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The cell-type continuous electromagnetic radiation system is a demonstration device capable of generating high-power millimeter electromagnetic waves of a specific wavelength and observing their effects on living organisms. It irradiates a biological sample placed in a 30 × 30 × 50 cm3 cell with electromagnetic waves in the 3.15-mm-wavelength region (with an output of ≥1 W) and analyzes the temperature change of the sample. A vacuum electronic device-based coupled-cavity backward-wave oscillator converts the electron energy of the electron beam into radiofrequency (RF) energy and radiates it to the target through an antenna, increasing the temperature through the absorption of RF energy in the skin. The system causes pain and ultimately reduces combat power. A cell-type continuous electromagnetic radiation system consisting of four parts—an electromagnetic-wave generator, a high-voltage power supply, a test cell, and a system controller—generates an RF signal of ≥1 W in a continuous waveform at a 95-GHz center frequency, as well as a chemical solution with a dielectric constant similar to that of the skin of a living organism. An increase of 5 °C lasting approximately 10 s was confirmed through an experiment.

Boron–neutron capture therapy (BNCT) is a cancer treatment method that exploits the high neutron reactivity of boron. Monitoring the prompt gamma rays (PGs) produced during neutron irradiation is essential for ensuring the accuracy and safety of BNCT. We investigate the imaging of PGs produced by the boron–neutron capture reaction through Monte Carlo simulations of a gamma camera with a SrI2 scintillator and parallel-hole collimator. GAGG scintillator is also used for a comparison. The simulations allow the shapes of the energy spectra, which exhibit a peak at 478 keV, to be determined along with the PG images from a boron–water phantom. It is found that increasing the size of the water phantom results in a greater number of image counts and lower contrast. Additionally, a higher septal penetration ratio results in poorer image quality, and a SrI2 scintillator results in higher image contrast. Thus, we can simulate the BNCT process and obtain an energy spectrum with a reasonable shape, as well as suitable PG images. Both GAGG and SrI2 crystals are suitable for PG imaging during BNCT. However, for higher imaging quality, SrI2 and a collimator with a lower septal penetration ratio should be utilized.

High-power microwave sources applied to a directed-energy weapon can lead to permanent damage by radiating concentrated energy in a specific direction to disturb or overload electronic equipment. The effect analysis on the target, such as electronics exposed to electromagnetic pulse, should be considered as an important factor in determining the performance of high-power microwave sources and conducting experimental evaluations. In this study, a magnetically insulated transmission line oscillator, one of the representative high-power microwave sources based on vacuum electronics device, was constructed and experimental analysis with respect to electromagnetic pulse effects was performed. The specification of the magnetically insulated transmission line oscillator used in this study corresponded to 3 GW of high-power electromagnetic wave pulses operating at L-band. The power efficiency was approximately 10 – 15%. For effective targeting, a Vlasov antenna that converts TM01 mode to TE11 mode was designed and fabricated. The radiation pattern was confirmed via fluorescent lamps, and to confirm the effect of the directed-energy weapon on the target, an effect analysis was performed using a portable electronic device as a sample. Furthermore, the electric field was measured with a D-dot probe and quantified and compared. This study presents a future blueprint of the value of the directed-energy weapon by predicting the radiant output power of the weapon in the far-field region after it is mounted on a movable ground vehicle or unmanned aerial vehicle.

To build a proton beam accelerator that can be applied to a boron neutron capture therapy system based on an electrostatic accelerator, a high-voltage direct-current (DC) power supply system equivalent to the generation of neutrons should be provided. The symmetrical Cockcroft-Walton voltage multiplier method is suitable for stable acceleration of the proton beam in the tandem electrostatic accelerator in this system. Before the second step-up with the Cockcroft-Walton circuit, the design of the inverter is prioritized by preponderantly considering the first voltage and resonance frequency. Moreover, the optimized stacking number is determined with consideration of the ripple voltage, voltage drop, average output voltage, and fundamental harmonics, and a design is performed to set related parameter values to be stable in the flat-top region of the voltage. A high-voltage DC power supply system of 1.2 MV/45 mA is needed for a stable terminal energy of 2.4 MeV/20 mA. Such a design can be optimized by securing reliable data using a simulation tool on the basis of theoretical calculations. This will become a formidable touchstone in manufacturing technology based on acquiring practical know-how for setting up a tandem electrostatic accelerator-based boron neutron capture therapy system in the future.

