High Power Operation Research Articles

An investigation of n-type semiconductors based on optical and photoluminescence of pure and Al doped Pr:123 compound

With ZnO comparison, we report here an investigation of n-type semiconductors in terms of optical and photoluminescence (PL) analysis based on PrBa2Cu3-3xAl3xOy (AlPr:123) compound with (0.00 ≤ x ≤ 1.00). The structure is tetragonal of the samples with x ≤ 0.30 and changes to orthorhombic for x > 0.30, whereas it is wurtizite (hexagonal) for ZnO. As x increases to 1.00, the grain size is decreased, while the crystallite size and porosity are increased, but they are comparable with those obtained for ZnO. The Debye temperature, Young’s modulus and energy gap are drastically decreased by increasing x until reach to their maximum values of 623.14 K, 952 GPa and 3.45 eV for x = 1.00 (650.39 K, 17 GPa and 3.28 eV for ZnO). The x = 0.05 has increased the carrier density to 8.06 × 10 19 (cm−3), which is about 8-times higher than of ZnO (1.07 × 10 19 (cm −3). The highest value of q-factor (3.5 × 10 5) is obtained for x = 0.00, which is about 10-tims higher than of ZnO (3 × 10 4). As x increases above 0.30, the optical conductivity is significantly increased to be greater than that of ZnO. The PL intensity of the visible emission peaks was gradually increases against x until becomes higher than that of ZnO when x = 1.00. A slight UV shift is obtained for x ≤ 0.30 samples, but it changed to blue for x ≥ 0.60, which is typically similar to ZnO. As compared to ZnO, the present samples are strongly recommended for plastic deformation, solar cell, light emission, super-capacitor and high-power operation. To the best of our knowledge, the present work has never been done elsewhere.

Static Approximate Modified Mirror—Full Adder for High Speed and Low Power Operations Using 32 nm CNTFET Technology

ABSTRACTThe error tolerance nature of the digital multimedia applications enables the implementation of approximate digital circuits to achieve the benefits of high speed of operation and low power consumption. This paper proposes a static approximate modified mirror full adder (SAMM‐FA) circuit designed using logic level approximation to reduce the number of transistors in the circuit. Owing to the balanced electrical characteristics, better stability and higher on‐current to off‐current ratio (Ion/Ioff), 32 nm carbon nanotube field effect transistor (CNTFET) technology has been used for implementing the proposed circuit in the Cadence Virtuoso tool. Featuring only 10 transistors and operating at a supply voltage of 0.5 V, the proposed SAMM‐FA has a low power dissipation of just 4.14 nW, and propagation delay of just 3.82 ps. The power delay product and energy delay product figure of merits of the proposed circuit are found to be excellent when compared with the contemporary designs.

Novel electriferous charge-mosaic S(TMC@Lys-Li) separator towards efficient Li+ fast-transfer for high-energy density and long-duration lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries with attractive capacity give remarkable potential for prospective high-capacity application scenarios but suffer a fatal flaw of short cyclability before large-scale commercialization especially owing to polysulfide (Li2Sn) transmembrane shuttling. To efficiently restrain chronic Li2Sn shuttle and expedite Li+ transfer, herein, a novel electriferous charge-mosaic S(TMC@Lys-Li) separator preparation approach is recommended. Interfacial polymerizations of lithiated lysine and trimesoyl chloride establish an electriferous charge-mosaic polyamide functional layer. Substituted Li within the charge-mosaic layer offers transition or replacement sites for smoothing Li+ migrations, which constructs efficient Li+ fast-transfer private channels and accelerates the Li+ transfer rate to 9.4 times. Negatively charged polyamide skeleton synchronously heightens Li2Sn rejections by combining Donnan and steric effects. S(TMC@Lys-Li) replenishes Li for homogenizing Li nucleation and growth, endowing stable plating/stripping behaviors over 250 cycles for Li-Cu batteries. Assembled Li-S cells thus exhibit excellent specific capacity and cyclability at multiple application scenarios such as long periods, high areal capacity, and fast charge, holding 78.1% retention after 500 cycles at 1 C. The superior thermal stability and self-discharge of S(TMC@Lys-Li) dramatically strengthen battery thermal runaway resistance even at 155 ℃, which ensures security for Li-S battery high-power and high-temperature operations. Above alluring features enable charge-mosaic separators to be potentially adopted in practical Li-S batteries demanding strict security, high-capacity density, and fast charge technology.

