of these methodologies are to generate a library of small molecules, which will eventually combine to form complex bioactive molecules. In this review, we have emphasized recent studies (2010 to 2022) on the solvent-free conditions of various heterocycles (N, O, S), which have been synthesized via oxidation, reduction, condensation, and conjugated reactions. In this literature survey, glimpses of methodologies with their advantages, mechanistic considerations, and limitations are highlighted. These sustainable, and economically feasible routes will pave the way for a revolutionary corridor in the near future. [ABSTRACT FROM AUTHOR]

Magnetron injection gun (MIG) is an important and critical part of any gyrotron. The overall performance of gyrotron deeply depends on the quality of gyrating electron beam. In this article, the design of triode type magnetron injection gun for 200 GHz frequency tunable gyrotron is discussed. It is planned to design and develop a 200 GHz gyrotron for 300 MHz DNP-NMR spectroscopy. The triode MIG is designed in such a way that it can be used in 200 GHz gyrotron of higher RF power for other applications also such as electron spin resonance, imaging. First, geometrical and electrical parameters of MIG are calculated using trade-off and scaling equations. Based on the calculated parameters, further, electron beam trajectory simulations are performed in EGUN. The geometry of electrodes are optimized through numerous simulation iterations to achieve the required beam parameters, such as, minimum spread in velocity and guiding center radius, an optimum value of velocity ratio (1.3–1.5), guiding center radius as per the maximum beam-wave coupling strength. The magnet system is designed to achieve the smooth Gaussian type of magnetic field profile with peak value of 7.35 T at cavity center. Further detail parametric analyses are performed which would be helpful in the frequency tuning and long-time stable operation of gyrotron device. [ABSTRACT FROM PUBLISHER]

In this paper, we present the RF behavior of conventional cylindrical interaction cavity for 240 GHz, 1 MW gyrotron for futuristic plasma fusion reactors. Very high-order TE mode is searched for this gyrotron to minimize the Ohmic wall loading at the interaction cavity. The mode selection process is carried out rigorously to analyze the mode competition and design feasibility. The cold cavity analysis and beam-wave interaction computation are carried out to finalize the cavity design. The detail parametric analyses for interaction cavity are performed in terms of mode stability, interaction efficiency and frequency. In addition, the design of triode type magnetron injection gun is also discussed. The electron beam parameters such as velocity ratio and velocity spread are optimized as per the requirement at interaction cavity. The design studies presented here confirm the realization of CW, 1 MW power at 240 GHz frequency at TE mode. [ABSTRACT FROM AUTHOR]

A review on the sub-THz/THz gyrotrons is performed in this manuscript. The present development status of gyrotrons can be divided into three streams for the sake of better understanding: 1. low frequency (<35 GHz), medium power (<100 kW), small size and easy to handle gyrotrons for industrial applications, 2. very high power (1 MW or more), medium frequency (100–200 GHz) gyrotrons for plasma fusion applications, 3. low power (few tens of watt to kW), high frequency (>200 GHz) gyrotrons for various innovative applications. In this manuscript, the third stream of gyrotron development is reviewed. In last few decades several innovative applications are searched in sub-THz/THz band where the gyrotrons could be used as an efficient source of RF radiation. The applications of sub-THz/THz gyrotrons including the futuristic scope of the device are also discussed in this article. Further, several criticalities arise in the design and development when the gyrotron operation shifts toward the high frequency band. Various such design and technological challenges are also discussed here. Finally the development status of sub-THz/THz gyrotrons as per the use in various scientific and technological applications is also discussed. [ABSTRACT FROM AUTHOR]

Correction to: Appl Phys A (2020) 126:882 https://doi.org/10.1007/s00339-020-04064-6 In this article, the affiliation 2 for Nalini Pareek and Anirban Bera was incorrectly given. Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. [Extracted from the article]

Microorganisms present in the guts are the causative agents for various diseases in humans. More and more studies are correlating such diseases and the responsible microorganism. The Gram-positive bacterium Ruminococcus gnavus (R. gnavus) has been identified to be responsible for symptoms of Crohn's disease. R. gnavas produces a glucorhamnan polysaccharide and it is postulated that this polysaccharide induces inflammatory response through toll-like receptor 4 (TLR4). The current manuscript describes the chemical synthesis of the pentasaccharide repeating unit of the O -polysachharide from R. gnavus. The major challenge associated with this particular synthesis is the presence of two consecutive 1,2- cis glucose units. The target oligosaccharide is achieved through a linear strategy from commercially available sugars through rational protecting group manipulation. 1,2- cis glycosylation of glucose through remote participation of acyl group at the 6- O position is used successfully with excellent yield. In both cases, sole 1,2- cis products are obtained at −20 °C through the activation of thioglycosides. [Display omitted] • Total synthesis of the pentasaccharide repeating unit of Ruminococcus gnavus. • Potential vaccine design. • Stereoselective 1,2- cis glucosylation. • Remote participation of 6- O -acyl group. [ABSTRACT FROM AUTHOR]