Positronium (Ps) is an unstable system created by the temporary combination of electrons and negative electrons, and Ps generation technology under resonance conditions at millimeter waves is emerging as a new research topic. In general, Ps can be observed when an unstable separate state remains after electron and positron pair annihilation, as in positron emission tomography (PET). However, in this study, a plasma wakefield accelerator based on vacuum electronics devices (VEDs) was designed in the ponderomotive force generating electrons and positrons simultaneously using annular relativistic electron beams. It can induce Cherenkov radiation from beam–wave interaction by using dielectric materials. According to the size of dielectric materials, the frequency of oscillation is approximately 203 GHz at the range of millimeter waves. At this time, the output power is about 109 watts-levels. Meanwhile, modes of millimeter waves polarized by a three-stepped axicon lens are used to apply the photoconversion technology. Thus, it is possible to confirm light emission in the form of a light-converted Bessel beam.

The failure threshold time of semiconductors caused by the impact of irradiated high-power electromagnetic waves (HPEM) is experimentally studied. A SN7442 integrated circuit (IC) is placed in an emulator with a WR430 closed waveguide and is irradiated by HPEM generated from a magnetron oscillator. The state of the SN7442 component is observed by a light-emitting diode (LED) detector and the voltage measured in the SN7442 component. As the magnitude of the electric field in the HPEM is varied from 24 kV/m to 36 kV/m, the failure threshold time falls from 195 s to 17 s with dependence of the irradiated electric field (E) on the failure threshold time (T) from T~E−12 to a T~E−6.

Versatile high-power pulsed electron-beam accelerators that meet the requirements of pulsed high-power specifications are needed for appropriate applications in medical industry, defense, and other industries. The pulsed electron beam accelerator comprising a Marx generator and Blumlein pulse forming line (PFL) is designed to accelerate the electron beams at the level of 1 MeV when electrostatically discharging. The performance specifications of Marx generators consisting of a 100 kV DC power supply, R-L-C circuit, and high voltage switch are at a maximum 800 kV. At this time, by using the capacitance mismatching principle between the Marx generator and the Blumlein PFL under the law of preserving the amount of charge, it is possible to generate a high voltage in the form of a square pulse up to about 1.1 MV, as much as 1.37 times the charged voltage of the Marx generator. As a result, energy transmission from the Marx generator with a high efficiency of about 85% to the Blumlein PFL is possible. The aim of this study is that the pulsed high-power electron-beam accelerator can be used to change the diode impedance, and the energy of the accelerated electron beam reaches a level of 1 MeV with the square pulse width of about 100 ns at the flat-top in the range of relativistic electron beam generation. Performance tests were securely carried out by installing a dummy load based on CuSO4 solution varying the diode impedance to deter damage to the circuit by preventing reflected waves from being generated in the load.

Auricular cartilage reconstruction represents one of the greatest challenges for otolaryngology-head and neck surgery. The native structure and composition of the auricular cartilage can be achieved by combining a suitable chondrogenic cell source with an appropriate scaffold. In reconstructive surgery for cartilage tissue, autogenous cartilage is considered to be the best chondrogenic cell source. Polycaprolactone is mainly used as a tissue-engineered scaffold owing to its mechanical properties, miscibility with a large range of other polymers, and biodegradability. In this study, scaffolds with or without autogenous minced auricular cartilage were implanted bilaterally in rabbits for auricular regeneration. Six weeks (n = 4) and 16 weeks (n = 4) after implantation, real-time quantitative reverse transcription polymerase chain reaction and histology were used to assess the regeneration of the auricular cartilage. Quantitative reverse transcription polymerase chain reaction analysis revealed that the messenger RNA expression of aggrecan, collagen I, and collagen II was higher in scaffolds with 50% minced cartilage than the scaffold-only groups or scaffolds with 30% minced cartilage (P < 0.05). Furthermore, histological analysis demonstrated significantly superior cartilage regeneration in scaffolds with the minced cartilage group compared with the scaffold-only and control groups (P < 0.05). Autogenous cartilage can be easily obtained and loaded onto a scaffold to promote the presence of chondrogenic cells, allowing for an improvement of the reconstruction of auricular cartilage. Here, the regeneration of auricular cartilage was also successful in the 50% minced cartilage group. The results presented in this study could have clinical implications, as they demonstrate the potential of a 1-stage process for auricular reconstruction.