Design of a high power combiner in HF band

Power combiners are commonly used in power amplifiers to achieve high power, especially in long-range and medium-range wireless communication device transmission systems. This paper proposes designing and implementing a high-power two-way power combiner operating in the HF (High Frequency) band, aiming to achieve an output power of over 1 kW. The power combiner is designed, implemented, and tested in the laboratory with the following achieved parameters: insertion loss between output and input better than 3.4 dB and isolation between inputs better than 26 dB. The experimental results showed that the proposed power combiner had better performance than existing combiners on the market. Mainly, power combining efficiency is over 88%, the standing wave ratio at ports is less than 1.25, and the operating temperature of the power combiner is less than 50 °C, meeting the set requirements.

High-Power, High-Beam-Quality, Long-Pulse-Width 532 nm Laser Based on a 4f Optical System

In response to the demand for high-power, long-pulse-width 532 nm lasers in the medical and industrial processing fields, this paper explains how the laser cavity of a high-power Nd:YAG 532 nm laser can be extended while maintaining the laser’s q-parameter by using a 4f optical system. The results show that at a repetition rate of 10 kHz, the extended cavity achieved a maximum average power of 112 W. Compared with the short cavity, the power was not significantly reduced. The pulse width was extended from 56 ns to 85 ns, and its broadening ratio reached 46.5%. The laser maintained good beam quality during high-power operation.

Negative Joule heat effect on supercapacitor module

Joule heat as the main heat source in high-power operation of supercapacitor modules, needs to be carefully considered in thermal management. The sufficient discussion on the temperature characteristics of supercapacitor modules, especially those containing auxiliary electronic components during operation is of importance. Here we reported the Joule heat effect on a supercapacitor module integrated on a circuit board in the charge and discharge cycles by an in situ Infrared imaging method. Temperature rise of total components including wires, circuit board, welding pint, resistor and capacitor cell could be simultaneously imaged with a sensitivity of 0.2–0.3 °C. Upon charge–discharge cycles from 5C-60C, Joule heat on these electronic components was discovered. The thermal transfered from the connected wires to the circuit board and finally to the cell, which significantly increased the temperature rise (from 9.3 °C to 19.6 °C at 60C) and temperature difference (9.6 °C at 60C) of different capacitors in modules. Further simulation results indicated that Joule heat on the circuit board was 2–3 times that of the capacitors in the module. Such additional heat flow without suitable cooling system would result an accelerated capacitance decay of the module. Therefore, a suitable module structure and thermal management strategy needed to be designed to minimize the Joule heat generation of such electronic components.

Sub-THz and THz Cherenkov radiation source with two-dimensional periodic surface lattice and multistage depressed collector

We present the theory, concept and design of an efficient, megawatt coherent Cherenkov radiation source based on a two-dimensional periodic surface lattice (2D-PSL) cavity combined with a novel energy recovery system for the generation of highly efficient (> 50%) single-frequency radiation. We demonstrate the scalability of the transverse dimension of the 2D-PSL cavity of the Cherenkov source and thus the potential for efficient, continuous-wave, high-power (> 1 MW) operation; fundamental to the eventual realization of clean, fusion energy. These new sources, with the capacity to operate in the 0.1-10THz range, hold strong promise to address the long-standing “Terahertz gap”. By combining a Cherenkov oscillator driven by a non-gyrating beam with an innovative four-stage depressed collector energy recovery system, the overall device efficiency can be increased to be competitive with gyrotrons in the requirements for heating and current drive in fusion plasma. In these Cherenkov devices, the frequency independence of the magnetic guide field enables advantageous frequency scaling without deployment constraints, making them especially attractive for high-impact applications in fusion science, turbulence diagnostics, non-destructive testing and biochemical spectroscopy. The novel energy recovery techniques presented in this paper have broad applicability to many electron-beam driven devices, bringing revolutionary potential to future THz source technologies.

Comparative study of optical properties and photocatalytic performance of Cd0.4Mn0.6O nanocomposites incorporated with different metal oxides