Correction for 'Recent developments in the solvent-free synthesis of heterocycles' by Nilabrata Dey et al., New J. Chem., 2023, https://doi.org/10.1039/d3nj01991h. [ABSTRACT FROM AUTHOR]

Inverse magnetron injection gun (IMIG) provides several advantages over simple MIG especially in high-power, high-frequency gyrotron. Sub-millimeter (>230 GHz), high-power (≥1 MW) gyrotrons would be required in futuristic plasma fusion machines to fulfill the need of tens of megawatt RF power for electron cyclotron resonance heating. Here, in this paper, an IMIG is designed for 0.24-THz, 1-MW gyrotron. First, the tradeoff design equations and technical constraints are used to synthesize the electrodes geometry and electrical parameters of IMIG. This synthesized IMIG model is further simulated to finalize the design using electron trajectory code EGUN. Simultaneously, the magnet system including the auxiliary gun coils and superconducting magnets (SCM) is also designed and the obtained magnetic field profile is used in the IMIG simulations. In the case of high-power MIG, the suppression of the beam halo is a major design concern and analyzed critically in the present IMIG design. The shape of the modulating anode and main anode is optimized to make a beam halo shielding. This IMIG is designed for a very high-order mode (TE46,17) simple cylindrical cavity, which confines the range of the tolerance in the electron beam parameters. So, a detailed parametric and misalignment analysis is also performed with respect to the electron beam parameters, such as pitch factor, velocity spread, and guiding center radius spread. These parametric and misalignment analyses would be utter helpful in the fabrication, assembling and testing of the IMIG as well as gyrotron. [ABSTRACT FROM AUTHOR]

A klystron is an important vacuum device which is useful in medical linear accelerators because it amplifies the radio-frequency (RF) signals required to produce high-energy particle beams. The properties of the nonlinear input and output dynamics in the klystron circuit arouse distortion in various types of parameters pertaining to the beam voltage, beam current, RF power, and operating frequency from unpredictable external factors. Therefore, low-level RF (LLRF) control systems can facilitate the regulation of the output of the klystron to a desired level. Low-level RF control system of the klystron is designed to stabilize the applied voltage and control the resonance frequency of the cavity of the klystron. In this work, an infallible low-level RF control system, the most suitable for a klystron, is designed to use a beam monitoring and an interlock system with components that include an isolator and a phase shifter. Moreover, with regard to pulse distortion at the flap top at the RF output power, the stability of the RF power pulse at the flap top part was improved somewhat by a variable inductor which controlled the inside of the pulse modulator. In this LLRF control experiment, the pulse modulator generated 140kV-95A and succeeded in generating RF output power of 2.856GHz-6MW level of an S-band klystron. During this process, the efficiency of the RF power was approximately 42∼45% and the pulse repetition rate was 10 Hz. The flattop pulse width was measured and found to be 1 µs. [ABSTRACT FROM AUTHOR]

An efficient substrate dependent NaN3/NH4Cl promoted aza‐cyclization was developed via metal free cascade transformation. A wide variety of bicyclic/tricyclic isoindolinone derivative was achieved with excellent diastereoselectivity from achiral reagent system. This protocol also provided synthetic route of dopamine D4 receptor in short way. The bio‐imaging study towards CHO cell line with our isoindolinone embedded new fluorophore was also demonstrated. An efficient substrate dependent NaN3/NH4Cl promoted aza‐cyclization was developed via metal free cascade transformation. A wide variety of bicyclic/tricyclic isoindolinone derivative was achieved with excellent diastereoselectivity from achiral reagent system. This protocol also provided synthetic route of dopamine D4 receptor in short way. The bio‐imaging study towards CHO cell line with our isoindolinone embedded new fluorophore was also demonstrated. [ABSTRACT FROM AUTHOR]

Multimegawatt RF power in millimeter waveband (30–300 GHz) is required in the magnetically confined plasma fusion reactors. In this paper, the design of 170-GHz, 2-MW gyrotron with coaxial-cavity configuration is discussed. The mode selection and optimization of corrugation geometry of the coaxial insert are performed and discussed in detail. The beam-wave interaction computation and interaction cavity design are carried out using a particle-in-cell code. The beam-wave interaction analysis confirms 2.2-MW RF power at the 170.07-GHz frequency with more than 40% interaction efficiency. A 5.5-MW coaxial magnetron injection gun (C-MIG) is designed to launch the gyrating electron beam at the first radial maxima of the electric field peak of the selected operating mode in the interaction cavity. The magnetic system consisting of auxiliary coils and superconducting coils is also designed as per the requirement in MIG design. [ABSTRACT FROM AUTHOR]

In this paper, the design and development of magnetron injection gun (MIG) for 170 GHz, 1-MW gyrotron have been presented. The triode-type MIG at 80-kV beam voltage and 40-A beam current has been designed and developed. A gun-collector test module for 170-GHz gyrotron has been developed and vacuum processed at 400 °C with continuous 48 h operation. The cathode activation and high-voltage breakdown testing have also been carried out up to desired rating. The simulation result of MIG by EGUN has been validated with 2-D-code TRAK. [ABSTRACT FROM AUTHOR]