Ion thruster is the most efficient population system of satellite to control its orbits in deep space. Total efficiency, thrust, and specific impulse are the key characterization parameters of an ion thruster which define its performance. At present, total efficiency is limited within the range of 36–68%. In this paper, a new grid design is discussed to increase the total efficiency and thrust of ion thruster wherein screen grid has chamfered edges. The ion beam dynamics were simulated in OPERA14.0-3D. The simulated result is shown to have increased thrust and total efficiency from 0.196–0.364 mN and 41.29–74.66%, respectively.

The 3-D particle-in-cell (PIC) simulations are performed to determine the origin of sideband and spurious noises generated in a cooker magnetron. A novel simulation technique is used, which introduces cathode emission current nonuniformities. These nonuniformities are due to nonuniform distributions of electric field on a thermionic emission surface, which result from cathode geometry. It is shown that cathode end-caps shape and magnetic pole-piece geometries are the causes of sideband and spurious noises in conventional microwave ovens. The 3-D simulation results are in satisfactory agreement with the spectrum of a typical cooker magnetron.

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 ...

The field emission properties of the controlled emission edge of a vertically aligned graphene-based thin film are presented. A current and current density of above 7 mA and 200 A/cm2, respectively...

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.

By manipulating Fano resonance in metallic metamaterial, trapping and releasing of electromagnetic wave can be controlled. Simply, by varying the size of structural asymmetry to the proposed metallic slit structure, Q factor of trapped mode in metallic metamaterial can be tailored. We show that optimizing the electromagnetic property of Fano metamaterial can maximizes the interaction between convection electron and trapped mode, which gives significantly high efficiency of Cerenkov radiation larger than one from the ordinary Cerenkov and Smith-Purcell effects by order of two. We also observed inversion of the spectral asymmetry and the phase shift of high-Q trapped modes in subwavelength slits by manipulating the direction of the structural asymmetry of unit cell paving the way for full control of Fano resonances This finding is thought to be useful for many other potential applications other than Cerenkov lasing such as sensing and optical switching.

Generally, as the operating frequency of the electromagnetic wave increases, the maximum output becomes smaller and the wavelength of the wave becomes smaller, so that the size of the circuit cannot but be reduced. Particularly, fabrication of a circuit with a high-power terahertz (THz) wave frequency band of kW or more is limited due to the problem of circuit size on the order of μm to mm. In order to overcome these limitations, this paper proposes a source design technique of 0.1THz-0.3GW levels with a cylindrical shape with a diameter of about 2.4cm. Modeling and computational simulation were performed to optimize the design of high power electromagnetic sources based on the Cherenkov radiation generation technology using the principle of plasma wake-field acceleration with ponderomotive force and artificial dielectrics. An effective design guideline has been proposed to facilitate the fabrication of large-power terahertz wave vacuum devices of large diameter that are less restricted in circuit size through objective verification.

A versatile digital Low-Level Radio Frequency (LLRF) system has been designed for the various energy cyclotrons being developed by Korea Institute of Radiological and Medical Sciences (KIRAMS). In this study, the contents of LLRF of $\pmb{8\mathrm{MeV}\sim 30\mathrm{MeV}}$ cyclotron, which is a typical circular accelerator for neutron capture therapy, are discussed. Here we present blue print to construct an effective LLRF control system of the cyclotron.