The structural, optical, and photocatalytic properties of Cd0.4Mn0.6XO nanocomposites with 50 wt% of X were investigated (X denotes ZnO, SnO, CuO, Al2O3, Fe2O3, NiO, and CoO). The crystal structure of Cd0.4Mn0.6XO nanocomposites is composed of the monoclinic Cd2Mn3O8 phase, along with other individual phases dependent on the type of X dopant. The crystallite sizes are between 11.07 nm for CoO and 23.65 nm for ZnO, whereas the particle sizes are between 9.75 nm for ZnO and 35.61 nm for Fe2O3. The SnO, NiO, and CoO nanocomposites had the highest values of the effective surface area of 29.71, 26.3, and 24.1 m2/g, respectively. The NiO and SnO nanocomposites had the highest and lowest absorbance, respectively, notably at wavelength below 400 nm. SnO, NiO, CuO, and Fe2O3 nanocomposites have the highest values of energy gap (Eg > 2 eV), whereas CoO, ZnO, and Al2O3 nanocomposites have the lowest Eg values (<2 eV). The SnO nanocomposite exhibited the highest values of refractive index, q-factor, lattice dielectric constant (εL), free carrier density (Nm∗), and optical/electrical conductivity when compared to the other Cd0.4Mn0.6XO nanocomposites. Interestingly, the values of εL, and Nm∗ were enhanced to 21.2 and 4.9 × 1057 cm−3g−1 for SnO nanocomposite, followed by NiO and Fe2O3 nanocomposites. The photodegradation efficiency towards methylene blue (MB) using the Cd0.4Mn0.6XO catalysts after 3 h of irradiation equals 97.94, 76.43, 74.43, 71.32, 65.98, 62.86, and 48.55 % for ZnO, NiO, SnO, Fe2O3, Al2O3, CuO and CoO nanocomposites, respectively. The photocatalytic performance of Cd0.4Mn0.6XO catalysts towards MB was compared to earlier investigations and a scavenger test was performed to validate the formation of reactive oxygen species. The features of Cd0.4Mn0.6XO nanocomposites are convenient for light-emitting diodes, solar cells, reduced electronic noise, high-power operation, and water purification.

Reactive extrusion for efficient preparation of high temperature resistant PA6T/66/BN composites with great thermal management and mechanical properties

High temperature resistant polymer-based composite with high thermal conductivity and great mechanical properties are highly demanded in the field of electronic devices for simultaneously meeting surface mounting process and high-power operation. The key to achieving this goal is to balance the contradiction between the high melt viscosity of high-temperature resistant polymers and the dispersibility of fillers. In this work, the high-performance polyamide 6T/66/hexagonal boron nitride (PA6T/66/BN) composites were fabricated successfully via the method combining prepolymerization and reactive extrusion. Results demonstrated that this method not only significantly improves the preparation efficiency of high temperature resistant polyamide and its composites, but also enables the prepared composites to reach 3.6 W/(m⋅K), over 299 °C and 67.8 MPa in thermal conductivity, melting point and tensile strength respectively. Furthermore, the prepared composite exhibits excellent thermal management effects on LED and CPU. Therefore, the results of this work are of great significance for the efficient preparation and wide application of high-temperature resistant polymer based thermally conductive composites.

Innovative flow field design strategies for performance optimization in polymer electrolyte membrane fuel cells

This study introduces an innovative flow field design methodology that departs from traditional approaches, aiming to simplify design variables and ensure an efficient, automated design process. This methodology integrates topology optimization, the Gray-Scott reaction/diffusion system, and Murray's law to design the flow field layout. We applied this methodology to the flow field design of Polymer Electrolyte Membrane Fuel Cells (PEMFC) bipolar plates. Specifically, the optimal two-dimensional pattern of the PEMFC cathode flow field was achieved by merging topology optimization with the Gray-Scott reaction/diffusion system. Applying Murray's law, an optimal three-dimensional flow field with an unpredictable new pattern was established. The design emphasizes efficient fuel diffusion and reduced flow resistance, validated through experiments. Quantitative comparisons with serpentine and parallel flow fields showed performance differences of approximately 60 mV and 120 mV at a current density of 1.43 A/cm2, respectively. These metrics reflect the impact on mass transfer efficiency under high-power PEMFC operations, serving as critical indicators of flow field effectiveness. Additionally, simulations confirmed an 18-fold reduction in pressure drop compared to the serpentine design. This innovative design process offers advantages that could be incorporated into diverse research areas in the future.

