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A miniature planar meander-type slow-wave structure (SWS) for a W-band traveling-wave tube is studied. Computer simulation of the SWS electrodynamic parameters is performed. A new technology for fabrication of planar microstrip SWSs with the aid of laser ablation is proposed. The S-parameters of the SWS are experimentally studied. The experimental data are in good agreement with the results of the 3D computer simulation. Output characteristics of the traveling-wave tube with a sheet electron beam and planar SWS are calculated.

Sources of millimeter and submillimeter (terahertz) band radiation are very important in modern society due to their broad application from telecommunication to non-destructive evaluation and chemical analysis. In this work, we present a review of technological approaches for fabrication of RF structures of µVEDs. Technological approaches to the microfabrication of planar slow-wave structures (SWS) on dielectric substrates operating with a sheet electron beam are considered. Such SWSs are attractive due to the simplicity of the structure, compact dimensions, low voltage operating, and wide bandwidth. We consider lithography-based technology, deep reactive ion etching, computer-numerical-control (CNC) micro- and nano-milling, electrical discharge micromachining, and technologies based on the additive manufacturing such as three-dimensional (3-D) printing, selective laser sintering, and selective laser melting. We also describe an original approach to microfabrication of planar structures based on magnetron sputtering and CNC laser ablation. Fabrication tolerance and surface roughness provided by the considered technologies are compared.

For miniaturized vacuum-tube electron devices at millimeter and submillimeter (THz) bands, the possibility of low-voltage operation is of primary importance. Planar slow-wave structures (SWS) on dielectric substrates are favorable for the low-voltage operation. In this paper, we discuss design, fabrication and cold test of millimeter-wave planar SWSs. We consider the microstrip meander-line SWSs, which are designed for operation in traveling-wave tube power amplifiers with sheet electron beam.

Slow-wave structure (SWS) is a core part of a traveling-wave-tube (TWT) amplifier. In this letter, the planar microstrip meander SWS on a dielectric substrate at $V$ -band (50–70 GHz) is studied. The basic electromagnetic parameters of the SWS are calculated. The SWS circuits are designed and fabricated, and good transmission characteristics are measured. The SWS developed is characterized by a wide bandwidth and a relatively-large slow-wave factor, and is suitable for a low-voltage TWT with the sheet electron beam.

We consider further development of our original technology for microfabrication of millimeter-band planar microstrip slow-wave structures (SWS). The technology is based on magnetron sputtering and laser ablation methods. V-band (50-75 GHz) and W-band (75-110 GHz) SWSs are fabricated and characterized by scanning electron and optical microscopy. Electromagnetic parameters of the developed SWSs are studied by numerical simulation and cold-test measurement. We have also carried out preparations and preliminary technological steps for the microfabrication of D-band (110-170 GHz) planar microstrip slow-wave structures.

A traveling wave tube amplifier (TWTa) operating in V-band (62–65 GHz) was designed considering a planar slow wave structure (SWS). Particle in cell simulations were performed to calculate the gain and the output power of the TWT. The simulated TWT showed a maximum gain of 36 dB at 64 GHz and an output power of 16 W. The planar SWS was then fabricated with a laser machining technique. S parameters measurements of the SWS showed excellent matching and low losses in the operating frequency band.

Here we report on experimental and numerical investigations of an electrodynamic structure assembled according to photonic crystals' principles placed inside a X-band rectangular waveguide which is promising for microwave electronics. The features of dispersion characteristics of photonic crystals can be used for efficient excitation of high-order (and, hence, high-frequency) electromagnetic modes. In this work, the electrodynamic structure is a2D array of thin metal pins. Transmission and reflection of proposed system were measured experimentally and evaluated numerically. The experimental results are in good agreement with the numerical ones.