Uniform, highly conductive, thin film field emitters are in immense need for future development of high power compact terahertz(THz) vacuum electronic devices(VED). Reduced graphene oxide(rGO) based free standing film as high current sheet beam cathode is fabricated by hydrothermal method. This hydrothermal method facilitates highly conductive, thin, compact film. We achieved to get few micrometers to sub-micrometer thick film which is much thinner than conventional vacuum filtered film resulting in higher field enhancement factor, current density, and current. This approach can successfully establish a fabrication method for uniform, thin high current field emitter for high power THz VEDs.

The Fano metamaterial provides a way of trapping and releasing electromagnetic waves in microwave and terahertz regime. We show that, by utilizing the electromagnetic properties, the efficiency of radiation power from the Cerenkov effect in our recently proposed metallic metamaterial is much larger than the one from the ordinary Cerenkov and Smith-Purcell effects. The optimization of the efficiency was numerically conducted by manipulating the quality(Q) factor of the trapped Cerenkov light. The proposed metamaterial is suitable for developing compact and highly efficient free electron lasers.

The automodulation processes in backward-wave oscillator with an inclined electron beam (the clinotron) operating at low-focusing magnetic fields have been studied. The automodulation behavior has been analyzed in the clinotron for different angles of the beam inclination. It has been shown that at low magnetic fields, the RF transverse electric field may cause significant changes in electron trajectories, and hence in the beam–wave interaction power that leads to the automodulation.

A multimode theory of the resonant backward-wave oscillator (BWO) with an electron beam inclined with respect to the surface of a periodic structure—a clinotron—is presented. It is shown that mode interaction provides phase velocity variation in the interaction space. The beam–wave interaction power increases at a favorable phase velocity profile along the interaction space, which manifests as power peaks in the clinotron zone. In contrast, when it is nonfavorable, there is power drop in the bandwidth. Developed multimode theory results are in satisfactory agreement with the theory of a BWO with reflections and with particle-in-cell simulations.

Non-thermal irreversible electroporation (NTIRE) to avoid thermal damage to cells during intense DC ns pulsed electric fields (nsPEFs) is a recent modality for medical applications. This mechanism, related to bioelectrical dynamics of the cell, is linked to the effect of a DC electric field and a threshold effect with an electrically stimulated membrane for the charge distribution in the cell. To create the NTIRE condition, the pulse width of the nsPEF should be shorter than the charging time constant of the membrane related to the cell radius, membrane capacitance, cytoplasm resistivity, and medium resistivity. It is necessary to design and fabricate a very intense nanosecond DC electric field pulser that is capable of producing voltages up to the level of 100 kV/cm with an artificial pulse width (∼ns) with controllable repetition rates. Many devices to generate intense DC nsPEF using various pulse-forming line technologies have been introduced thus far. However, the previous Blumlein pulse-generating devices are clearly inefficient due to the energy loss between the input voltage and the output voltage. An improved two-stage stacked Blumlein pulse-forming line can overcome this limitation and decrease the energy loss from a DC power supply. A metal oxide silicon field-effect transistor switch with a fast rise and fall time would enable a high repetition rate (max. 100 kHz) and good endurance against very high voltages (DC ∼ 30 kV). The load is designed to match the sample for exposure to cell suspensions consisting of a 200 Ω resistor matched with a Blumlein circuit and two electrodes without the characteristic RC time effect of the circuit (capacitance =0.174 pF).

Hurst’s memory that roots in early work of the British hydrologist H.E. Hurst remains an open problem in stochastic hydrology. Today, the Hurst analysis is widely used for the hydrological studies for the memory and characteristics of time series and many methodologies have been developed for the analysis. So, there are many different techniques for the estimation of the Hurst exponent (H). However, the techniques can produce different characteristics for the persistence of a time series each other. This study uses several techniques such as adjusted range, rescaled range (RR) analysis, modified rescaled range (MRR) analysis, 1/f power spectral density analysis, Maximum Likelihood Estimation (MLE), detrended fluctuations analysis (DFA), and aggregated variance time (AVT) method for the Hurst exponent estimation. The generated time series from chaos and stochastic systems are analyzed for the comparative study of the techniques. Then, this study discusses the advantages and disadvantages of the techniques and also the limitations of them. We found that DFA is the most appropriate technique for the Hurst exponent estimation for both the short term memory and long term memory. We analyze the SOI (Southern Oscillations Index) and 6 tree-ring series for USA sites by means of DFA and the BDS statistic is used for nonlinearity test of the series. From the results, we found that SOI series is nonlinear time series which has a long term memory of H = 0.92. Contrary to earlier work, all the tree ring series are not random from our analysis. A certain tree ring series show a long term memory of H = 0.97 and nonlinear property. Therefore, we can say that the SOI series has the properties of long memory and nonlinearity and tree ring series could also show long memory and non-linearity.