Recent progress of JT-60SA project toward plasma operation

Abstract Superconducting tokamak JT-60SA plays an essential role in fusion research and development by supporting and complementing ITER project, providing directions to the DEMO design activity and fostering next generation scientists and engineers. Since the incident of the Equilibrium Field coil #1 during the Integrated Commissioning (IC) in March 2021, both EU and JA Implementing agencies (IAs) have examined how to ensure safety operation of JT-60SA by mitigating the risk of possible discharge occurrence inside the cryostat. Based on the experience of the Global Paschen tests, the IAs have established a strategy of risk mitigation measures, which is a combination of (i) reinforcement of insulation, (ii) avoiding unnecessary voltage application to the coil systems and (iii) immediate de-energization of the coils when deteriorated vacuum condition is detected. Thanks to the considerable efforts of the Integrated Project Team (IPT) members, the IC restarted in May 2023. After the confirmation of superconducting state of coil systems (TF, EF and CS), the coil energization test and the plasma operation (OP-1) starts. The first plasma was successfully achieved on 23 October 2023 with a limited value of applied voltage and current to the coils. The plasma configuration control will be also confirmed with low plasma current and low auxiliary heating power conditions. Based on the IO-F4E-QST collaboration, activities of JT-60SA have been shared with the IO and provided an important lesson learned for ITER assembly and commissioning, and will provide an outstanding contribution to fusion research at large. After OP-1, Maintenance &amp; Enhancement phase 1 (M/E-1) starts from January 2024, in which in-vessel components are installed, and heating system and diagnostic system are extensively upgraded to allow high power heating experiment planned in OP-2. In order to make the best use of JT-60SA, newly organized JT-60SA experiment team will refine the research plan in the future high heating power operation phase.

A novel sensor preference method for proton exchange membrane fuel cell flooding fault diagnosis based on multi-algorithm

ABSTRACT During periods of high-power operation, proton exchange membrane fuel cell (PEMFC) produce water, which gradually accumulates at the cathode. It causes flooding faults and significantly impacts on PEMFC safety. The data collected by the sensors is a fundamental prerequisite for the flooding faults diagnosis in PEMFC. Consequently, it is critical to select sensors. However, the conventional methods for selecting sensors consider sensitivity and noise immunity, the number of sensors selected and the flood diagnostic performance are not optimized. To solve the above problems, this paper proposes a sensor preference method that combines the Mantel test and Spearman coefficient (MS method). This method first uses the Mantel test to analyze the correlation between two flooding evaluation indicators and the sensors, it identifies suitable sensors for diagnosing flooding faults. Subsequently, the Spearman coefficient eliminates redundant sensors. Additionally, a one-dimensional convolutional neural network is employed to construct a flooding diagnosis model. The MS method is contrasted with two traditional sensor selection methods. The results show that the MS method selected sensors yield superior model training and enhanced accuracy in diagnosing flooding, thereby ensuring PEMFC safety.

Operational Characteristics of AlGaN/GaN High-Electron-Mobility Transistors with Various Dielectric Passivation Structures for High-Power and High-Frequency Operations: A Simulation Study.

This study investigates the operational characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) by employing various passivation materials with different dielectric constants and passivation structures. To ensure the simulation reliability, the parameters were calibrated based on the measured data from the fabricated basic Si3N4 passivation structure of the HEMT. The Si3N4 passivation material was replaced with high-k materials, such as Al2O3 and HfO2, to improve the breakdown voltage. The Al2O3 and HfO2 passivation structures achieved breakdown voltage improvements of 6.62% and 17.45%, respectively, compared to the basic Si3N4 passivation structure. However, the increased parasitic capacitances reduced the cut-off frequency. To mitigate this reduction, the operational characteristics of hybrid and partial passivation structures were analyzed. Compared with the HfO2 passivation structure, the HfO2 partial passivation structure exhibited a 7.6% reduction in breakdown voltage but a substantial 82.76% increase in cut-off frequency. In addition, the HfO2 partial passivation structure exhibited the highest Johnson's figure of merit. Consequently, considering the trade-off relationship between breakdown voltage and frequency characteristics, the HfO2 partial passivation structure emerged as a promising candidate for high-power and high-frequency AlGaN/GaN HEMT applications.

Dynamic modeling of polymer electrolyte membrane fuel cells under real-world automotive driving cycle with experimental validation on segmented single cell

A 1+1D transient non-isothermal and multiphase polymer electrolyte membrane fuel cell model is developed. The model is validated on experimental data gathered on a segmented single cell and representative of a real-world automotive driving cycle, derived from the stack protocol defined in the ID-FAST H2020 project. During Low-Power operation, cell voltage response is mainly controlled by platinum oxide and water dynamics: the low hydration significantly affects cathode inlet performance. Throughout High-Power operation, instead, voltage transients are ascribable to local mass-transport related phenomena: in particular, liquid water accumulation along the channel strongly decreases the efficiency of cathode outlet region. Finally, the effect of relative humidity at cathode channel inlet is investigated: an increase in the humidification of the air inlet stream from 30% to 50% leads to a better proton conductivity and, therefore, to a significant enhancement of the performance of cathode inlet regions, which also means a slight improvement in the average stack efficiency from 62.2% to 62.8%. Lowering RH of the air-inlet stream from 30% to 15%, a worsening of proton conductivity is observed, which exacerbates performance heterogeneities and leads to a reduction of the average stack efficiency from 62.2% to 61.5%, consistently with experimental results.