The elaboration of biocompatible and biodegradable carriers for photosensitizer targeted delivery is one of the most promising approaches in a modern photodynamic therapy (PDT). This approach is aimed at reducing sides effects connected with incidental toxicity in healthy tissue whilst also enhancing drug accumulation in the tumour area. In the present work, Photosens-loaded calcium carbonate (CaCO3) submicron particles in vaterite modification are proposed as a novel platform for anticancer PDT. Fast penetration of the carriers (0.9±0.2μm in diameter) containing 0.12% (w/w) of the photosensitizer into NIH3T3/EGFP cells is demonstrated. The captured particles provide the dye localization inside the cell increasing its local concentration, compared with "free" Photosens solution which is uniformly distributed throughout the cell. The effect of photosensitizer encapsulation into vaterite submicron particles on cell viability under laser irradiation (670nm, 19mW/cm(2), 10min) is discussed in the work. As determined by a viability assay, the encapsulation renders Photosens more phototoxic. By this means, CaCO3 carriers allow improvement of the photosensitizer effectiveness supposing, therefore, the reduction of therapeutic dose. Summation of these effects with the simplicity, upscalability and cheapness of fabrication, biocompatibility and high payload ability of the vaterite particles hold out the prospect of a novel PDT platform.

We report the results of the design, simulation, fabrication, and cold-test measurements of millimeter-band 2D planar microstrip slow-wave structures (SWSs) on dielectric substrates. Such structures have a high slow-wave factor, which allows for low-voltage operation and reduction in the size and weight of the device. A low-cost and flexible fabrication technology based on magnetron sputtering and subsequent laser ablation has been developed and is reported in the paper. Microstrip meander-line SWS circuits at V-, W-, and D-bands have been fabricated and characterized. The fabrication of ring-bar planar SWSs by the photolithographic method is also discussed. Experimental measurement of S-parameters of the fabricated structures reveals good transmission properties. Return loss (S11) does not exceed −10 dB and attenuation is about 2 dB/cm in the V-band, 10 dB/cm in the W-band, and 8.5 dB/cm in the D-band.

A novel technology for microfabrication of millimeter-band planar microstrip slow-wave structures is considered. The technology is based on magnetron sputtering and laser ablation methods. The magnetron sputtering method is used to deposit a thin layer of metal (copper) on a dielectric substrate. Then laser ablation is utilized to cut a slow wave structure from the copper layer. V-band (50–70 GHz) and W-band (75–110 GHz) meander-line slow wave structures are fabricated and characterized by scanning electron and optical microscopy. Electromagnetic parameters of the developed slow wave structures are studied by numerical simulation. Cold-test measurement are also carried out for microfabricated meander-line slow wave structures. The experimental results are in good agreement with the numerical ones. The proposed technology has significant advantages in cost, speed and flexibility over lithography processes commonly utilized for such applications. The future work will be aimed to expansion of the proposed technology to manufacturing of higher-frequency E-band (110–170 GHz) planar slow wave structures.

Folded waveguide (FW) is a promising type of slow-wave structure (SWS) for millimeter-wave traveling-wave tubes. Results of development of several millimeter-band FW SWSs are presented. SWS circuits at Q- and V -band are fabricated by CNC-machining. Cold electromagnetic parameters of the SWS characteristics are simulated and reasonable agreement with the results of measurements is observed. Small-signal and large-signal gain is calculated.

A novel technology for microfabrication of millimeter-band planar microstrip slow-wave structures (SWS) is proposed. The technology is based on magnetron sputtering and laser ablation methods. V-band (50–70 GHz) and W-band (75–110 GHz) meander-line SWSs are fabricated and characterized by scanning electron and optical microscopy. Electromagnetic parameters of the developed SWSs are studied by numerical simulation and cold-test measurement. Small-signal and large-signal gain is calculated.

Microfabricated vacuum-tube millimeter- and THz-band sources are of great interest for numerous applications such as communications, radar, sensors, imaging, etc. Recently, miniaturized sheet-beam traveling-wave tubes for operation at sub-THz and THz bands have attracted a considerable interest. In this paper, we present the results of modeling and development of slow-wave structures (SWS) for medium power (10-100 W) traveling-wave tubes (TWT) amplifiers in near-THz frequency band. Different types of SWSs are considered, such as double-vane SWS for TWT with a sheet electron beam, folded-waveguide SWS, and novel planar SWSs on dielectric substrates.