Abstract: A high‐quality‐factor (high‐Q) metallic Fano metamaterial is demonstrated both experimentally and theoretically. This material is suitable for highly efficient Cerenkov lasing in which subwavelength metallic slits are arranged to form asymmetric unit cells. In contrast to conventional dielectric Cerenkov or Smith–Purcell devices, in the proposed device, convection electrons traverse the high‐Q metallic metamaterial. The interplay between an extremely low group velocity from the infinite transverse permittivity of the anisotropic metamaterial and the subradiant damping from a Fano‐type slit mode is shown to be responsible for the high‐Q value, which is measured to be unprecedented at 700. The resulting improvement in the Cerenkov lasing efficiency is estimated to be more than two orders of magnitude using a particle‐in‐cell simulation. [ABSTRACT FROM AUTHOR]

An analysis of the effects of electromagnetic pulses from a high-power microwave (HPM) radiation technique is conducted using a relativistic backward-wave oscillator (RBWO) which uses relativistic electron beams in vacuum circuits. The application described here is based on a relativistic electron device and uses relativistic electron beams to generate high-power electromagnetic radiation. The RBWO was fabricated to operate in a relativistic region with a gamma factor (γ) of 2 at an acceleration voltage of 500 kV. A mode-converted relativistic back-wave oscillator with an antenna that converts TM01to TE11was designed and fabricated because the electric field of the center in the RBWO circuit is null. The effects on electronic devices by HPM radiation and exposure were assessed. The effects on electronic devices exposed to HPMs, the failure of information equipment, and modulation of and interference with the received signal through a theoretical model of the threshold power relative to the influence on the target were confirmed in a high-output microwave exposure environment. Particularly, information devices containing semiconductors can undergo serious failures and breakdowns due to the thermal secondary breakdown caused by the high-output transient electromagnetic waves, and it is a theoretical consideration that reverse voltage occurs due to the generation of surge current when caught in the PN-junction region. Finally, the range of power regarding the effectiveness of the electromagnetic coupling of electronics exposed to HPM radiation was estimated. [ABSTRACT FROM PUBLISHER]

Researchers have investigated plasma-related phenomena and internal breakdowns in the gigawatt–terahertz relativistic backward wave oscillator (RBWO) caused by field emissions from the surfaces of the waveguide circuits in these oscillators. In order to increase the power-handling capability of relativistic electron beam devices, an RBWO is proposed in the form of an oversized structure in which the diameter ( $D$ ) of the electrodynamic structure is increased to several times the free-space wavelength ( $\lambda )$ . An optimal periodic rectangular corrugation structure of which the axial mode is matched to the $\pi $ mode is designed in order to determine only the TM01 mode without mode competition in a slow-wave structure (SWS). The oversized RBWO has a fairly large diameter and uses a resonant reflector to achieve optimum efficiency while also preventing mode competition in the SWS. Absorption of a decelerated electron beam is achieved by the collector, which protects against breakdown and damage. The results of 0.5–0.1 THz from 500 kV–5 kA in the relativistic region are observed by means of a particle-in-cell simulation, and the dispersion relationship is determined by a finite-difference time-domain simulation. The outcomes show that a high-power oversized RBWO can control the selection of the mode and the interaction efficiency. [ABSTRACT FROM PUBLISHER]

Highlights: [•] The complete electrical design of 42GHz, 200kW gyrotron is presented. [•] Un-depressed collector and axial output system for RF power is selected. [•] Various commercially available design tools as well as in-house developed computer codes are used in the design process. [•] The experimental results of cold cavity analysis are also presented. [•] The design results show more than 200kW power with 40% interaction efficiency at 42GHz frequency. [Copyright &y& Elsevier]

When a semiconductor element is irradiated with radiation in the form of a transient pulse emitted from a nuclear explosion, a large amount of charge is generated in a short time in the device. A photocurrent amplified in a certain direction by these types of charges cause the device to break down and malfunction or in extreme cases causes them to burn out. In this study, a pulse-type γ-ray generator based on a relativistic electron beam accelerator (γ=2.2, β=0.89) which functions by means of tungsten impingement was constructed and tested in an effort to investigate the process and effects of the photocurrent formed by electron hole pairs (EHP) generated in a pMOSFET device when a transient radiation pulse is incident in the device. The pulse-type γ-ray irradiating device used here to generate the electron beam current in a short time was devised to allow an increase in the irradiation dose. A precise signal processing circuit was constructed to measure the photocurrent of the small signal generated by the pMOSFET due to the electron beam accelerator pulse signal from the large noise stemming from the electromagnetic field around the relativistic electron beam accelerator. The pulse-type γ-ray generator was installed to meet the requirements of relativistic electron beam accelerators, and beam irradiation was conducted after a beam commissioning step. [ABSTRACT FROM AUTHOR]