A major challenge for glass X-ray tube makers is the reduction in the tube size for portable or handheld applications. Size reduction is difficult mainly due to contact size restrictions for glass-to-metal welding. In high-voltage (60-70 kV) portable applications such as dental imaging, a distance of at least 5 mm should be maintained between the anode and the glass envelope to prevent the latter from burnout, which further limits reduction in the tube's diameter. In this study, reduction in the size of a dental X-ray tube by approximately 43% is achieved by replacing the glass envelope with ceramic. Instead of welding, the ceramic body permits the use of brazing, which supports extremely small contact sizes. Additionally, due to the higher dielectric constant of ceramic, even less than 1 mm spacing is permissible between the envelope and the anode, enabling further size reduction. Despite the 43% reduction in size, limiting spatial resolutions of approximately 8 and 7 lines per mm are obtained for the ceramic and glass sealed tubes, respectively. Moreover, the two tubes obtain similar X-ray images of human teeth, verifying the potential of the compact-size ceramic X-ray tube in dental imaging.

The recent increase in ailments has increased the demand for diagnosis and surgery based on X-rays. An X-ray system using a filament-type tube heats the filament for operation, and the electrons emitted by the thermal energy during this process produce X-rays. Conventionally, current control-based methods are used to regulate heating. However, these methods do not control the temperature of the filament, resulting in lower or higher output than the desired dose rate. Therefore, we propose a filament temperature control method that enables constant temperature control, which cannot be achieved using the existing heating method for X-ray systems with filament tubes. Additionally, we developed an indirect temperature estimation algorithm for the tungsten filament to incorporate the proposed method. To validate the tube current control through temperature control, we performed experiments to compare the existing current-controlled heating and temperature control methods in terms of the filament temperature. As the tube current is proportional to the dose rate, it was measured through a comparative analysis of the change in the output of dose rate over time. The obtained results validate that the proposed method can maintain both the filament temperature and tube current at the desired level.

In recent years, there has been a trend toward expanding the operating frequency range and increasing the output power of Sound Navigation and Ranging (SONAR) systems to enhance their acoustic detection capabilities. However, due to this increase in operational power, the electrical capacity of amplifiers for SONAR system operation also increases, necessitating High-Power Amplifiers. When configured with a single amplifier, as in conventional methods, the volume of amplifiers increases due to volumetric increases in heat dissipation, components, and windings. These issues are detrimental to SONAR amplifier installation, mobility, maintenance, and equipment lifespan due to stress on individual components. Additionally, amplifiers for SONAR systems are comprised of power conversion devices, transformers for LC filters and matching, necessitating consideration of LC filters and matching transformers for enhancing voltage quality and efficiency to improve amplifier performance transmitted to SONAR transducers. However, previous research has focused on single-amplifier design methods, neglecting such considerations. Therefore, this paper proposes a design technique that overcomes the drawbacks of using the conventional design method by configuring multiple H-bridge inverters in a cascade format and utilizes one of the optimization algorithms, Particle Swarm Optimization (PSO), to derive amplifier design techniques that optimize component parameters for enhancing high-capacity amplifier performance. Subsequently, theoretical analysis, simulations, and experimental results comparing the proposed high-power amplifier design method with conventional single-amplifier design methods demonstrate similar error rates in operational frequency bands.

Improving the operational efficiency and optimizing the design of sound navigation and ranging (sonar) systems require accurate electrical equivalent models within the operating frequency range. The power conversion system within the sonar system increases power efficiency through impedance-matching circuits. Impedance matching is used to enhance the power transmission efficiency of the sonar system. Therefore, to increase the efficiency of the sonar system, an electrical-matching circuit is employed, and this necessitates an accurate equivalent circuit for the sonar transducer within the operating frequency range. In conventional equivalent circuit derivation methods, errors occur because they utilize the same number of RLC branches as the resonant frequency of the sonar transducer, based on its physical properties. Hence, this paper proposes an algorithm for deriving an equivalent circuit independent of resonance by employing multiple electrical components and particle swarm optimization (PSO). A comparative verification was also performed between the proposed and existing approaches using the Butterworth–van Dyke (BVD) model, which is a method for deriving electrical equivalent circuits.

The carbon nanotube (CNT) field emitter is suitable for the high frequency pulsing of X-ray. Pulsing reduces 49% of the dose in grid-controlled fluoroscopy and improves the image of moving objects. Various structures and manufacturing processes are being studied. However, more studies on the dynamic characteristic of a pulsing CNT and its application are needed. In this study, the combined dynamics including the field emission, MOSFET, and modified gate driver for MOSFET have been analyzed. In this configuration, between the cathode of the tube and ground, there is a MOSFET switch that turns the tube current on/off and a shunt resistor that measures the tube current. Due to the high impedance of the vacuum between the gate and cathode of the tube, about 85% of the gate voltage is still exerted between the Gate and cathode of the tube during the off-state of the MOSFET. Therefore, space charges are built during the off-state and then released at the beginning of the on-state of the MOSFET. The modified gate driver structure for MOSFET that we propose in this paper can limit the amount of current flow through the cathode. Tube current (boosted current) can be accurately controlled through a modified gate driver structure. Combining the boosted current and pulse control of MOSFET, the dynamic current performance of a CNT tube can be enhanced and the average tube current or dose can be accurately controlled. Experiments, simulation, and analysis have been conducted to study the combined dynamics and its applications.