(Invited) Ga2O3 Semiconductor Devices for High-Temperature Operation

Beta phase of gallium oxide (Ga2O3) has attracted a lot of attention as an ultra-wide band gap semiconductor for applications in high-power electronic devices. High power operation often comes with increased temperatures of the devices due to joule heating, especially in semiconductors like Ga2O3with low thermal conductivity. However, electrical performance and reliability of the Ga2O3based diodes and transistors at very high temperature, above 400C, is not well established.In this talk, I will present our recent experimental results on fabrication of Ga2O3semiconductor devices for applications as high-temperature diodes and hydrogen gas sensors. The fabricated Ga2O3/NiO p-n heterojunctions allow for device operation with >100-1000 rectification ratio up to 400-600C [1]. Despite the stable ultrathin Ohmic contact [2], the device performance degrades over tens of temperature cycles and hundreds of hours at these elevated temperatures, likely due to instability of the rectifying contact. We propose and implement alternative interfacial rectifying contact layers, that enable both high performance and long reliability of these high temperature Ga2O3 semiconductor devices.[1] Sohel, Zakutayev et al Physica Status Solidi (a) 220 2300535 (2023)[2] Callahan, Zakutayev et al J. Vac. Sci. Technol. A 41, 043211 (2023)

The 2-Propanol Fuel Cell: Direct CO2-Free Electrification with a Liquid Hydrogen Carrier

Molecular hydrogen is a gas at ambient conditions and requires compression or cryogenic liquefaction for storage and transport, leading to significant losses in efficiency. Therefore, liquid hydrogen carriers are desirable as they are storable without losses. One such fuel that has shown promise recently is 2-propanol (isopropanol), which is converted with high selectivity to acetone in a fuel cell.[1],[2],[3] Power densities over 200 mW/cm2 have been reported for direct isopropanol fuel cells (DIFCs), which rivals the best direct methanol fuel cells (DMFCs), and unlike methanol, isopropanol is non-toxic and it is not fully oxidized to CO2. [4] The literature has demonstrated many advantages of DIFCs, yet significant challenges remain.[5] Continuous operation at high current densities can be limited due to anodic catalyst layer network effects: slow removal of acetone from active sites and out of the catalyst layer. Additionally, perfluorinated sulfonic acid (PFSA) ionomers are not fully chemically compatible with 2-propanol and acetone. Operation at higher temperatures with a vaporized 2-propanol feed partially mitigates both of these disadvantages, yet the high energy cost of vaporization reduces the overall efficiency of the system. Future research should focus on stable, high-power operation with a liquid 2-propanol feed.This contribution chronicles the progress that has been made and discusses the current state-of-the-art and outlook of direct electrification with DIFCs. Recent advances in liquid-fed DIFCs are presented, including design of membrane-electrode-assemblies and operation strategies in full cells. Finally, the concept of using the 2-propanol/acetone couple as an electrochemical liquid organic hydrogen carrier is briefly introduced: a reversible hydrogenation and dehydrogenation cycle for storing and releasing molecular hydrogen on demand.

Elucidating the Electrochemical Impact of the Calendering Process on Three-Dimensional Designed Electrodes for Lithium-Ion Batteries

Significant advancements in battery technology are imperative to meet the ambitious demands for electromobility and stand-alone energy storage devices. This stems from the need to achieve operations with high energy and power density, coupled with stringent safety standards and extended lifespans, while reducing production and material costs. The preferred energy storage technology for the coming decade is anticipated to remain lithium-ion battery (LIB) technology. The focus on researching high-energy active materials to optimize this technology is paramount. In addition to optimizing materials, significant performance enhancements can be achieved by using electrodes with high mass loading and a multiscale tailored electrode design that can be scaled up to production level.The technological challenges of achieving a breakthrough in gaining simultaneously high energy and power density characteristics while maintaining high process and operational reliability with significant cost savings are the subject of current research and development in the field of LIB technology. To tackle this, the study explores the laser-assisted generation of three-dimensional (3D) electrode architectures and assesses its impact on battery performance and future integration into battery production. The advanced electrode design involves micro and sub-micron structures that can be tailored in various ways, leading to notable improvements in battery lifespan, battery safety, and fast charging and high-power operation capabilities compared to batteries with conventional two-dimensional (2D) electrodes. High-power ultrafast laser ablation emerges as a precise method for introducing such structures.Coordinating the production of 3D electrodes with laser assistance necessitates synchronization with established manufacturing steps in the battery production process. Notably, the calendering of electrodes holds significance due to its substantial influence on the microstructural properties of the electrode material, encompassing porosity, material density, and layer adhesion. The study investigates the impact of laser-induced structuring, encompassing micro-/nano-porosities and microtopography, on electrodes with varying mass loadings ranging from 2mAh/cm² to 6mAh/cm². Electrochemical characteristics such as high-rate capability, fast charging, and cycle lifetime are evaluated accordingly, employing cells with graphite anodes and lithium-nickel-manganese-cobalt oxide cathodes.