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.

High power terahertz vacuum electron devices demand high current density and uniform emission dispenser cathode. It was found that the coating of noble metals e.g., Os, Ir, and Re on the surface of tungsten dispenser cathodes enhances the emission capabilities and uniformity. Hence metal coated cathode might be the best candidate for terahertz devices applications. In this study, ternary-alloy-film cathode (2Os:2Re:1 W) and Os coated cathode have been developed and the results are presented. The cathodes made out of this alloy coating showed 1.5 times higher emission and 0.02 eV emission uniformity as compared to those of simply Os coated cathodes which can be used in terahertz devices application.

A novel synthesis approach for scandia-doped tungsten nano-powder using a sol–gel method is developed. It involves dissolving tungsten oxide at 300 °C in the presence of a mixture of nitric acid, citric acid and ammonia. The dissolved tungsten oxide reacts with an aqueous solution of scandium nitrate in the liquid–liquid phase, which results in the homogeneous mixing of tungsten and scandium particles. A spherical shape particle was obtained due to the dissolving of tungsten oxide in the solution. Citric acid enhances the mixing of ions at the atomic scale, which affects the hydrolysis reactions and leads to the formation of the phase pure nano-particle. The synthesized nano-powder was characterized by SEM (Scanning Electron Microscopy), EDS (Energy-dispersive X-ray spectroscopy), TEM (Transmission Electron Microscopy), and XRD (X-ray Diffraction) analyses. The spherical morphology was observed via a SEM analysis and a narrow particle size distribution was noted by means of a TEM analysis. The XRD analysis of the powder showed the complete formation of the phase pure nano-particle with an average diameter of 50 nm without any contamination by other materials.

Objectives The aim of this study was to develop a new method to measure the polymerization shrinkage of light cured composites and to evaluate the overall utility and significance of the technique. Methods An optical instrument to measure the linear polymerization shrinkage of composites without directly contacting the specimen was developed using a particle tracking method with computer vision. The measurement system consisted of a CCD color video camera, a lens, an image storage device, and image processing and analysis software. The shrinkage kinetics of a commercial silorane-based composite (P90) and two conventional methacrylate-based composites (Z250 and a flowable Z350) were investigated and compared with the data measured using the “bonded disc method”. Results The linear shrinkage of the composites was 0.33–1.41%. The shrinkage value was lowest for the silorane-based (P90) composite and highest for the flowable Z350 composite. The estimated volume shrinkages of the materials were comparable to the axial shrinkages measured with the bonded disc method. Significance The new instrument was able to measure the true linear shrinkage of composites without sensitivity to the specimen geometry and the viscosity of the material. Therefore, this instrument can be used to characterize the shrinkage kinetics for a wide range of commercial and experimental visible-light-cure materials in relation to the composition and chemistry.