A novel technology for microfabrication of millimeter and THz band planar microstrip slow-wave structures (SWS) is proposed. The technology is based on magnetron sputtering and laser ablation methods. The magnetron sputtering method is used to deposit a thin layer of metal (copper) on a quartz substrate. Then laser ablation is utilized to fabricate a slow wave structure from the copper layer. V-band (50–70 GHz) meander-line SWSs were fabricated and characterized by scanning electron and optical microscopy. The proposed technology has significant advantages in cost, speed and flexibility over lithography processes commonly utilized for such applications. The future work will be aimed to expansion of the proposed technology to manufacturing of higher-frequency W-band (75–110 GHz) and E-band (110–170 GHz) planar SWSs.

In this work we report the results of numerical simulation and cold-test measurements of electromagnetic parameters of the V-band (50–70 GHz) meander-line slow wave structure. The microstrip meander-line slow wave structure is suitable for using in a millimeter-band traveling wave tube amplifiers. Several samples of copper microstrip meander-line slow wave structure on a quartz substrate consisting of 50 meander periods with input and output couplers were designed and fabricated. The slow wave structure was microfabricated by using our original and novel technology for microfabrication. The technology is based on magnetron sputtering and laser ablation methods. The magnetron sputtering method is used to deposit a thin layer of metal (copper) on a quartz substrate. Then laser ablation is utilized to cut a slow wave structure from the copper layer. This technique is a more facile, flexible and lower cost as compared to photolithography method. Transmission and reflection of microfabricated SWS were measured experimentally and calculated numerically. The results of the experimental cold-test measurements are verified by numerical simulations. Electromagnetic parameters of the slow wave structures were simulated using the finite-element ANSYS HFSS and COMSOL Multiphysics software packages. The results obtained with these two codes are in excellent agreement with each other and good agreement between experimental and numerical results is also observed.

A novel type of microcontainers based on hollow silver alginate microspheres and magnetite nanoparticles is reported as development of recently published technology. Magnetite nanoparticles were incorporated by two methods - co-precipitation with porous calcium carbonate during template formation and adsorption onto CaCO3 particles or microcontainers' shell. Amount of magnetite loaded and microshells size (4.6 to 6.9 μm) were found to depend on the chosen method for magnetite nanoparticles incorporation. Stability of hollow microshells in saline, phosphate buffer and culturing media was studied. Microcontainers' susceptibility to magnetic field was investigated in solutions of varied viscosity, and their group movement velocity under constant magnetic field was evaluated by sequential optical microscopy imaging. Cell viability tests with prepared microshells were performed that demonstrated negligible cytotoxicity effect on human dermal fibroblasts cells. With HeLa cells moderate viability inhibition was found at high carriers:cells ratio at early time points which is attributed to more active and receptor-mediated endocytosis of carriers as well as known cytotoxicity of magnetite in some cancer cells. At 24 and 48 h time points HeLa cells proliferation fully recovers. Reported data opens perspectives for further biomedical-oriented studies and application of this novel kind of microcontainers with a number of techniques applicable for imaging, control and triggered cargo release provided by presence of silver and magnetite nanoparticles in the carriers and their suitability for further versatile functionalization by traditional LbL approach if needed.

We have proposed a method to form electron bunches in multivelocity electron beams that provide an increase in amplitudes of higher harmonics in the spectrum of output radiation of low-voltage vircator system. The low-voltage vircator system employs additional spread of electron velocities caused by the control electrode and makes it pos possible to choose the voltage providing the formation of the translaminar layer of electrons and additionally decelerate the electron beam by the static collector field. The numerically simulated results are in qualitative agreement with the experimental data.

Properties of microfabricated V-band (50-70 GHz) meander slow-wave structures (SWS) for low- voltage tubes with sheet electron beam are studied by numerical simulation and cold-test measurement. The SWS was microfabricated by using magnetron sputtering and laser ablation processes. Transmission and reflection of proposed SWS were measured experimentally and calculated numerically. The experimental results are in good agreement with the numerical ones.

A novel technology for microfabrication of millimeter-band planar microstrip slow-wave structures (SWS) is proposed. The technology is based on magnetron sputtering and laser ablation methods. The magnetron sputtering method is used to deposit a thin layer of metal (copper) on a quartz substrate. Then laser ablation is utilized to cut a slow wave structure from the copper layer. V-band (50-70 GHz) meander-line SWSs were fabricated and characterized by scanning electron and optical microscopy. The proposed technology has significant advantages in cost, speed and flexibility over lithography processes commonly utilized for such applications.