Benchmark and Roadmap for Low Temperature Water Electrolysis for Green H2 Production and Applications

Water electrolysis has attracted world-wide attention due to its ability to produce green hydrogen when coupled with renewable electricity. Green hydrogen is a viable solution to decarbonizing a variety of industries including fertilizer, metal production, petrochemical, and synthetic fuels. There are three major low temperature water electrolysis technologies, alkaline water electrolyzer (AWE), proton exchange membrane water electrolyzer (PEMWE), and anion exchange membrane water electrolyzer (AEMWE). This work will first provide the status of these three technologies in terms of operating conditions, lifetime, and capital cost. Subsequently, the challenges and constraints for these technologies will be discussed in the scenarios of large-scale manufacturing and integration with intermittent renewables. More efforts will be made to illustrate the trajectory of the next-gen water electrolysis technologies, which feature at ultralow PGM or PGM-free catalysts, thin membranes with reduced hydrogen crossover, high-current high-power operation, long lifetime, and remarkable cost reduction. The work will also address the challenges of automated MEA fabrication and stack manufacturing at scale. Finally, a real example of renewable wind turbine integrated with water electrolyzer to produce green hydrogen and subsequently green ammonia will be demonstrated.

Multipactor analysis of 431 MHz L-shaped inductive output tube cavity

Gridless inductive output tubes (IOTs) offer compact size and high-power amplification at sub-GHz frequencies. Minimizing cavity dimensions in the interest of compactness leads to smaller gaps, which may cause multipactor discharge under high-power operating conditions. The uncontrolled electron growth resulting from multipactor breakdown can lead to undesired effects including surface damage and system failure. This paper performs a parallel-plate multipactor analysis for a high-Q, L-shaped, aluminum, 431 MHz cavity designed for a gridless IOT to be operated in the MW-power regime. The cavity gap is 27 mm, and diameter is 339 mm. Multipactor susceptibility regions are calculated for non-zero emission energy, half-cycle, and non-half-cycle multipactor using a semi-analytic approach and a standard aluminum secondary electron yield (SEY) curve. The analytical results are validated with particle-in-cell simulation in CST Studio. Simulation results show a voltage range of 6.4–19 kV, compared to the analytically calculated values of 8.2 and 18.3 kV for the lower and upper bounds, respectively. Fluorocarbon coating as a means to reduce secondary electron emission is simulated, which shows 46% reduction in peak particle population with an 11.2 nm PTFE coating, with further reduction as coating thickness increases. The results show that the L-shaped cavity is a suitable choice for this IOT design as it does not exhibit single-surface multipactor and will not develop two-surface multipactor at full-power operation.

Design optimization of a modified Uni-Traveling- carrier photodiode for high optical power operation

We systematically investigated the design optimization of an InGaAs/InP modified Uni-Traveling-Carrier Photodiode (MUTC-PD) under high optical power input conditions. Based on internally fabricated experimental devices for a baseline design, we first achieved an excellent match between our experimental and simulation results under low optical power density of 1.4 mW/μm2, demonstrating the accuracy of our simulation model. Based on this model we showed that as optical power injection increases, the intrinsic bandwidth of the MUTC-PD degradation is the primary limitation on its high-speed response. We quantitatively analyzed the fundamental carrier transport physics and key design parameters affecting intrinsic bandwidth degradation under these conditions. In particular cliff layer doping concentration was found to be a very sensitive parameter affecting the MUTC-PD Optical Electrical (OE) intrinsic bandwidth. Based on detailed simulated results, we realized an optimized device design that is capable of achieving a 3 dB bandwidth of approximately 230 GHz at 10 mW/μm2 input optical power density for the first time.