Objectives The aim of this study was to investigate the influence of shrinkage strain, modulus, and instrument compliance on the polymerization shrinkage stress measurement of light-cured composites, and to determine whether the silorane-based low-shrinkage composite shows a low-polymerization shrinkage stress. Methods A universal hybrid; Z250 (Z2), a flowable; Z350 (Z3), and a silorane-based; P90 (P9) composite was examined. A modified “bonded disc method” was used to measure the axial shrinkage strain of the composite. For the measurement of the initial modulus development of composites during light curing, a dynamic oscillatory shear test was undertaken using a custom-made oscillation rheometer. A frequency of 6 Hz and strain amplitude of 0.0091 rad for 20 s was employed and the complex shear modulus ( G * ) was determined. A newly designed stress–strain analyzer was made to measure the shrinkage stress of the composites with two modes: (1) high compliance, or (2) low compliance. The shift between the two modes was controlled by an On–Off switch of a negative feedback circuit. Theoretical shrinkage stress was calculated from the shrinkage strain and modulus measured above, and compared with experimentally measured stress. Data were analyzed with one-way ANOVA and Tukey's post hoc test ( α = 0.05), and correlation analysis was done to investigate the relationship between measured stress and shrinkage strain, modulus, and theoretical stress. Results The shrinkage strain of Z3 (4.12%) at 10 min was the highest, followed by Z2 (2.31%) and P9 (0.77%). At 10 s after light curing, Z2 showed the highest modulus (466.2 MPa), Z3 (154.1 MPa), and P9 the lowest (130.7 MPa). The measured stresses with low compliance were much higher than those with high compliance. With high compliance, the contraction stress of Z3 was the highest (2.75 MPa), followed by Z2 (1.54 MPa) and P9 (0.48 MPa). In low-compliance mode, the stresses of Z3 (7.93 MPa) and Z2 (7.48 MPa) were similar ( p = 0.323) while the stress of P9 (3.23 MPa) was much lower. A strong correlation was observed between the theoretical stress and the measured stress with low compliance ( R = 0.996). In high-compliance mode, the shrinkage strain also showed a near-linear relationship with the stress measured ( R = 0.937), but the modulus showed a low correlation with the measured stress ( R = 0.398). Significance Depending on the instrument compliance, polymerization shrinkage stress showed significant differences for each material. In high-compliance shrinkage strain played a greater role, while in low-compliance shrinkage strain and elastic modulus contributed comparably in determining the shrinkage stress. The low-shrinkage silorane-based composite demonstrated considerable reduction in shrinkage strain and stress.

Mode conversion of high-power electromagnetic microwave (HPEM) was successfully accomplished using a coaxial-beam rotating antenna (COBRA) in an X-band relativistic backward-wave oscillator (RBWO). The mode conversion from the TM01 mode to the circularly polarized TE11-likeness mode was identified by both cold test and hot test. To observe whether mode conversion is effective or not, the radiation pattern of TE11-likeness mode by COBRA lens was compared with the case of the radiation pattern of TM01 mode using simple horn antenna. Their radiation patterns could be described by fluorescent lamps. The experimental results of radiation pattern measurements are shown to be in a reasonable agreement with the simulated one. The maximum value of RF output power appeared at the center of COBRA lens from the experimental results.

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.

Equilibrium molecular dynamics (EMD) simulations are used to evaluate the transport coefficients of argon-krypton mixtures at two liquid states (state A: 94.4 K and 1 atm; state B: 135 K and 39.5 atm) via modified Green-Kubo formulas. The composition dependency of the volume at state A obeys close to the linear model for ideal liquid mixture, while that at state B differs from the linear model probably due to the high pressure. The radial distribution functions for the Ar-Kr mixture (x = 2/3) show a mixing effect: the first peak of g 11 is higher than that of g(r) for pure Ar and the first peak of g 22 is lower than that of g(r) for pure Kr. An exponential model of engineering correlation for diffusion coefficient (D) and shear viscosity (η) is superior to the simple linear model for ideal liquid mixtures. All three components of thermal conductivity (λ pm , λ tm , and /λ ti ) at state A and hence the total thermal conductivity decrease with the increase of x. At state B, the change in λ tm is dominant over those in λ pm and λ ti , and hence the total thermal conductivity decrease with the increase of x.

Modified metallic metamaterials are known to provide external radiation from Cerenkov-like modes which can be excited using an electron bunch. Extremely strong electromagnetic field enhancement could be formed for compact, efficient free-electron lasers with open metallic structures. The numerical and experimental works will be presented in detail.

The suppression of TE mode oscillations in a PPM-focused S-band sheet beam klystron amplifier using a method of loading distributed losses is presented. This method allows us to make a reasonable attenuation of unwanted modes relative to the operating TM mode and can be used to improve the stability of beam-wave interaction circuit with high aspect ratio.